Inhibiting learned behaviours when they become unproductive and searching for an alternative solution to solve a familiar but different problem are two indicators of flexibility in problem solving. A wide range of animals show these tendencies spontaneously, but what kind of search process is at play behind their problem-solving success? Here, we investigated how Eastern grey squirrels, Sciurus carolinensis, solved a modified mechanical problem that required them to abandon their preferred and learned solution and search for alternative solutions to retrieve out-of-reach food rewards. Squirrels could solve the problem by engaging in either an exhaustive search (i.e. using trial-and-error to access the reward) or a ‘backup’ solution search (i.e. recalling a previously successful but non-preferred solution). We found that all squirrels successfully solved the modified problem on their first trial and showed solving durations comparable to their last experience of using their preferred solution. Their success and high efficiency could be explained by their high level of inhibitory control as the squirrels did not persistently emit the learned and preferred, but now ineffective, pushing behaviour. Although the squirrels had minimal experience in using the alternative (non-preferred) successful solution, they used it directly or after one or two failed attempts to achieve success. Thus, the squirrels were using the ‘backup’ solution search process. Such a process is likely a form of generalisation which involves retrieving related information of an experienced problem and applying previous successful experience during problem solving. Overall, our results provide information regarding the search process underlying the flexibility observable in problem-solving success.

Behavioural flexibility has been argued to be an evolutionarily favourable trait that helps. invasive species to establish themselves in non-native environments. But few studies have compared the level of flexibility (whether considered as an outcome or as a process) in mammalian invaders and related native species. Here, we tested whether flexibility differs between groups of free-ranging invasive Eastern grey squirrels (Sciurus carolinensis) and native Eurasian red squirrels (S. vulgaris) in the UK, using an easy and a difficult food–extraction task. All individuals of both species showed flexibility, at the outcome level, in solving the easy task and solution time was comparable between species across a series of successes. A higher proportion of grey squirrels than red squirrels solved the difficult task. However, for those squirrels that did solve the task, solving efficiency was comparable between species on their first success, and a few red squirrels outperformed the grey squirrels in subsequent successes. Between species analysis showed that instantaneous flexibility, flexibility at the process level that was measured as the rate of switching between tactics after a failed attempt, was higher in red squirrels than in grey squirrels. Within species analysis also revealed that red squirrel problem solvers showed higher flexibility at the process level, than their non-solver counterparts. Non-solvers also failed to make ‘productive’ switches (switching from ineffective tactics to effective tactics). Together, the results suggest that problem-solving ability overlaps in the two species, but is less variable, and on average higher, in grey squirrels than in red squirrels. The superior behavioural flexibility of the grey squirrels, shown here by success at problem solving, may have facilitated their invasion success, but it may also have resulted from selective pressures during the invasion process.

The great increase in the study of dog cognition in the current century has yielded insights into canine cognition in a variety of domains. In this review we seek to place our enhanced understanding of canine cognition into context. We argue that in order to assess dog cognition, we need to regard dogs from three different perspectives: phylogenetically, as carnivoran and specifically a canid; ecologically, as social, cursorial hunters; and anthropogenically, as a domestic animal. A principled understanding of canine cognition should therefore involve comparing dogs’ cognition with that of other carnivorans, other social hunters, and other domestic animals. This paper contrasts dog cognition with what is known about cognition in species that fit into these three categories, with a particular emphasis on wolves, cats, spotted hyenas, chimpanzees, dolphins, horses and pigeons. We cover sensory cognition, physical cognition, spatial cognition, social cognition, and self-awareness. Although the comparisons are incomplete, because of the limited range of studies of some of the other relevant species, we conclude that dog cognition is influenced by the membership of all three of these groups, and taking all three groups into account, dog cognition does not look exceptional.

Behavioural and cognitive processes play important roles in mediating an individual's interactions with its environment. Yet, while there is a vast literature on repeatable individual differences in behaviour, relatively little is known about the repeatability of cognitive performance. To further our understanding of the evolution of cognition, we gathered 44 studies on individual performance of 25 species across six animal classes and used meta-analysis to assess whether cognitive performance is repeatable. We compared repeatability (R) in performance (1) on the same task presented at different times (temporal repeatability), and (2) on different tasks that measured the same putative cognitive ability (contextual repeatability). We also addressed whether R estimates were influenced by seven extrinsic factors (moderators): type of cognitive performance measurement, type of cognitive task, delay between tests, origin of the subjects, experimental context, taxonomic class and publication status. We found support for both temporal and contextual repeatability of cognitive performance, with mean R estimates ranging between 0.15 and 0.28. Repeatability estimates were mostly influenced by the type of cognitive performance measures and publication status. Our findings highlight the widespread occurrence of consistent inter-individual variation in cognition across a range of taxa which, like behaviour, may be associated with fitness outcomes.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

AbstractAre the mechanisms underlying variations in the performance of animals on cognitive test batteries analogous to those of humans? Differences might result from procedural inconsistencies in test battery design, but also from differences in how animals and humans solve cognitive problems. We suggest differentiating associative-based (learning) from rule-based (knowing) tasks to further our understanding of cognitive evolution across species.

When animals encounter a task they have solved previously, or the same problem appears in a different apparatus, how does memory, alongside behavioural traits such as persistence, selectivity and flexibility, enhance problem-solving efficiency? We examined this question by first presenting grey squirrels with a puzzle 22 months after their last experience of it (the recall task). Squirrels were then given the same problem presented in a physically different apparatus (the generalisation task) to test whether they would apply the previously learnt tactics to solve the same problem but in a different apparatus. The mean latency to success in the first trial of the recall task was significantly different from the first exposure but not different from the last exposure of the original task, showing retention of the task. A neophobia test in the generalisation task suggested squirrels perceived the different apparatus as a different problem, but they quickly came to apply the same effective tactics as before to solve the task. Greater selectivity (the proportion of effective behaviours) and flexibility (the rate of switching between tactics) both enhanced efficiency in the recall task, but only selectivity enhanced efficiency in the generalisation task. These results support the interaction between memory and behavioural traits in problem-solving, in particular memory of task-specific tactics that could enhance efficiency. Squirrels remembered and emitted task-effective tactics more than ineffective tactics. As a result, they consistently changed from ineffective to effective behaviours after failed attempts at problem-solving.

We tested pigeons' acquisition of a conditional discrimination task between coloured grating stimuli that included choosing one of two response keys, which either appeared as white keys to the left and right of the discriminative stimulus, or were replicas of the stimulus. Pigeons failed to acquire the discrimination when the response keys were white disks but succeeded when directly responding to a replica of the stimulus. These results highlight how conditioning processes shape learning in pigeons: the results can be accounted for by supposing that, when pigeons were allowed to respond directly towards the stimulus, learning was guided by classical conditioning; responding to white keys demanded instrumental learning, which impaired task acquisition for pigeons. In contrast, humans completing the same paradigm showed no differential learning success depending on whether figure or position indicated the correct key. However, only participants who could state the underlying discrimination rule acquired the task, which implies that human performance in this situation relied on the deduction and application of task rules instead of associative processes.

