Key publications
Chow PKY, Lea SEG, Leaver LA (2016). How practice makes perfect: the role of persistence, flexibility and learning in problem solving efficiency.
Animal Behaviour, 273-283.
Abstract:
How practice makes perfect: the role of persistence, flexibility and learning in problem solving efficiency
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.
Abstract.
Chow PKY, Leaver LA, Wang M, Lea SEG (2015). Serial Reversal Learning in Gray Squirrels: Learning Efficiency as a Function of Learning and Change of Tactics.
JOURNAL OF EXPERIMENTAL PSYCHOLOGY-ANIMAL LEARNING AND COGNITION,
41(4), 343-353.
Author URL.
Hopewell LJ, Leaver LA, Lea SEG, Wills AJ (2010). Grey squirrels (Sciurus carolinensis) show a feature-negative effect specific to social learning.
Anim Cogn,
13(2), 219-227.
Abstract:
Grey squirrels (Sciurus carolinensis) show a feature-negative effect specific to social learning.
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.
Abstract.
Author URL.
Smulders T, Gould K, Leaver LA (2010). Using ecology to guide the study of cognitive and neural mechanisms of different aspects of spatial memory in food-hoarding animals.
Philosophical Transactions of the Royal Society B,
365, 883-900.
Abstract:
Using ecology to guide the study of cognitive and neural mechanisms of different aspects of spatial memory in food-hoarding animals
Understanding the survival value of behaviour does not tell us how the mechanisms that control this
behaviour work. Nevertheless, understanding survival value can guide the study of these mechanisms.
In this paper, we apply this principle to understanding the cognitive mechanisms that
support cache retrieval in scatter-hoarding animals. We believe it is too simplistic to predict that
all scatter-hoarding animals will outperform non-hoarding animals on all tests of spatial memory.
Instead, we argue that we should look at the detailed ecology and natural history of each species.
This understanding of natural history then allows us to make predictions about which aspects of
spatial memory should be better in which species. We use the natural hoarding behaviour of the
three best-studied groups of scatter-hoarding animals to make predictions about three aspects of
their spatial memory: duration, capacity and spatial resolution, and we test these predictions against
the existing literature. Having laid out how ecology and natural history can be used to predict
detailed cognitive abilities, we then suggest using this approach to guide the study of the neural
basis of these abilities. We believe that this complementary approach will reveal aspects of
memory processing that would otherwise be difficult to discover.
Abstract.
Wills AJ, Lea SEG, Leaver LA, Osthaus B, Ryan CME, Suret MB, Bryant CML, Chapman SJA, Millar L (2009). A comparative analysis of the categorization of multidimensional stimuli: I. unidimensional classification does not necessarily imply analytic processing; evidence from pigeons (Columba livia), squirrels (Scurius carolinensis) and humans (Homo sapiens).
Journal of Comparative Psychology,
123(4), 391-405.
Abstract:
A comparative analysis of the categorization of multidimensional stimuli: I. unidimensional classification does not necessarily imply analytic processing; evidence from pigeons (Columba livia), squirrels (Scurius carolinensis) and humans (Homo sapiens)
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.
Abstract.
Hopewell LJ, Leaver LA, Lea SEG (2008). Effects of Competition and Food Availability on Travel Time in Scatter-hoarding Grey Squirrels (Sciurus carolinensis). Behavioral Ecology(19), 1143-1149.
Publications by category
Journal articles
Leaver L, Lea S, Chow P, McLaren I (In Press). Behavioral Flexibility: a review, a model and some exploratory tests. Learning and Behavior
Leaver L, Ford S, Miller C, Yeo M, Fawcett T (In Press). Learning is negatively associated with strength of left/right paw preference in wild grey squirrels (Sciurus carolinensis). Learning and Behavior
Lea SEG, Pothos E, Wills A, Leaver L, Ryan C, Meier C (In Press). Multiple feature use in pigeons’ category discrimination: the influence of stimulus set structure and the salience of stimulus differences. Journal of Experimental Psychology: Animal Learning and Cognition
Leaver L, Wilkinson A (2020). A special issue in honour of Stephen Lea - a true comparative psychologist.
Learn Behav,
48(1), 7-8.
Author URL.
