Showing papers in "Animal Cognition in 2012"
TL;DR: Here, it is explained how an integration of comparative psychology and evolutionary biology will answer a host of questions regarding the phylogenetic distribution and history of cognitive traits, as well as the evolutionary processes that drove their evolution.
Abstract: Now more than ever animal studies have the potential to test hypotheses regarding how cognition evolves. Comparative psychologists have developed new techniques to probe the cognitive mechanisms underlying animal behavior, and they have become increasingly skillful at adapting methodologies to test multiple species. Meanwhile, evolutionary biologists have generated quantitative approaches to investigate the phylogenetic distribution and function of phenotypic traits, including cognition. In particular, phylogenetic methods can quantitatively (1) test whether specific cognitive abilities are correlated with life history (e.g., lifespan), morphology (e.g., brain size), or socio-ecological variables (e.g., social system), (2) measure how strongly phylogenetic relatedness predicts the distribution of cognitive skills across species, and (3) estimate the ancestral state of a given cognitive trait using measures of cognitive performance from extant species. Phylogenetic methods can also be used to guide the selection of species comparisons that offer the strongest tests of a priori predictions of cognitive evolutionary hypotheses (i.e., phylogenetic targeting). Here, we explain how an integration of comparative psychology and evolutionary biology will answer a host of questions regarding the phylogenetic distribution and history of cognitive traits, as well as the evolutionary processes that drove their evolution.
230 citations
TL;DR: Dogs’ pattern of response was behaviorally consistent with an expression of empathic concern, but is most parsimoniously interpreted as emotional contagion coupled with a previous learning history in which they have been rewarded for approaching distressed human companions.
Abstract: Empathy covers a range of phenomena from cognitive empathy involving metarepresentation to emotional contagion stemming from automatically triggered reflexes. An experimental protocol first used with human infants was adapted to investigate empathy in domestic dogs. Dogs oriented toward their owner or a stranger more often when the person was pretending to cry than when they were talking or humming. Observers, unaware of experimental hypotheses and the condition under which dogs were responding, more often categorized dogs’ approaches as submissive as opposed to alert, playful or calm during the crying condition. When the stranger pretended to cry, rather than approaching their usual source of comfort, their owner, dogs sniffed, nuzzled and licked the stranger instead. The dogs’ pattern of response was behaviorally consistent with an expression of empathic concern, but is most parsimoniously interpreted as emotional contagion coupled with a previous learning history in which they have been rewarded for approaching distressed human companions.
165 citations
TL;DR: Most dogs appear to seek information about the environment from the human, but little differences were found between dogs in the positive and negative groups as regards behavioural regulation: possible explanations for this are discussed.
Abstract: Social referencing is the seeking of information from another individual to form one's own understanding and guide action. In this study, adult dogs were tested in a social referencing paradigm involving their owner and a potentially scary object. Dogs received either a positive or negative message from the owner. The aim was to evaluate the presence of referential looking to the owner, behav- ioural regulation based on the owner's (vocal and facial) emotional message and observational conditioning follow- ing the owner's actions towards the object. Most dogs (83%) looked referentially to the owner after looking at the strange object, thus they appear to seek information about the environment from the human, but little diVerences were found between dogs in the positive and negative groups as regards behavioural regulation: possible explanations for this are discussed. Finally, a strong eVect of observational conditioning was found with dogs in the positive group moving closer to the fan and dogs in the negative group moving away, both mirroring their owner's behaviour. Results are discussed in relation to studies on human-dog communication, attachment and social learning.
122 citations
TL;DR: Performance supports an accumulator model in which quantities are represented as analog magnitudes, and no effect of absolute magnitude on performance is found, providing support against an object-file model explanation of quantity judgment.