In order to test how flexibly animals are able to behave when making trade-offs that involve assessing constantly changing risks, we examined whether wild Eastern grey squirrels showed flexibility of behavioral responses in the face of variation in two conflicting risks, cache pilferage and predation. We established that cache pilferage risk decreased with distance from cover, and was thus negatively correlated with long-term predation risk. We then measured changes in foraging and food caching behavior in the face of changes in the risk of predation and food theft over a short time-scale. We found that, overall, squirrels move further away from the safety of cover when they cache, compared to when they forage, as predicted by pilferage risk. However, there was no effect of immediate pilferage or predation risk (i.e. the presence of potential predators or pilferers) on the distance from cover at which they cached, and only a slight increase in forage distance when predation risk increased. These results suggest that ‘rules of thumb’ based on static cues may be more cost-effective for assessing risk. than closely tracking changes over time in the way suggested by a number of models of risk assessment.

To fully understand how problem solving ability provides adaptive advantages for animals, we should understand the mechanisms that support this ability. Recent studies have highlighted several behavioural traits including persistence, behavioural variety and behavioural/cognitive flexibility that contribute to problem solving success. However, any increment in these traits will increase time and energy costs in natural conditions, so they are not necessarily advantageous. To examine how behavioural traits vary during learning to solve a problem efficiently, we gave grey squirrels (Sciurus carolinensis) a problem solving task that required squirrels to obtain out-of-reach but visible hazelnuts by making a lever drop in the laboratory. We recorded persistence, measured as attempt rate, flexibility, measured as the rate of switching between tactics, and behavioural selectivity, measured as the proportion of effective behaviours, in relation to problem solving efficiency on a trial-by-trial basis. Persistence and behavioural selectivity were found to be directly associated with problem solving efficiency. These two factors also mediated the effects of flexibility and increased experience. We also found two routes that led to more efficient problem solving across learning trials: increasing persistence or increasing behavioural selectivity. Flexibility was independent from learning. Flexibility could increase problem solving efficiency, but it also has a time cost; furthermore it seemed to involve a trade-off with behavioural selectivity, with high flexibility being associated with a higher frequency of some disadvantageous ineffective behaviours. These results suggest that flexibility is an independent cognitive process or behavioural trait that may not always bring advantages to animals.

Human performance in task-switching paradigms is seen as a hallmark of executive-control processes: switching between tasks induces switch costs (such that performance when changing from Task a to Task B is worse than on trials where the task repeats), which is generally attributed to executive control suppressing one task-set and activating the other. However, even in cases where task-sets are not employed, as well as in computational modelling of task switching, switch costs can still be found. This observation has led to the hypothesis that associative-learning processes might be responsible for all or part of the switch cost in task-switching paradigms. To test which cognitive processes contribute to the presence of task-switch costs, pigeons performed two different tasks on the same set of stimuli in rapid alternation. The pigeons showed no sign of switch costs, even though performance on trial N was influenced by trial N-1, showing that they were sensitive to sequential effects. Using Pearce's (1987) model for stimulus generalisation, we conclude that they learned the task associatively - in particular, a form of Pavlovian-conditioned approach was involved - and that this was responsible for the lack of any detectable switch costs. Pearce's model also allows us to make interferences about the common occurrence of switch costs in the absence of task-sets in human participants and in computational models, in that they are likely due to instrumental learning and the establishment of an equivalence between cues signalling the same task.

It is widely accepted in European culture that magpies (Pica pica) are unconditionally attracted to shiny objects and routinely steal small trinkets such as jewellery, almost as a compulsion. Despite the long history of this folklore, published accounts of magpies collecting shiny objects are rare and empirical evidence for the behaviour is lacking. The latter is surprising considering that an attraction to bright objects is well documented in some bird species. The present study aims to clarify whether magpies show greater attraction to shiny objects than non-shiny objects when presented at the same time. We did not find evidence of an unconditional attraction to shiny objects in either captive or free-living birds. Instead, all objects elicited responses indicating neophobia in free-living birds. We suggest that humans notice when magpies occasionally pick up shiny objects because they believe the birds find them attractive, while it goes unnoticed when magpies interact with less eye-catching items. The folklore may therefore result from observation bias and cultural inflation of orally transmitted episodic events.

Comparative studies of primate personality offer informative insights into the evolutionary origins of personality structure in primate species. Primate personality research has, however, focused on a limited number of species. We investigated personality in three relatively understudied species: Sulawesi black crested macaques (Macaca nigra), Barbary macaques (Macaca sylvanus), and common squirrel monkeys (Saimiri sciureus). We sent a 38-item questionnaire to all European zoological institutions holding the study species and keepers were required to rate individuals on all items. Assessments achieved good levels of interrater reliability. Principal components analysis (PCA) revealed Sociability and Dominance personality dimensions in all study species, an Emotionality dimension in both M. nigra and M. sylvanus, a Cautiousness dimension in S. sciureus, and a Human–Animal Sociability dimension in M. sylvanus. Sociability and Dominance dimensions were shown to have good construct validity, as assessed through appropriate relationships with sex and age and correlations with behavioral measures. The Sociability, Dominance, Emotionality, and Cautiousness dimensions were comparable with analogous dimensions in other primate species but aggressive-type traits did not load onto the Dominance dimension in the two Macaca spp. We suggest that this may be attributed to their more tolerant social systems compared to those of other primate species. The Human–Animal Sociability dimension could not be compared with other primate studies as, to date, there has been limited investigation of human-directed personality dimensions in captive primates. Our findings suggest that the two Macaca species are more similar to each other, in terms of their personality structure, than either is to S. sciureus, which suggests phylogenetic similarity is an important predictor of personality. However, further comparative analysis of a wider range of primate species is needed to inform theories regarding the evolution of primate personality structure.

Humans can spontaneously create rules that allow them to efficiently generalize what they have learned to novel situations. An enduring question is whether rule-based generalization is uniquely human or whether other animals can also abstract rules and apply them to novel situations. In recent years, there have been a number of high-profile claims that animals such as rats can learn rules. Most of those claims are quite weak because it is possible to demonstrate that simple associative systems (which do not learn rules) can account for the behavior in those tasks. Using a procedure that allows us to clearly distinguish feature-based from rule-based generalization (the Shanks–Darby procedure), we demonstrate that adult humans show rule-based generalization in this task, while generalization in rats and pigeons was based on featural overlap between stimuli. In brief, when learning that a stimulus made of two components (“AB”) predicts a different outcome than its elements (“A” and “B”), people spontaneously abstract an opposites rule and apply it to new stimuli (e.g. knowing that “C” and “D” predict one outcome, they will predict that “CD” predicts the opposite outcome). Rats and pigeons show the reverse behavior—they generalize what they have learned, but on the basis of similarity (e.g. “CD” is similar to “C” and “D”, so the same outcome is predicted for the compound stimulus as for the components). Genuinely rule-based behavior is observed in humans, but not in rats and pigeons, in the current procedure.

Third party punishment can be evolutionarily stable if there is heterogeneity in the cost of punishment or if punishers receive a reputational benefit from their actions. A dominant position might allow some individuals to punish at a lower cost than others and by doing so access these reputational benefits. Three vignette-based studies measured participants' judgements of a third party punisher in comparison to those exhibiting other aggressive/dominant behaviours (Study 1), when there was variation in the success of punishment (Study 2), and variation in the status of the punisher and the type of punishment used (Study 3). Third party punishers were judged to be more likeable than (but equally dominant as) those who engaged in other types of dominant behaviour (Study 1), were judged to be equally likeable and dominant whether their intervention succeeded or failed (Study 2), and participants believed that only a dominant punisher could intervene successfully (regardless of whether punishment was violent or non-violent) and that subordinate punishers would face a higher risk of retaliation (Study 3). The results suggest that dominance can dramatically reduce the cost of punishment, and that while individuals can gain a great deal of reputational benefit from engaging in third party punishment, these benefits are only open to dominant individuals. Taking the status of punishers into account may therefore help explain the evolution of third party punishment.