Chow PKY, Leaver LA, Wang M, Lea SEG (2017). Touch screen assays of behavioural flexibility and error characteristics in Eastern grey squirrels (Sciurus carolinensis). Animal Cognition, 20(3), 459-471.
Leaver LA, Jayne K, Lea SEG (2016). Behavioral flexibility versus rules of thumb: how do grey squirrels deal with conflicting risks?. Behavioral Ecology, 28(1), 186-192.
Chow PKY, Lea SEG, Leaver LA (2016). How practice makes perfect: the role of persistence, flexibility and learning in problem solving efficiency.
Animal Behaviour, 273-283.
Abstract:
How practice makes perfect: the role of persistence, flexibility and learning in problem solving efficiency
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.
Abstract.
Jayne K, Lea SEG, Leaver LA (2015). Behavioural responses of Eastern grey squirrels, <i>Sciurus carolinensis</i>, to cues of risk while foraging.
BEHAVIOURAL PROCESSES,
116, 53-61.
Author URL.
Chow PKY, Leaver LA, Wang M, Lea SEG (2015). Serial Reversal Learning in Gray Squirrels: Learning Efficiency as a Function of Learning and Change of Tactics.
JOURNAL OF EXPERIMENTAL PSYCHOLOGY-ANIMAL LEARNING AND COGNITION,
41(4), 343-353.
Author URL.
Farmer HL, Plowman AB, Leaver LA (2011). Role of vocalisations and social housing in breeding in captive howler monkeys (Alouatta caraya).
Applied Animal Behaviour Science,
134(3-4), 177-183.
Abstract:
Role of vocalisations and social housing in breeding in captive howler monkeys (Alouatta caraya)
Over the last 12 years the European captive population of black and gold howler monkeys, Alouatta caraya, has increased at a slow rate and many groups have not produced offspring. This study aims to determine the influence of social organisation of captive groups and both performing and hearing howl vocalisations on reproductive success. Data were extracted from the European Studbook to calculate three variables of female reproductive success per capita, for each year of their reproductively active life (from three years of age). Reproductive success for females was measured as the occurrence of a birth each year, the total number of births per year and the number of successful births per year (offspring surviving to one year of age). Male data were analysed separately, using behavioural observations in addition to studbook data, to determine the effect of daily howling rates on reproductive success (mean number of offspring surviving to one year of age). We found that more offspring were born to and survived (both P
Abstract.
Hopewell LJ, Leaver LA, Lea SEG, Wills AJ (2010). Grey squirrels (Sciurus carolinensis) show a feature-negative effect specific to social learning.
Anim Cogn,
13(2), 219-227.
Abstract:
Grey squirrels (Sciurus carolinensis) show a feature-negative effect specific to social learning.
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.
Abstract.
Author URL.
Smulders T, Gould K, Leaver LA (2010). Using ecology to guide the study of cognitive and neural mechanisms of different aspects of spatial memory in food-hoarding animals.
Philosophical Transactions of the Royal Society B,
365, 883-900.
Abstract:
Using ecology to guide the study of cognitive and neural mechanisms of different aspects of spatial memory in food-hoarding animals
Understanding the survival value of behaviour does not tell us how the mechanisms that control this
behaviour work. Nevertheless, understanding survival value can guide the study of these mechanisms.
In this paper, we apply this principle to understanding the cognitive mechanisms that
support cache retrieval in scatter-hoarding animals. We believe it is too simplistic to predict that
all scatter-hoarding animals will outperform non-hoarding animals on all tests of spatial memory.
Instead, we argue that we should look at the detailed ecology and natural history of each species.
This understanding of natural history then allows us to make predictions about which aspects of
spatial memory should be better in which species. We use the natural hoarding behaviour of the
three best-studied groups of scatter-hoarding animals to make predictions about three aspects of
their spatial memory: duration, capacity and spatial resolution, and we test these predictions against
the existing literature. Having laid out how ecology and natural history can be used to predict
detailed cognitive abilities, we then suggest using this approach to guide the study of the neural
basis of these abilities. We believe that this complementary approach will reveal aspects of
memory processing that would otherwise be difficult to discover.
Abstract.
Wills AJ, Lea SEG, Leaver LA, Osthaus B, Ryan CME, Suret MB, Bryant CML, Chapman SJA, Millar L (2009). A comparative analysis of the categorization of multidimensional stimuli: I. unidimensional classification does not necessarily imply analytic processing; evidence from pigeons (Columba livia), squirrels (Scurius carolinensis) and humans (Homo sapiens).