Abstract: The ability to discriminate between quantities has been observed in many species. Typically, when an animal is given a choice between two sets of food, accurate performance (i.e., choosing the larger amount) decreases as the ratio between two quantities increases. A recent study reported that elephants did not exhibit ratio effects, suggesting that elephants may process quantitative information in a qualitatively different way from all other nonhuman species that have been tested (Irie-Sugimoto et al. in Anim Cogn 12:193–199, 2009). However, the results of this study were confounded by several methodological issues. We tested two African elephants (Loxodonta africana) to more thoroughly investigate relative quantity judgment in this species. In contrast to the previous study, we found evidence of ratio effects for visible and nonvisible sequentially presented sets of food. Thus, elephants appear to represent and compare quantities in much the same way as other species, including humans when they are prevented from counting. Performance supports an accumulator model in which quantities are represented as analog magnitudes. Furthermore, we found no effect of absolute magnitude on performance, providing support against an object-file model explanation of quantity judgment.
103 citations
TL;DR: The results suggest that cognitive mechanism influencing an understanding of physical quantity may be deployed more flexibly in some contexts than previously thought, and are discussed in light of findings across other mammalian and avian species.
Abstract: While numerosity—representation and enu- meration of different numbers of objects—and quantity discrimination in particular have been studied in a wide range of species, very little is known about the numerical abilities of animals in the wild. This study examined spontaneous relative quantity judgments (RQJs) by wild North Island robins (Petroica longipes) of New Zealand. In Experiment 1, robins were tested on a range of numerical values of up to 14 versus 16 items, which were sequentially presented and hidden. In Experiment 2, the same numerical contrasts were tested on a different group of subjects but quantities were presented as whole visible sets. Experiment 3 involved whole visible sets that comprised of exceed- ingly large quantities of up to 56 versus 64 items. While robins shared with other species a ratio-based representa- tion system for representing very large values, they also appeared to have developed an object indexing system with an extended upper limit (well beyond 4) that may be an evolutionary response to ecological challenges faced by scatter-hoarding birds. These results suggest that cognitive mechanism influencing an understanding of physical quantity may be deployed more flexibly in some contexts than previously thought, and are discussed in light of findings across other mammalian and avian species.
93 citations
TL;DR: It is found that dogs focused their attention on the informative regions of the images without any task-specific pre-training and their gazing behavior depended on the image category, which indicated dogs’ attraction to conspecifics over human faces and inanimate objects might reflect their natural interest.
Abstract: Despite intense research on the visual communication of domestic dogs, their cognitive capacities have not yet been explored by eye tracking. The aim of the current study was to expand knowledge on the visual cognition of dogs using contact-free eye movement tracking under conditions where social cueing and associative learning were ruled out. We examined whether dogs spontaneously look at actual objects within pictures and can differentiate between pictures according to their novelty or categorical information content. Eye movements of six domestic dogs were tracked during presentation of digital color images of human faces, dog faces, toys, and alphabetic characters. We found that dogs focused their attention on the informative regions of the images without any task-specific pre-training and their gazing behavior depended on the image category. Dogs preferred the facial images of conspecifics over other categories and fixated on a familiar image longer than on novel stimuli regardless of the category. Dogs' attraction to conspecifics over human faces and inanimate objects might reflect their natural interest, but further studies are needed to establish whether dogs possess picture object recognition. Contact-free eye movement tracking is a promising method for the broader exploration of processes underlying special socio-cognitive skills in dogs previously found in behavioral studies.
87 citations
TL;DR: Fish succeed at comparisons between large numbers only, but systematically fail at comparisons that closely span the small/large boundary, and a pattern of successes and failures similar to those observed in human infants is found to suggest that the two systems are present and functionally distinct across a wide variety of animal species.