Pigeons were trained to discriminate photographs of cat faces from dog faces. They were then presented with test stimuli involving high- and low-pass spatial filtering. Discrimination was maintained with both types of filtered stimuli, though it was increasingly impaired the more information was filtered out, and high-pass filtering impaired discrimination more than low-pass filtering. The pigeons were then exposed to hybrid stimuli in which high-pass filtered dog faces were combined with low-pass filtered cat faces, and vice versa. Response to hybrid stimuli was determined more by the low spatial frequency content than by the high frequency content, whereas humans viewing the same stimuli at corresponding viewing distance respond more strongly to the high-frequency content. These results are unexpected given that, compared with humans, pigeons’ behavior tends to be controlled by the local details of visual stimuli rather than their global appearance.

How can animals learn the prey densities that are available in an environment that changes
unpredictably from day to day, and how much effort should they devote to doing so, rather than
exploiting what they already know?. Using a two-armed bandit situation, we simulated several
processes that might explain the trade-off between exploring and exploiting. They included an
optimising model, dynamic backward sampling; a dynamic version of the matching law; the Rescorla-
Wagner theory; a neural network model; and an ε-greedy and a rule-of-thumb model, both derived
from the study of reinforcement learning in artificial intelligence. Under conditions like those used in
published studies of birds' performance under two-armed bandit conditions, all models usually
identified the more profitable source of reward, and did so more quickly when the differential of
reward probabilities was greater. Only the dynamic programming model switched from exploring to
exploiting more quickly when available time in the situation was less. If sessions of equal length were
presented in blocks, a session-length effect could be induced in some of the models by allowing
motivational, but not memory, carry-over from one session to the next. The neural network and rule of
thumb models were the most successful overall.

Associations between the sun exposure and sun protective behaviours of adolescents and their friends were examined along with the role played by authoritative parenting and other family and peer socialization factors. Four hundred and two adolescents (198 males, 204 females) participated in the research. It was found that these adolescents and their friends shared similar sun exposure and sun protective behaviours and had similar parenting backgrounds. Parental authoritativeness was positively associated with the use of sun protection, even after the effects of other familial and peer variables were controlled, but not with the time spent sunbathing which was associated with friends’ behaviours. The theoretical and practical implications of these findings are discussed.

Predators are able to identify fine characteristic features of prey and use them to maximise the profitability of foraging. Oystercatchers Haematopus ostralegus select thin-shelled mussels Mytilus edulis to hammer through because they are easier to crack than thick-shelled mussels. But mussel shells are composite structures, so we need to ask what it is about these thin-shelled mussels that make them vulnerable. Here we show that the mussels damaged by Oystercatchers were mainly distinguished by having a significantly thinner prismatic layer than undamaged mussels. Regression analysis indicated that the Oystercatchers' shell selection was independently influenced by the thickness of the prismatic and nacreous layers, but the coefficient for the thickness of the prismatic layer was almost one and a half times that for the nacreous layer. Thus the thickness of the prismatic layer largely determines the vulnerability of the mussel shells. Oystercatchers were more likely to attack mussels by the right valve than the left, and this tendency was accentuated in larger mussels and those with a thicker nacreous layer. © 2011 Elsevier B.V.

The effects of picture manipulations on humans’ and pigeons’ performance were examined in a go/no-go discrimination of two perceptually similar categories, cat and dog faces. Four types of manipulation were used to modify the images. Mosaicization and scrambling were used to produce degraded versions of the training stimuli, whilst morphing and cell exchange were used to manipulate the relative contribution of positive and negative training stimuli to test stimuli. Mosaicization mainly removes information at high spatial frequencies, whereas scrambling removes information at low spatial frequencies to a greater degree. Morphing leads to complex transformations of the stimuli that are not concentrated at any particular spatial frequency band. Cell exchange preserves high spatial frequency details, but sometimes moves them into the “wrong” stimulus. The four manipulations also introduce high-frequency noise to differing degrees. Responses to test stimuli indicated that high and low spatial frequency information were both sufficient but not necessary to maintain discrimination performance in both species, but there were also species differences in relative sensitivity to higher and lower spatial frequency information.

Previous laboratory studies on social learning suggest that some animals can learn more readily if they first observe a conspecific demonstrator perform the task unsuccessfully and so fail to obtain a food reward than if they observe a successful demonstrator that obtains the food. This effect may indicate a difference in how easily animals are able to associate different outcomes with the conspecific or could simply be the result of having food present in only some of the demonstrations. To investigate we tested a scatter-hoarding mammal, the eastern grey squirrel, on its ability to learn to choose between two pots of food after watching a conspecific remove a nut from one of them on every trial. Squirrels that were rewarded for choosing the opposite pot to the conspecific chose correctly more frequently than squirrels rewarded for choosing the same pot (a feature-negative effect). Another group of squirrels was tested on their ability to choose between the two pots when the rewarded option was indicated by a piece of card. This time, squirrels showed no significant difference in their ability to learn to choose the same or the opposite pot. The results add to anecdotal reports that grey squirrels can learn by observing a conspecific and suggest that even when all subjects are provided with demonstrations with the same content, not all learning occurs equally. Prior experience or expectations of the association between a cue (a conspecific) and food influences what can be learned through observation whilst previously unfamiliar cues (the card) can be associated more readily with any outcome.

Pigeons, gray squirrels and undergraduates learned discrimination tasks involving multiple mutually redundant dimensions. There were two sets of experiments. Within each set, stimuli and procedures were as closely similar for the different species as possible, but they differed sharply between sets. First, pigeons and undergraduates learned conditional discriminations between stimuli composed of three spatially separated dimensions, after first being trained to discriminate the individual elements of the stimuli. They were then tested with stimuli in which one of the three dimensions took an anomalous value. The majority of both species categorized test stimuli by their overall similarity to training stimuli, but some individuals of both species categorized them according to a single dimension. Secondly, squirrels, pigeons and undergraduates learned go/no-go discriminations using multiple simultaneous presentations of stimuli composed of three spatially integrated, highly salient dimensions. In tests, the tendency to categorize stimuli including anomalous dimension values unidimensionally was higher than in the first set of experiments and did not differ significantly between species. We conclude that unidimensional categorization of multidimensional stimuli is not diagnostic for analytic cognitive processing, and that any differences in behavior between humans and pigeons in such tasks are not due to special features of avian visual cognition.

Pigeons and undergraduates learned conditional discriminations involving multiple spatially separated stimulus dimensions. Under some conditions the dimensions were made available sequentially. In three experiments the dimensions were all perfectly valid predictors of the response that would be reinforced and mutually redundant; in two others they varied in validity. In tests with stimuli where one of the three dimensions took an anomalous value, most but not all individuals of both species categorized them in terms of single dimensions. When information was delivered as a function of the passage of time, some students but no pigeons waited for the most useful information, especially when the cues differed in objective validity. When the subjects could control information delivery, both species obtained information selectively. When cue validities varied, almost all students tended to choose the most valid cues, and when all cues were valid, some chose the cues by which they classified test stimuli. Only a few pigeons chose the most useful information in either situation. Despite their tendency to unidimensional categorization, the pigeons showed no evidence of rule-governed behavior, but students followed a simple Take the Best rule.