Journal of Comparative Psychology,
123(4), 391-405.
Abstract:
A comparative analysis of the categorization of multidimensional stimuli: I. unidimensional classification does not necessarily imply analytic processing; evidence from pigeons (Columba livia), squirrels (Scurius carolinensis) and humans (Homo sapiens)
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.
Abstract.
Lea SEG, Wills AJ, Leaver LA, Ryan CME, Bryant CML, Millar L (2009). A comparative analysis of the categorization of multidimensional stimuli: II. Strategic information search in humans (Homo sapiens) but not in pigeons (Columba livia).
Journal of Comparative Psychology,
123(4), 406-420.
Abstract:
A comparative analysis of the categorization of multidimensional stimuli: II. Strategic information search in humans (Homo sapiens) but not in pigeons (Columba livia)
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.
Abstract.
Gilbert-Norton LB, Leaver LA, Shivik JA (2009). The effect of randomly altering the time and location of feeding on the behaviour of captive coyotes (Canis latrans).
APPL ANIM BEHAV SCI,
120(3-4), 179-185.
Abstract:
The effect of randomly altering the time and location of feeding on the behaviour of captive coyotes (Canis latrans)
Captive carnivores appear highly Susceptible to the negative effects of predictable feeding routines. Current research and reviews suggest feeding unpredictably may increase species typical behaviour, but positive results have been limited to a few species. Our objectives were to determine whether randomly altering the time and location of feeding increased species typical behaviour, or affected the temporal distribution of captive coyote (Canis latrans) behaviour. We assigned 12 coyotes individually to either a predictable or an unpredictable (in time and location) feeding condition and measured behaviours in the morning and evening. Overall, mean time spent foraging, travelling, resting or standing was similar in both conditions, but coyotes in the unpredictable condition marked (118 vs. 42: P= 0.01, one-tailed) and howled (81 vs. 24; P= 0.05, one-tailed) significantly more than coyotes in the predictable condition. There were also significant temporal differences (a.m. vs. p.m.) in behaviour between conditions. Specifically, coyotes fed predictably foraged (P = 0.03) and travelled (P = 0.03) more in the morning and rested (P = 0.03) more in the evening, whereas coyotes fed unpredictably howled (62 vs. 19; P = 0.03) and stood (P = 0.05) more in the morning and foraged (P = 0.03) more in the evening. Optimum predictability for captive carnivores should be based on species-specific captive study results and relevant ecological data. Our results Suggest coyote feeding regimes may be improved by including unpredictable elements nested within a predictable framework to mirror seasonal fluctuations in resources and increase species-specific behaviour in Captivity. (C) 2009 Elsevier B.V. All rights reserved.
Abstract.
Jule KR, Lea SEG, Leaver LA (2009). Using a behaviour discovery curve to predict optimal observation time: captive red pandas (Aulurus fulgens) as a case study.
Behaviour,
146, 1531-1542.
Abstract:
Using a behaviour discovery curve to predict optimal observation time: captive red pandas (Aulurus fulgens) as a case study
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.
Abstract.
Hopewell LJ, Leaver LA, Lea SEG (2008). Effects of Competition and Food Availability on Travel Time in Scatter-hoarding Grey Squirrels (Sciurus carolinensis). Behavioral Ecology(19), 1143-1149.
Hopewell LJ, Leaver LA (2008). Evidence of social influences on cache-making by grey squirrels (Sciurus carolinensis). Ethology, 114, 1061-1068.
Jule K, Leaver L, Lea SEG (2008). The effects of captive experience on reintroduction survival in carnivores: a review and analysis.
Biological Conservation,
141, 355-363.
Abstract:
The effects of captive experience on reintroduction survival in carnivores: a review and analysis
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.
Abstract.
Leaver LA, Caldwell C, Hopewell L, Mallarky L (2007). Audience effects of food caching in grey squirrels (Sciurus carolinensis): evidence for pilferage avoidance strategies. Animal Cognition, 10(1), 23-27.
Hopewell LJ, Rossiter, R. Blower, E. Leaver, L. Goto K (2005). Grazing and vigilance by Soay Sheep on Lundy Island: influence of group size, terrain and the distribution of vegetation.