Abstract: Non-verbal numerical behavior in human infants, human adults, and non-human primates appears to be rooted in two distinct mechanisms: a precise system for tracking and comparing small numbers of items simultaneously (up to 3 or 4 items) and an approximate system for estimating numerical magnitude of a group of objects. The most striking evidence that these two mechanisms are distinct comes from the apparent inability of young human infants and non-human primates to compare quantites across the small ( 4) number boundary. We ask whether this distinction is present in lower animal species more distantly related to humans, guppies (Poecilia reticulata). We found that, like human infants and non-human primates, fish succeed at comparisons between large numbers only (5 vs. 10), succeed at comparisons between small numbers only (3 vs. 4), but systematically fail at comparisons that closely span the small/large boundary (3 vs. 5). Furthermore, increasing the distance between the small and large number resulted in successful discriminations (3 vs. 6, 3 vs. 7, and 3 vs. 9). This pattern of successes and failures is similar to those observed in human infants and non-human primates to suggest that the two systems are present and functionally distinct across a wide variety of animal species.
79 citations
TL;DR: This study provides first data that renders plausible empathy-based, emotionally connected, contagious yawning in dogs, in a way that is unaffected by social–emotional factors.
Abstract: Dogs’ capacity to ‘catch’ human yawns has recently attracted the attention of researchers in the field of animal cognition. Following recent studies suggesting that contagion yawning in humans, and some other primates, is empathy-related, some authors have considered the possibility that the same mechanism may underlie contagious yawning in dogs. To date, however, no positive evidence has been found, and more parsimonious hypotheses have been put forward. The present study explored the ‘contagion-only’ hypothesis by testing whether the mere sound of a human yawn can be sufficient to elicit yawning in dogs, in a way that is unaffected by social–emotional factors. Unexpectedly, results showed an interesting interplay between contagion and social effects. Not only were dogs found to catch human yawns, but they were also found to yawn more at familiar than unfamiliar yawns. Although not allowing for conclusive inferences about the mechanisms underlying contagious yawning in dogs, this study provides first data that renders plausible empathy-based, emotionally connected, contagious yawning in these animals.
76 citations
TL;DR: Overall, the findings indicate that individuals vary in their sensitivity to distance of transport, a few meters are perceived as a substantive cost by some monkeys, and monkeys’ body mass affects their decisions.
Abstract: Contemporary optimization models suggest that animals optimize benefits of foraging and minimize its costs. For wild bearded capuchins (Sapajuslibidinosus), nut-cracking entails cost related to lifting the heavy stone and striking the nut and additional cost to transport the stone if it is not already on the anvil. To assess the role of stone mass and transport distance in capuchins’ tool selection, we carried out three field experiments. In Experiment 1, we investigated whether transport distance affected choice of a tool by positioning two stones of the same mass close and far from the anvil. Capuchins consistently selected the closer stone, effectively reducing transport costs. In Experiment 2, we examined the trade-off between the cost of transport and the effectiveness in cracking by positioning two stones of different mass close and far from the anvil. Most subjects significantly preferred the closer stone, regardless of mass, whereas others preferred the heavier stone regardless of transport distance. In Experiment 3, we changed transport distance of both stones while maintaining the same distance ratios as in Experiment 2. Capuchins maintained the preferences expressed in Experiment 2, with the exception of one subject. Overall, our findings indicate that (1) individuals vary in their sensitivity to distance of transport, (2) a few meters are perceived as a substantive cost by some monkeys, and (3) monkeys’ body mass affects their decisions. We also developed a non-dimensional Preference index (P) defined as a function of the stone mass and the transport distance to describe monkey’s choice.
73 citations
TL;DR: Bidirectional generalization indicates that use of the decline response by monkeys is not controlled by specific external stimuli but is rather a flexible behavior based on a private assessment of memory.