Pigeons, gray squirrels and undergraduates learned discrimination tasks involving multiple mutually redundant dimensions. There were two sets of experiments. Within each set, stimuli and procedures were as closely similar for the different species as possible, but they differed sharply between sets. First, pigeons and undergraduates learned conditional discriminations between stimuli composed of three spatially separated dimensions, after first being trained to discriminate the individual elements of the stimuli. They were then tested with stimuli in which one of the three dimensions took an anomalous value. The majority of both species categorized test stimuli by their overall similarity to training stimuli, but some individuals of both species categorized them according to a single dimension. Secondly, squirrels, pigeons and undergraduates learned go/no-go discriminations using multiple simultaneous presentations of stimuli composed of three spatially integrated, highly salient dimensions. In tests, the tendency to categorize stimuli including anomalous dimension values unidimensionally was higher than in the first set of experiments and did not differ significantly between species. We conclude that unidimensional categorization of multidimensional stimuli is not diagnostic for analytic cognitive processing, and that any differences in behavior between humans and pigeons in such tasks are not due to special features of avian visual cognition.

Pigeons and undergraduates learned conditional discriminations involving multiple spatially separated stimulus dimensions. Under some conditions the dimensions were made available sequentially. In three experiments the dimensions were all perfectly valid predictors of the response that would be reinforced and mutually redundant; in two others they varied in validity. In tests with stimuli where one of the three dimensions took an anomalous value, most but not all individuals of both species categorized them in terms of single dimensions. When information was delivered as a function of the passage of time, some students but no pigeons waited for the most useful information, especially when the cues differed in objective validity. When the subjects could control information delivery, both species obtained information selectively. When cue validities varied, almost all students tended to choose the most valid cues, and when all cues were valid, some chose the cues by which they classified test stimuli. Only a few pigeons chose the most useful information in either situation. Despite their tendency to unidimensional categorization, the pigeons showed no evidence of rule-governed behavior, but students followed a simple Take the Best rule.

Behavioural observations are vital to furthering our knowledge of species’ ecology. Determining a method for formalising the length of behavioural observation time (coined Behaviour Discovery Curve) is practical for both reducing disturbance to the animals observed and limiting costs to the researcher. This paper suggests a method of calculating behaviour discovery curves, which allows researchers to estimate the optimal amount of data to collect when establishing an ethogram. The curve is fitted to a logarithmic model that predicts the rate of new behaviours that will be observed in any given length of observation time. To illustrate the methods, 31 captive red pandas (Ailurus fulgens fulgens) were observed for 30 h each and a behaviour discovery curve was estimated for each animal based on the rate at which new behaviours were observed. We demonstrate how to use the curve in the evaluation of an ethogram, whilst also providing an indication of how many more behaviours would be observed in a specified longer observation period. This is an important consideration in the creation of any ethogram, since there are currently no standard methodologies for establishing ethograms, and no guidelines on how much data is ‘sufficient’ for determining a species’ behavioural repertoire. The curve does not allow an estimate of the total size of the behavioural repertoire, but does allow a systematic analysis of the likely costs and benefits of further observation. We also suggest a method for quantifying the degree of idiosyncrasy of a population.

This review focuses on the success and survivorship of captive-born versus wild-caught
carnivores used in reintroductions. Previous reviews have suggested that reintroduction
projects using captive-born animals are less likely to be successful than projects translocating
wild-caught animals. The purpose of this paper is to examine this statistically and
investigate how captivity may affect the survival of reintroduced carnivores. We examined
results published in previous reviews, and found evidence to support that reintroduction
projects using wild-caught animals are significantly more likely to succeed than projects
using captive-born animals. We further compiled our own review of 45 case studies in carnivore
reintroduction projects (in 17 species across 5 families) to investigate survival rates
rather than overall project ‘success’. We found that (1) wild-caught carnivores are significantly
more likely to survive than captive-born carnivores in reintroductions; (2) that
humans were the direct cause of death in over 50% of all fatalities and (3) that reintroduced
captive-born carnivores are particularly susceptible to starvation, unsuccessful predator/
competitor avoidance and disease.

Farm animals are confronted with major changes in their environment as they go through different phases of the production system. Examples include introduction to a new housing system, provision of a new type of feed, mixing with unfamiliar conspecifics or being exposed to new human handlers. Learning processes that reduce uncertainty in such situations are likely to be very important both for animal welfare and for performance. The aim of this paper is to describe, from the animal's point of view, situations typical of learning in farm animal husbandry and to provide a framework for assessing the significance of learning processes for farm animal husbandry and welfare. The literature reviewed covers experimental studies into the learning abilities of ruminants, pigs and poultry as well as evidence stemming from applied studies showing problems farm animals may face in situations of change. We argue that knowledge of species-specific learning abilities may help in the design of housing systems and the establishment of management routines that facilitate learning by the animals. Having searched the literature, we conclude that there is a lack of studies focusing on the initial phase after the introduction of farm animals into a new housing system and on the way they learn to use new housing equipment. Moreover, we suggest that studies into: (a) learning of farm animals during transport and in the slaughterhouse, (b) their motivation to explore the environment and (c) the development of enrichment tasks taking into account their learning abilities may provide solutions to some animal welfare problems. © 2007 Elsevier B.V. All rights reserved.

Insects, birds, and mammals have been shown capable of encoding spatial information in memory using multiple strategies or frames of reference simultaneously. These strategies include orientation to a goal-specific cue or beacon, to the position of the goal in an array of local landmarks, or to its position in the array of distant landmarks, also known as the global frame of reference. From previous experiments, it appears that birds and mammals that scatter hoard rely primarily on a global frame of reference, but this generalization depends on evidence from only a few species. Here we examined spatial memory in a previously unstudied scatter hoarder, the southern flying squirrel. We dissociated the relative weighting of three potential spatial strategies (beacon, global, or relative array strategy) with three probe tests: transposition of beacon and the rotation or the expansion of the array. The squirrels' choices were consistent with a spatial averaging strategy, where they chose the location dictated by at least two of the three strategies, rather than using a single preferred frame of reference. This adaptive and flexible heuristic has not been previously described in animal orientation studies, yet it may be a common solution to the universal problem of encoding and recalling spatial locations in an ephemeral physical landscape. © 2006 Springer-Verlag.

The cultural norms of traditional societies encourage behavior that is consistent with maximizing reproductive success but those of modern post-demographic transition societies do not. Newson et al (2005) proposed that this might be because interaction between kin is relatively less frequent in modern social networks. Assuming that people's evaluations of reproductive decisions are influenced by a desire to increase their inclusive fitness, they will be inclined to prefer their kin to make fitness-enhancing choices. Such a preference will encourage the emergence of pronatal cultural norms if social networks are dense with kin. Less pronatal norms will emerge if contact between kin makes up a small proportion of social interactions. This article reports evidence based on role-play studies that supports the assumption of the kin influence hypothesis that evaluations of reproductive decisions are influenced by a desire to increase inclusive fitness. It also presents a cultural evolutionary model demonstrating the long-term effect of declining kin interaction if people are more likely to encourage fitness-enhancing choices when interacting with their kin than with nonrelatives. © 2007 Elsevier Inc. All rights reserved.