Behavioural Processes,
70, 186-193.
Author URL.
Leaver LA (2004). Effects of food value, predation risk and pilferage on the caching decisions of Dipodomys merriami. Behavioral Ecology, 15(5), 729-734.
Leaver LA, Daly M (2003). Effects of predation risk on selectivity in heteromyid rodents. Behavioural Processes, 64(1), 71-75.
Leaver LA, Daly M (2001). Food caching and differential cache pilferage: a field study of co-existence of sympatric kangaroo rats and pocket mice. Oecologia, 128(4), 577-584.
Leaver LA, Daly, M. (1998). Effects of food preference on scatter hoarding by kangaroo rats (Dipodomys merriami).
Behaviour,
135, 823-832.
Author URL.
Chapters
Leaver LA, Jayne K (2015). Strategic decisions made by small mammals during scatter hoarding, cache recovery and cache pilferage. In Shuttleworth C, Lurz P, Hayward M (Eds.) Red Squirrels: Ecology, Conservation & Management in Europe, European Squirrel Initiative, 51-65.
Conferences
Wilkes L, Leaver L, Sloman K, Readman G, Williams T, Owen S, Wilson R (2009). Development of enrichment criteria for zebrafish(<i>Danio rerio</i>) used in laboratory studies.
Author URL.
Landin J, Wilson R, Owen S, Williams T, Readman G, Sloman K, Leaver L (2009). Welfare and enrichment criteria for fish used in research.
Author URL.
Publications by year
In Press
Leaver L, Lea S, Chow P, McLaren I (In Press). Behavioral Flexibility: a review, a model and some exploratory tests. Learning and Behavior
Leaver L, Ford S, Miller C, Yeo M, Fawcett T (In Press). Learning is negatively associated with strength of left/right paw preference in wild grey squirrels (Sciurus carolinensis). Learning and Behavior
Lea SEG, Pothos E, Wills A, Leaver L, Ryan C, Meier C (In Press). Multiple feature use in pigeons’ category discrimination: the influence of stimulus set structure and the salience of stimulus differences. Journal of Experimental Psychology: Animal Learning and Cognition
2020
Leaver L, Wilkinson A (2020). A special issue in honour of Stephen Lea - a true comparative psychologist.
Learn Behav,
48(1), 7-8.
Author URL.
2017
Chow PKY, Leaver LA, Wang M, Lea SEG (2017). Touch screen assays of behavioural flexibility and error characteristics in Eastern grey squirrels (Sciurus carolinensis). Animal Cognition, 20(3), 459-471.
2016
Leaver LA, Jayne K, Lea SEG (2016). Behavioral flexibility versus rules of thumb: how do grey squirrels deal with conflicting risks?. Behavioral Ecology, 28(1), 186-192.
Chow PKY, Lea SEG, Leaver LA (2016). How practice makes perfect: the role of persistence, flexibility and learning in problem solving efficiency.
Animal Behaviour, 273-283.
Abstract:
How practice makes perfect: the role of persistence, flexibility and learning in problem solving efficiency
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.
Abstract.
2015
Jayne K, Lea SEG, Leaver LA (2015). Behavioural responses of Eastern grey squirrels, <i>Sciurus carolinensis</i>, to cues of risk while foraging.
BEHAVIOURAL PROCESSES,
116, 53-61.
Author URL.
Chow PKY, Leaver LA, Wang M, Lea SEG (2015). Serial Reversal Learning in Gray Squirrels: Learning Efficiency as a Function of Learning and Change of Tactics.
JOURNAL OF EXPERIMENTAL PSYCHOLOGY-ANIMAL LEARNING AND COGNITION,
41(4), 343-353.
Author URL.
Leaver LA, Jayne K (2015). Strategic decisions made by small mammals during scatter hoarding, cache recovery and cache pilferage. In Shuttleworth C, Lurz P, Hayward M (Eds.) Red Squirrels: Ecology, Conservation & Management in Europe, European Squirrel Initiative, 51-65.
2011
Farmer HL, Plowman AB, Leaver LA (2011). Role of vocalisations and social housing in breeding in captive howler monkeys (Alouatta caraya).
Applied Animal Behaviour Science,
134(3-4), 177-183.