Our response amplifies our case that money is best seen as both a drug and a tool. Some commentators challenge our core assumptions: in this response we, therefore, explain in more detail why we assume that money is an exceptionally strong motivator, and that a biological explanation of money motivation is required. We also provide evidence to support those assumptions. Other commentators criticise our use of the drug metaphor, particularly arguing that it is empirically empty; and in our response we seek to show how it can be submitted to test - aided by, some commentaries which suggest such tests. In addition, we explain, with evidence, why we do not think that the notion of money as a generalised conditioned reinforcer provides a satisfactory alternative to the tool/drug account. The largest group of commentaries suggests alternative instincts on which the drug-like effects of money might be based, other than the reciprocation and play instincts we propose; in our response, we explain why we still prefer our original proposals, but we accept that alternative or additional instincts may indeed underlie money motivation. A final group of commentaries carries the argument further, suggesting extensions to the tool/drug model, in ways with which we are broadly in sympathy. The purpose of the tool and drug metaphors is to encourage reflection on the biological origins of money motivation, and to that extent at least we believe that they have succeeded.

It is widely agreed that all animals are entitled to some degree of welfare consideration, but that some are entitled to more consideration than others. However, the basis for singling out some animals for special consideration often seems to be mostly a matter of degree of similarity to, or association with, humans. A more reasonable criterion would involve the extent of suffering caused by given events. Two variables that seem likely to be very important in the extent of suffering are the capacity to anticipate and the capacity to recall. Everyday experience tells us that human suffering can be hugely amplified by either anticipation or recall of painful or distressing events. In the past, psychologists have tended to take the view that both these processes depend on the possession of language, and were therefore irrelevant to species other than humans. But comparative psychologists are increasingly making use of concepts from human cognition, including both memory and anticipation, to explain animals' responses to both past and future events. These processes are invoked to explain the behaviour of a wide range of vertebrate species. Recent work on primate cognition indicates that more elaborate forms of representation may be possible in the great apes. Such evidence should be used as the basis for deciding whether to give special welfare consideration to certain species which have special cognitive capacities - or indeed enhanced welfare consideration to a wider range of species, if their cognitive capacities are found to be more sophisticated than is generally assumed.

The aim of this study is to investigate the understanding of wealth, poverty, inequality and unemployment in South African Black (African) children aged 7, 9, 11 and 14 drawn from a rural, an urban and a semi-urban setting. Two hundred and twenty-five children (80 rural, 60 urban and 85 semi-urban) were interviewed individually in Setswana, their mother tongue. The urban children were living in a township in Pretoria, the semi-urban and the rural in the North West Province. The results show that the particulars of the children's knowledge about wealth, poverty, inequality and unemployment were influenced by their social environment. However, in line with previous studies, the results show that the children's capacity to make inferences and integrate information about these concepts is more influenced by age than by their social milieu.

Eight pigeons were trained on a conditional discrimination using red and green saturated and desaturated fields, and red and green saturated and desaturated vertical and horizontal black-on-colour gratings. The pigeons learned to discriminate the stimuli on the basis of colour, to a high level of accuracy, regardless of saturation or the presence of gratings. The pigeons were then repeatedly exposed to stimuli in which colour and grating orientation were correlated, following which they were tested for the presence of the McCollough orientation-contingent colour after-effect, using black-on-white vertical and horizontal gratings. Six of the birds showed convincing evidence of the presence of the McCollough effect, and the effect was significant across all birds. These findings support those of Roberts (1984), using a substantially different methodology. The six birds showing the McCollough effect were then tested for the persistence of the effect at delays of 24 to 96 h. Four of the birds showed evidence of the McCollough effect at least 24 h after the induction procedure. Three of these birds were also tested to investigate the spatial frequency selectivity of the effect. The results suggest a narrow tuning of the McCollough effect in pigeons of less than 0.36 log units. Copyright (C) 1999 Elsevier Science B.V.

Oystercatchers Haematopus ostralegus periodically pause while handling mussels Mytilus edulis to make visual scans. This paper presents evidence that scanning is associated with the high incidence of intra-specific food stealing among mussel-eating Oystercatchers. Scanning increased in frequency as bird density - and the risk of being attacked for mussels - increased and the duration of attacks decreased. Additionally, among a sample of individually marked adults, the aggressive dominant birds spent half as much time scanning as the less aggressive subdominants and were also less likely to be attacked. Whereas detecting an attack made no difference to the success with which the dominants defended their mussels, subdominants increased their chances of retaining the mussel if they detected and carried the mussel away from the approaching attacker. The extra time which the less aggressive birds spent in vigilance seems best understood as a tactic for reducing food loss to kleptoparasites.

In three experiments, pigeons were exposed to a discriminated antoshaping procedure in which categories of moving stimuli, presented on videotape, were differentially associated with reinforcement. All stimuli depicted pigeons making denned responses. In Experiment 1, one category consisted of several different scenes of pecking and the other consisted of scenes of walking, flying, head movements, or standing still. Four of the 4 birds for which pecking scenes were positive stimuli discriminated successfully, whereas only 1 of the 4 for which pecking was the negative category did so. In the pecking-positive group, there were differences between the pecking rates in the presence of the four negative actions, and these differences were consistent across subjects. In Experiment 2, only the categories of walking and pecking were used; some but not all birds learned this discrimination, whichever category was positive, and these birds showed some transfer to new stimuli in which the same movements were represented only by a small number of point lights (Johansson's "biological motion" displays). In Experiment 3, discriminations between pecking and walking movement categories using point-light displays were trained. Four of the 8 birds discriminated successfully, but transfer to fully detailed displays could not be demonstrated. Pseudoconcept control groups, in which scenes from the same categories of motion were used in both the positive and negative stimulus sets, were used in Experiments 1 and 3. None of the 8 pigeons trained under these conditions showed discriminative responding. The results suggest that pigeons can respond differentially to moving stimuli on the basis of movement cues alone.

When juvenile oystercatchers, Haematopus ostralegus, first arrived on the wintering grounds in August and September, they regularly stole mussels, Mytilus edulis, from other, mainly older, oystercatchers. By October, however, juveniles stole far fewer mussels and found almost all their mussels independently for themselves on the mussel bed. Although stealing a mussel was always less profitable than taking a mussel from the mussel bed, a simple rate-maximizing optimality model showed that, in August and September, juveniles increased both their net and gross rates of energy intake by stealing because they were rather inefficient at foraging for themselves. By October, their greater efficiency at finding good quality mussels, combined with the increased resistance of potential victims to kleptoparasitic attacks, resulted in higher intake rates if juveniles stopped stealing mussels and took mussels only from the mussel bed. Copyright 1998 the Association for the Study of Animal Behaviour Copyright 1998 the Association for the Study of Animal Behaviour.

This paper presents an economic-psychological analysis of the concept of pride. Although it was one of the traditional Seven Deadly Sins, pride has been regarded by psychology as a positive rather than a negative quality. It is usually viewed as an emotion elicited by one's own or others' achievement and associated with self-esteem and positive self-image. However, it is necessary to distinguish 'proper pride', associated with genuine achievements, and 'false pride' (vanity or conceit) which can be maladaptive or even pathological. Familiar social psychological processes such as self-serving bias are likely to give rise to false pride, which is in turn likely to lead to erroneous or apparently irrational decisions. It is at this point that pride has implications for economic behaviour. We examine the role of pride in three economic situations: in work, where pride may lead to a preference for doing high quality work; in relation to social security benefits, where pride may depress take-up; and in negotiations, where pride may lead to an 'irrationally' hard negotiating position. We argue that in all cases pride is involved because economic decisions are not taken in isolation from one another, but are linked together by the selfhood of the people who take them. Although pride can lead to decisions that are maladaptive from any perspective, in many cases it functions to ensure that people take decisions that are in their long-term interests, even when in the short term they would appear irrational. We conclude that economic analysis needs to take more account of the selfhood of economic agents, while the psychology of pride needs to take more account of economic behaviour.

The Overjustification effect demonstrates that payment for an activity can have negative after-effects on performance. The implications of this effect for work motivation theory are discussed and it is argued that the overjustification effect is best regarded as being driven by a single source of work motivation (motivation to control). This is contrasted with theories that either advocate two sources of work motivation (intrinsic and extrinsic motivation) or that disregard work motivation in their analysis of the overjustification effect. An economic analysis of the many different instances of people's paid and unpaid activities shows how a motivation to control one's environment induces people to dislike activities that are paid. A distinction is made between payment in general, which is thought to make people regard their activity as one of work and monetary payment, which is thought to make people feel relatively deprived of the outcomes of their work. © 1996 JAI Press, Inc. All rights of reproduction in any form reserved.

Four species of shags and cormorants were observed while diving for food in estuaries and coastal waters in southwest England and the South Island of New Zealand. Times spent on the surface and under water were recorded. The correlations between dive and surface times were examined between and within bouts of dives. All species showed a positive correlation between the mean dive time and the mean surface time for the bout. Analysis of within-bout correlations, however, showed different patterns between species. For the Shag Phalacrocorax aristotelis, there was a positive relationship within bouts between dive time and the preceding surface time, and correlations between dive time and the succeeding surface time were due only to the autocorrelation of surface times. This anticipatory breathing pattern was predicted by an optimal breathing model proposed by D. L. Kramer. For the Little Shag Phalacrocorax melanoleucus, dive times were significantly correlated within bouts with the following surface time, but correlations with the succeeding surface time were due only to the autocorrelation of surface times. This implies that breathing in this species is reactive rather than anticipatory. The Cormorant Phalacrocorax carbo and the Pied Shag Phalacrocorax varius showed independent within-bout correlations with both preceding and succeeding surface times, implying both anticipatory and reactive breathing. The within-bout dependence of dive time on surface times was weak in all species, suggesting that oxygen is stored from one dive to another to some extent.

The diet and feeding behaviour of Cercopithecus preussi in montane forest on Kilum Mountain, Cameroon, was studied over a period of 15 months and compared with that of Cercopithecus mitis observed over a similar period in montane forest on the Zomba Plateau, Malawi. Cercopithecus preussi was found to eat fruit with a similar frequency to C. mitis, but to eat mature tree leaves less often. When the frequency of total green plant intake was compared, however, C. preussi ate this category more often than C. mitis. This may reflect the raised foliar protein levels at Kilum, a longer rainy season increasing the availability of preferred food items and the greater terrestriality of C. preussi, bringing it into contact with more herb leaf blades. Both C. preussi and C. mitis eat the blades of mature tree leaves relatively rarely, preferring leaf shoots (C. preussi) and leaf petioles (C. mitis).

Newly hatched chicks (Gallus gallus) were imprinted on a display consisting of two rod pieces that moved above and below a central occluder. On test trials, the chicks approached a complete rod in preference to two rod pieces. This finding, supported by those from control coditions, suggests that chicks, soon after hatching, perceive object unity. The results are compared with those from human infants. © 1996 Ablex Publishing Corporation.

Predictions of microeconomic theory were investigated in four experiments in which respondents rated the utility of consumer goods. Experiment 1 found that ratings of marginal utility depended on the price but not on the frequency of consumption of the goods. Experiment 2 suggested respondents rate total and marginal utility independently. In Experiment 3, goods with higher perceived elasticity of demand were rated of less value, while a positive correlation between consumer's surplus and average value of goods was found in Experiment 4. These findings were all consistent with microeconomic theory. © 1995.

A postal survey study of factors correlated with consumer debt investigated several psychological variables which have been suggested as causes or effects of debt. The survey was conducted with the help of a public utility company, and questionnaires were sent to three groups with different debt histories over the preceding two years: Non-Debtors (no debt to the company), Mild Debtors (late payment to the company), and Serious Debtors (sued for debt recovery by the company). Economic and demographic factors predicted debt category well, supporting previous results. Further variance between groups was accounted for by people's money management skills and facilities, by measures of their time horizons, and by aspects of their consumer behaviour. Non-debtors had more money management facilities (e.g. bank accounts) than debtors, and rated their abilities at money management more highly. Debtors had shorter time horizons than non-debtors. Debtors were more likely to buy cigarettes and Christmas presents for children than non-debtors. No group differences were found for attitudes to debt or locus of control. There were significant group differences for measures of economic socialization, social comparisons, use of credit, and other aspects of consumer behaviour, but these differences were not independently significant on multivariate analysis. Conclusions must be qualified because of low return rates, but the results suggest that a complex of psychological and behavioural variables affect debt and are affected by it. It is argued that these variables are linked to the psychology of poverty. © 1995.

Levels of debt and attitudes towards debt were investigated in a sample of undergraduate students. Students were found to be a relatively low-income, high-debt group with relatively tolerant attitudes towards debt. Some of the variables that have been found to be associated with debt in general public samples were also found to have significant effects in the student group: these included religion, age, number of credit cards used, and more tolerant attitudes towards debt. In addition, men were more likely to be in debt than women. Variables correlated with tolerant attitudes towards debt included age, some kinds of expenditure, religion, and external locus of control. A pseudo-longitudinal design was used to examine the relationship between attitudes and debt: cohort (year of study) was taken as a proxy for time. Higher levels of debt, and greater tolerance of debt, were found in students who had been at university longer. The increase in debt occurred earlier in students' careers than the increase in tolerance towards debt. The results are interpreted in terms of a life cycle theory of economic behaviour, and a behavioural theory of attitude change. Students come from relatively prosperous socioeconomic groups but have low incomes which they perceive as temporary; to sustain their expected life style, they have to accept some level of debt. Their attitudes then adjust towards tolerance of debt so as to ensure consistency. © 1995.

Four experiments investigated the discrimination of images of conspecifics by pigeons; in Experiment 1, chickens were also used as subjects, and images of allospecifics were also used as discriminative stimuli. In Experiment 1, chickens were successfully trained to discriminate slides of pigeons, pictures of one bird being positive stimuli and pictures of another bird being negative; and pigeons were similarly trained to discriminate slides of chickens. However, an attempt to train pigeons to discriminate slides of pigeons only succeeded with one bird out of six. Pigeons were slower to learn chicken slides, and chickens were slower to learn pigeon slides, than chickens were to learn chicken slides in a previous experiment. In Experiment 2, a dishabituation technique was used to demonstrate that pigeons readily discriminate individual live pigeons. In Experiment 3, an attempt was made to test habituation to life-size moving video images of pigeons, but these images did not elicit any natural social responses from the subject pigeons. In Experiment 4 pigeons were trained in a discrimination in which the objects to be discriminated were two different stuffed pigeons. No pigeon learned this discrimination. The experiments give some evidence that chickens are better at discriminating images of individuals than pigeons. No single feature seems to be sufficient for pigeons to discriminate between conspecifics, but the combination of features that is required remains unknown. © 1994.