Abstract:
Role of vocalisations and social housing in breeding in captive howler monkeys (Alouatta caraya)
Over the last 12 years the European captive population of black and gold howler monkeys, Alouatta caraya, has increased at a slow rate and many groups have not produced offspring. This study aims to determine the influence of social organisation of captive groups and both performing and hearing howl vocalisations on reproductive success. Data were extracted from the European Studbook to calculate three variables of female reproductive success per capita, for each year of their reproductively active life (from three years of age). Reproductive success for females was measured as the occurrence of a birth each year, the total number of births per year and the number of successful births per year (offspring surviving to one year of age). Male data were analysed separately, using behavioural observations in addition to studbook data, to determine the effect of daily howling rates on reproductive success (mean number of offspring surviving to one year of age). We found that more offspring were born to and survived (both P
Abstract.
2010
Hopewell LJ, Leaver LA, Lea SEG, Wills AJ (2010). Grey squirrels (Sciurus carolinensis) show a feature-negative effect specific to social learning.
Anim Cogn,
13(2), 219-227.
Abstract:
Grey squirrels (Sciurus carolinensis) show a feature-negative effect specific to social learning.
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.
Abstract.
Author URL.
Smulders T, Gould K, Leaver LA (2010). Using ecology to guide the study of cognitive and neural mechanisms of different aspects of spatial memory in food-hoarding animals.
Philosophical Transactions of the Royal Society B,
365, 883-900.
Abstract:
Using ecology to guide the study of cognitive and neural mechanisms of different aspects of spatial memory in food-hoarding animals
Understanding the survival value of behaviour does not tell us how the mechanisms that control this
behaviour work. Nevertheless, understanding survival value can guide the study of these mechanisms.
In this paper, we apply this principle to understanding the cognitive mechanisms that
support cache retrieval in scatter-hoarding animals. We believe it is too simplistic to predict that
all scatter-hoarding animals will outperform non-hoarding animals on all tests of spatial memory.
Instead, we argue that we should look at the detailed ecology and natural history of each species.
This understanding of natural history then allows us to make predictions about which aspects of
spatial memory should be better in which species. We use the natural hoarding behaviour of the
three best-studied groups of scatter-hoarding animals to make predictions about three aspects of
their spatial memory: duration, capacity and spatial resolution, and we test these predictions against
the existing literature. Having laid out how ecology and natural history can be used to predict
detailed cognitive abilities, we then suggest using this approach to guide the study of the neural
basis of these abilities. We believe that this complementary approach will reveal aspects of
memory processing that would otherwise be difficult to discover.
Abstract.
2009
Wills AJ, Lea SEG, Leaver LA, Osthaus B, Ryan CME, Suret MB, Bryant CML, Chapman SJA, Millar L (2009). A comparative analysis of the categorization of multidimensional stimuli: I. unidimensional classification does not necessarily imply analytic processing; evidence from pigeons (Columba livia), squirrels (Scurius carolinensis) and humans (Homo sapiens).
Journal of Comparative Psychology,
123(4), 391-405.
Abstract:
A comparative analysis of the categorization of multidimensional stimuli: I. unidimensional classification does not necessarily imply analytic processing; evidence from pigeons (Columba livia), squirrels (Scurius carolinensis) and humans (Homo sapiens)
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.
Abstract.
Lea SEG, Wills AJ, Leaver LA, Ryan CME, Bryant CML, Millar L (2009). A comparative analysis of the categorization of multidimensional stimuli: II. Strategic information search in humans (Homo sapiens) but not in pigeons (Columba livia).
Journal of Comparative Psychology,
123(4), 406-420.
Abstract:
A comparative analysis of the categorization of multidimensional stimuli: II. Strategic information search in humans (Homo sapiens) but not in pigeons (Columba livia)
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.
Abstract.
Wilkes L, Leaver L, Sloman K, Readman G, Williams T, Owen S, Wilson R (2009). Development of enrichment criteria for zebrafish(<i>Danio rerio</i>) used in laboratory studies.
Author URL.
Gilbert-Norton LB, Leaver LA, Shivik JA (2009). The effect of randomly altering the time and location of feeding on the behaviour of captive coyotes (Canis latrans).
APPL ANIM BEHAV SCI,
120(3-4), 179-185.
Abstract:
The effect of randomly altering the time and location of feeding on the behaviour of captive coyotes (Canis latrans)
Captive carnivores appear highly Susceptible to the negative effects of predictable feeding routines. Current research and reviews suggest feeding unpredictably may increase species typical behaviour, but positive results have been limited to a few species. Our objectives were to determine whether randomly altering the time and location of feeding increased species typical behaviour, or affected the temporal distribution of captive coyote (Canis latrans) behaviour. We assigned 12 coyotes individually to either a predictable or an unpredictable (in time and location) feeding condition and measured behaviours in the morning and evening. Overall, mean time spent foraging, travelling, resting or standing was similar in both conditions, but coyotes in the unpredictable condition marked (118 vs. 42: P= 0.01, one-tailed) and howled (81 vs. 24; P= 0.05, one-tailed) significantly more than coyotes in the predictable condition. There were also significant temporal differences (a.m. vs. p.m.) in behaviour between conditions. Specifically, coyotes fed predictably foraged (P = 0.03) and travelled (P = 0.03) more in the morning and rested (P = 0.03) more in the evening, whereas coyotes fed unpredictably howled (62 vs. 19; P = 0.03) and stood (P = 0.05) more in the morning and foraged (P = 0.03) more in the evening. Optimum predictability for captive carnivores should be based on species-specific captive study results and relevant ecological data. Our results Suggest coyote feeding regimes may be improved by including unpredictable elements nested within a predictable framework to mirror seasonal fluctuations in resources and increase species-specific behaviour in Captivity. (C) 2009 Elsevier B.V. All rights reserved.
Abstract.
Lea SEG, Wills AJ, Leaver LA (2009). Unidimensional vs Overall Similarity discrimination of multi-dimensional stimuli by pigeons, gray squirrels and undergraduates.
Jule KR, Lea SEG, Leaver LA (2009). Using a behaviour discovery curve to predict optimal observation time: captive red pandas (Aulurus fulgens) as a case study.
Behaviour,
146, 1531-1542.
Abstract:
Using a behaviour discovery curve to predict optimal observation time: captive red pandas (Aulurus fulgens) as a case study
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.
Abstract.
Landin J, Wilson R, Owen S, Williams T, Readman G, Sloman K, Leaver L (2009). Welfare and enrichment criteria for fish used in research.
Author URL.
2008
Hopewell LJ, Leaver LA, Lea SEG (2008). Effects of Competition and Food Availability on Travel Time in Scatter-hoarding Grey Squirrels (Sciurus carolinensis). Behavioral Ecology(19), 1143-1149.
Hopewell LJ, Leaver LA (2008). Evidence of social influences on cache-making by grey squirrels (Sciurus carolinensis). Ethology, 114, 1061-1068.
Jule K, Leaver L, Lea SEG (2008). The effects of captive experience on reintroduction survival in carnivores: a review and analysis.
Biological Conservation,
141, 355-363.
Abstract:
The effects of captive experience on reintroduction survival in carnivores: a review and analysis
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.
Abstract.
2007
Leaver LA, Caldwell C, Hopewell L, Mallarky L (2007). Audience effects of food caching in grey squirrels (Sciurus carolinensis): evidence for pilferage avoidance strategies. Animal Cognition, 10(1), 23-27.
2005
Hopewell LJ, Rossiter, R. Blower, E. Leaver, L. Goto K (2005). Grazing and vigilance by Soay Sheep on Lundy Island: influence of group size, terrain and the distribution of vegetation.
Behavioural Processes,
70, 186-193.
Author URL.
2004
Leaver LA (2004). Effects of food value, predation risk and pilferage on the caching decisions of Dipodomys merriami. Behavioral Ecology, 15(5), 729-734.
2003
Leaver LA, Daly M (2003). Effects of predation risk on selectivity in heteromyid rodents. Behavioural Processes, 64(1), 71-75.
2001
Leaver LA, Daly M (2001). Food caching and differential cache pilferage: a field study of co-existence of sympatric kangaroo rats and pocket mice. Oecologia, 128(4), 577-584.
1998
Leaver LA, Daly, M. (1998). Effects of food preference on scatter hoarding by kangaroo rats (Dipodomys merriami).
Behaviour,
135, 823-832.
Author URL.