Mature leaves from two Afro‐montane forests in widely separated parts of Africa were compared for protein and acid detergent fibre content, major factors in their potential as food items for members of Cercopithecus spp. which inhabit both forests. Leaves from Kilum Mountain Forest in Cameroon, which grows on volcanic soils, had a much higher protein content than leaves from the Zomba Plateau in Malawi, where the soils are derived from syenite and granite rocks. Fibre content, however, was similar in both forests. Members of the same species on different sites also showed the same pattern, indicating that it was not the result of floral divergence. On a comparé les feuilles à maturityé de deux forêts afromontagnardes dans deux parties très éloignées d'Afrique pour leur contenu en protéines et en fibres détersives acides, facteurs majeurs pour leur possibilityé de servir de nourriture aux membres des Cercopithecus spp. qui habitent les deux forêts. Les feuilles de la Forêt de Montagne de Kilum, au Cameroun, qui pousse sur un sol volcanique, ont un contenu protéinique bien plus élevé que celles du Plateau de Zomba, au Malawi, où les sols sont à base de syénite et de roches granitiques. Cependant, le contenu en fibres est le même dans les deux forêts. Les mêmbres des memes espèces présentaient aussi le même schéma aux différentes places, montrant par lá que ce n'était pas le résultat d'une divergence florale. Copyright © 1994, Wiley Blackwell. All rights reserved

A series of experiments were performed to investigate how motion sequences provide information about the intentional structure of moving figures or actors. Observers had to detect simulations of biologically meaningful motion within a set of moving letters. In the first two experiments a factorial design was used, with type of instruction as a between-subject factor and six movement parameters (number of items, speed and directness of target and distractors, and 'relentlessness' of target movement) as within-subject factor; in the final two experiments, the visibility of the goal towards which the target moved and the use of a tracking movement to distinguish the target were varied. In such displays search time increases with increasing number of stimuli. It was found that (a) the more direct the motion, the more likely it was to be interpreted as intentional; (b) intentional motion was much easier to detect when the target moved faster than the distractors than when it moved more slowly; (c) recognition of intentionality was impaired but not abolished if the goal towards which the target was moving was invisible; and (d) participants did not report intentional movement when the target was distinguished by brightness rather than the manner in which it moved. We argue that the perception of intentionality is strongly related to observers' use of conceptual knowledge, which in turn is activated by particular combinations of features. This supports a process model, in which intentionality is seen as the result of a conceptual integration of objective visual features.

In this paper we argue that current research into economic socialisation is unsatisfactory for two main reasons. Most researchers have tended to regard the meaning of the term 'economic' as static and given and so have taken an adult-centred view of the child's world and investigated only those domains which are obviously economic (working, spending, borrowing, saving etc.). Secondly, researchers have concentrated almost exclusively on the question of cognitive development and so have asked 'how do children come to understand the economic world of grown-ups' and not 'how do children solve the economic problems they are faced with'. We propose that researchers should be more concerned with the real economic world of childhood and we describe a few investigations that we have done in the style we favour. We conclude by discussing the implications of this approach for the future of economic psychology. © 1993.

Three experiments were carried out to investigate people's concept of money. In the first experiment, subjects were asked to rate items for their typicality as money, and subsequently to say, as quickly as possible, whether or not those items were 'a kind of money'. Subjects were quicker to categorize the more typical instances. In the second experiment, subjects were asked to rate the similarities between pairs of instances of the money concept. The mean ratings were well described by a single-link cluster analysis whose structure was dominated by the factor of typicality. These two experiments were both carried out in England. The third experiment was conducted in both England and the Netherlands, and was preceded by a postal questionnaire aiming to identify items which were widely agreed to be instances of money. It combined the manipulations of the first two experiments, and the same patterns of categorization times and similarity ratings were found. In addition, multidimensional scaling showed that typical value is an important dimension in determining the similarities between kinds of money. There were interpretable differences in the similarity ratings between the English and Dutch samples. The three experiments show that money is a typical 'polymorphous concept', that is, a concept whose definition and boundaries cannot be specified precisely, but which nonetheless can be used consistently and efficiently. © 1992.

In three experiments, pigeons (domesticated Columba livia) were exposed to concurrent randomratio schedules of reinforcement in a keypecking apparatus, as a simulation of foraging in an environment containing two patches of unknown food density. All reinforcements were given for pecks on a single key, but different patch densities were associated with different key colours, and the colour was changed following pecks to a second key. Patch densities varied from day to day, and no colour reliably signalled the better patch from session to session. In the first experiment, either 256 or 1024 pecks were allowed per session. As predicted by optimal sampling theory, the proportion of the first 256 pecks made in the denser patch, and the number of reinforcements gained during them, were higher in the short than in the long sessions. These results were simulated using principles derived from operant conditioning theory. In the second experiment, the number of different patch densities used was varied between conditions. Birds made fewer patch changes when the density range was more restricted. In the third experiment, the colour cues differentiating patch densities were dropped in one condition, and the birds were less successful at finding the better patch in this condition. These results show that pigeons are sensitive to aspects of a foraging situation that are predicted by optimal sampling theory (e.g. the session length), and also in ways that have not been considered so far (e.g. patch density range). But they also show that cues that are not logically necessary (e.g. patch key colour) may in practice be an essential part of an animal's mechanism for achieving efficient foraging. © 1987.

Unlike many other species, golden hamsters (Mesocricetus auratus) do not compensate for a loss in weight following a brief period of food deprivation: this may be due to their adaptation for a hoarding mode of life. We studied the interaction of hoarding with deprivation and a second challenge to body weight, increasing food costs. Hamsters earned all their food in operant chambers, in which they lived. The cost of food was varied by making it available on several different fixed ratio schedules. Regardless of whether the hoard was taken away each day (experiments 1 and 3) or left intact (experiments 2 and 4), food consumption was virtually constant as cost increased, but hoarding declined sharply. Hoarding was enhanced by a short deprivation period (experiment 3) especially when the subsequent cost of food was low (experiment 4). The results suggest that hamsters do indeed show compensatory behaviour following deprivation, or when the cost of foraging is high, but its form is different from that seen in non-hoarding species. © 1986.

Previous research has shown that response rates on a variable interval (VI) schedule of reinforcement decrease if a brief response-produced signal is given prior to reward. One explanation is that the signal overshadows the response because it is a better predictor of reinforcement. The S-R overshadowing effect does not occur with variable ratio (VR) schedules, however. Tarpy, Lea, and Midgley (1983) explained this fact by suggesting that the signal functions to enhance the salience of the temporal interval offset on the VI schedule (a characteristic not possessed by VR schedules), which then overshadows the response. In this experiment, the salience of the temporal interval was enhanced in another way: signaled or unsignaled reward was provided to rats responding on either a VI or fixed interval (FI) reward schedule. As predicted, rates were lowest for animals receiving signaled reinforcement on an FI schedule and highest for those receiving unsignaled reinforcement on a VI schedule. © 1984 Psychonomic Society, Inc.

Economic psychology is simply the attempt to explore the interconnections between economics and psychology in a systematic way and come up with a coherent interdisciplinary account of the phenomena to be observed at their interface. As an integrated field of study, it does not really exist in the English-speaking world, but it does have quite a long and continuous history on the European continent. Most Americans who have thought about the relation between economics and psychology in recent years have been trying to do one of two things. Either they have been trying to understand economic behavior in terms of principles derived from the psychological study of individuals or else they have been trying to apply economic models to individual behavior. As per economic determinism, individual psychology is a function of the economic situation. As per conspicuous consumption, many goods are consumed simply because they are expensive; their purchase, therefore, signals that the purchaser can afford them, and therefore has social status, position, or power. © 1983, North-Holland Publishing Company

In four studies, subjects were asked whether money was an acceptable gift. In the first study, students stated that they would find it less acceptable to give their mothers a cheque than a gift token or a selected present; and that if they had to send a cheque they would spend more than twice as much on it as on the other sorts of gift. The second study confirmed these results on a larger, non-student sample of young adults, and also showed that it made no difference whether a cheque or cash was specified. In the third study, students were asked about the reasons why they would find it unacceptable to give or receive a cheque as a present. The most important reasons focused on the time and effort that ought to be spent on selecting a present, and the possibility that money sent as a gift might be used for mundane purchases. In the final study, mothers of students were asked about the kinds of presents they would find it acceptable to receive: they indicated that a cheque would be less acceptable than a selected present of a gift token, but they did not expect more to be spent on a cheque than on other gifts. Taken together, these results strongly confirm casual impressions that money is unacceptable as a gift in some contexts, implying both that the element of social exchange is crucially important in gift-giving, and that even in modern societies money is not a universally acceptable medium of exchange. © 1983.

Rats lived in Skinner boxes and pressed levers for all their food. Food was delivered according to fixed-ratio (FR) and variable-interval (VI) schedules, or rats were yoked to other subjects working on DRs. Half of the sessions involved rich schedules (FR-30, VI- 2 min, Yoked-30), the other half lead schedules (FR-75, VI-5, Yoked-75). Each subject was exposed to each condition, in a balanced order, and each schedule was in effect for 3 days. Reinforcements obtained varied significantly between rich and lean schedules of each type, i.e. demand was elastic, but did not vary between schedule types. The price paid (responses per pellet) depended on schedule type as well as severity. Thus the data could not be fitted to a single demand curve, suggesting that demand is a function of specific schedule contingencies, not simply cost factors.

Psychologists working in the operant (Skinnerist) tradition are currently pursuing a rapprochement with economies. This trend arises from the preoccupation of operant psychology with problems like choice, and it involves the study of clinical populations in token economies and also of animal behaviour in laboratory settings. Problems with using animals include those of extrapolating across species, of the absence of a medium of exchange or rational forethought in animal social interaction, and the risk of producing too simple and formal an analysis. But there are compensating advantages, such as investigating fields where experimentation in. the real economy is impossible, securing continuity with disciplines like ecology, and investigating possible mechanisms for "rational" behaviour. Data collected so far do demonstrate continuities between animal and human economic behaviour. © 1981.

Subjects who were asked, in 1976, to estimate the sizes of British coins either under their current names or under their names before decimalization in 1971, gave bigger estimates under the old names. This difference is attributed to the loss of value of the coins since 1971. © 1981.

Six rats lever pressed for food on concurrent fixed‐ratio schedules, in a two‐compartment chamber. In one compartment, mixed diet pellets were delivered on fixed‐ratio schedules of 1, 6, 11, and 16; in the other, either no food was delivered, or sucrose or mixed diet pellets were delivered on fixed‐ratio 8. The number of pellets obtained in the first compartment declined as a function of fixed‐ratio size in that compartment in all three conditions, but the decline was greatest overall with mixed diet pellets concurrently available in the other compartment, and least with no food concurrently available. The result is discussed in terms of economic demand theory, and is consistent with the prediction that elasticity of demand for a commodity (defined in operant terms as the ratio of the proportionate change in number of reinforcements per session to the proportionate change in fixed‐ratio size) is greater the more substitutable for that commodity are any concurrently available commodities. 1977 Society for the Experimental Analysis of Behavior

In each of the two experiments, a group of five rats lived in a complex maze containing four small single‐lever operant chambers. In two of these chambers, food was available on variable‐interval schedules of reinforcement. In Experiment I, nine combinations of variable intervals were used, and the aggregate lever‐pressing rates (by the five rats together) were studied. The log ratio of the rates in the two chambers was linearly related to the log ratio of the reinforcement rates in them; this is an instance of Herrnstein's matching law, as generalized by Baum. Summing over the two food chambers, food consumption decreased, and response output increased, as the time required to earn each pellet increased. In Experiment II, the behavior of individual rats was observed by time‐sampling on selected days, while different variable‐interval schedules were arranged in the two chambers where food was available. Individual lever‐pressing rates for the rats were obtained, and their median bore the same “matching” relationship to the reinforcement rates as the group aggregate in Experiment I. There were differences between the rats in their distribution of time and responses between the two food chambers; these differences were correlated with differences in the proportions of reinforcements the rats obtained from each chamber. 1977 Society for the Experimental Analysis of Behavior

Rats in a two-lever situation were exposed to alternating periods of intermittent reinforcement and extinction. Extinction periods were either unsignalled or were signalled by a response-produced stimulus. The signal was sometimes a stimulus paired with food delivery in the reinforcement periods and sometimes a stimulus that occurred only in extinction periods. Both kinds of signal accelerated extinction relative to the unsignalled condition. When the signal was the stimulus paired with food in reinforcement periods, the rats tended to prefer the lever that gave that signal even though the signal accelerated extinction. There was no comparable effect for the stimulus that occurred only in extinction periods; when this signal was contingent on only one of the two levers, the rats either avoided it (Experiment 3) or were indifferent (Experiment 4). It is concluded that a stimulus can be a "secondary reinforcer" as measured by preference, even though it decreases resistance to extinction; the implications are discussed with reference to formal theories of choice behavior. © 1976.

Pigeons learned to discriminate between 'A's and '2's in eighteen different typefaces. They subsequently showed excellent transfer to twenty two typefaces that they had not previously seen; one pigeon was tested with handwritten letters and responded correctly to them also. Pigeons' responses to 'A's and '2's with parts removed suggested that their performance was controlled by several features, none of which alone could be considered necessary or sufficient. A test in which birds were shown other letters of the alphabet supported this conclusion. It appears that the original discrimination was learned as what Ryle calls a 'polymorphous concept'.

Pigeons were tested in a computer‐controlled two‐key chamber. A standard (nonchanging) schedule of reinforcement was in force on one key, and an adjusting schedule on the other. The schedules were available concurrently after each reinforcement, but after the first peck on either key (the choice peck), the schedule on the other key was made inoperative. The parameter of the adjusting schedule was decreased when the standard schedule was chosen and increased when the adjusting schedule was chosen. The standard schedule was changed only between sessions. Fixed intervals and fixed ratios were used as standard schedules, and intervals and ratios were used as adjusting schedules. When standard and adjusting schedules were of the same type, median parameters on the adjusting key equalled those of the standard schedules, at four values of each standard schedule. For four of five birds, and for the group median, similar curves could be plotted through the indifference points obtained from a standard ratio with an adjusting interval, and from a standard interval with an adjusting ratio. These points showed consistent individual differences, but they could be predicted by assuming that the median time from the choice peck to reinforcement should be the same on both keys. This is equivalent to treating the schedule as a concurrent chain and assuming that Herrnstein's quantitative law of effect applies. 1976 Society for the Experimental Analysis of Behavior

THERE is a simple rule that defines which of the symbols of Fig. 1 fall into group a and which into group B. It can be expressed in thirteen words, but the reader is unlikely to guess it - even if we tell him that the only relevant differences between the patterns are in symmetry, dot colour and dot shape. © 1973 Nature Publishing Group.