Abstract: The possibility that memory awareness occurs in nonhuman animals has been evaluated by providing opportunity to decline memory tests. Current evidence suggests that rhesus monkeys (Macaca mulatta) selectively decline tests when memory is weak (Hampton in Proc Natl Acad Sci USA 98:5359–5362, 2001; Smith et al. in Behav Brain Sci 26:317–374, 2003). However, much of the existing research in nonhuman metacognition is subject to the criticism that, after considerable training on one test type, subjects learn to decline difficult trials based on associative learning of external test-specific contingencies rather than by evaluating the private status of memory or other cognitive states. We evaluated whether such test-specific associations could account for performance by presenting monkeys with a series of generalization tests across which no single association with external stimuli was likely to adaptively control use of the decline response. Six monkeys performed a four alternative delayed matching to location task and were significantly more accurate on trials with a decline option available than on trials without it, indicating that subjects selectively declined tests when memory was weak. Monkeys transferred appropriate use of the decline response under three conditions that assessed generalization: two tests that weakened memory and one test that enhanced memory in a novel way. Bidirectional generalization indicates that use of the decline response by monkeys is not controlled by specific external stimuli but is rather a flexible behavior based on a private assessment of memory.
68 citations
TL;DR: This study is the first to reveal a positive correlation between levels of stereotypic behaviour and a ‘pessimistic’-like judgment bias in a non-human primate by employing a recently developed cognitive approach.
Abstract: Abnormal stereotypic behaviour is widespread among captive non-human primates and is generally associated with jeopardized well-being. However, attributing the same significance to all of these repetitive, unvarying and apparently functionless behaviours may be misleading, as some behaviours may be better indicators of stress than others. Previous studies have demonstrated that the affective state of the individual can be inferred from its bias in appraising neutral stimuli in its environment. Therefore, in the present study, in order to assess the emotional state of stereotyping individuals, 16 captive tufted capuchins (Cebus apella) were tested on a judgment bias paradigm and their faecal corticoid levels were measured in order to assess the intensity of the emotional state. Capuchins with higher levels of stereotypic head twirls exhibited a negative bias while judging ambiguous stimuli and had higher levels of faecal corticoids compared to subjects with lower levels of head twirls. Levels of stereotypic pacing, however, were not correlated with the monkeys’ emotional state. This study is the first to reveal a positive correlation between levels of stereotypic behaviour and a ‘pessimistic’-like judgment bias in a non-human primate by employing a recently developed cognitive approach. Combining cognitive tests that evaluate the animals’ affective valence (positive or negative) with hormonal measurements that provide information on the strength of the emotional state conduces to a better understanding of the animals’ affective state and therefore to their well-being.
TL;DR: The equine brain is able to integrate multisensory identity cues from a familiar human into a person representation that allows the brain, when deprived of one or two senses, to maintain recognition of this person.
Abstract: This study has shown that domestic horses are capable of cross-modal recognition of familiar humans. It was demonstrated that horses are able to discriminate between the voices of a familiar and an unfamiliar human without seeing or smelling them at the same moment. Conversely, they were able to discriminate the same persons when only exposed to their visual and olfactory cues, without being stimulated by their voices. A cross-modal expectancy violation setup was employed; subjects were exposed both to trials with incongruent auditory and visual/olfactory identity cues and trials with congruent cues. It was found that subjects responded more quickly, longer and more often in incongruent trials, exhibiting heightened interest in unmatched cues of identity. This suggests that the equine brain is able to integrate multisensory identity cues from a familiar human into a person representation that allows the brain, when deprived of one or two senses, to maintain recognition of this person.
TL;DR: It is indicated that symbolic stimuli fail to facilitate delay maintenance when they do not abstract away from the quantitative dimension of the task, consistent with previous findings on the effects of symbols on self-control and illuminates what makes accumulation a particularly challenging task.
Abstract: Capuchin monkeys have been tested for the capacity to delay gratification for accumulating rewards in recent studies and have exhibited variable results. Meanwhile, chimpanzees have consistently excelled at this task. However, neither species have ever been tested at accumulating symbolic tokens instead of food items, even though previous reports indicate that tokens sometimes facilitate performance in other self-control tasks. Thus, in the present study, we tested capuchin monkeys and chimpanzees for their capacity to delay gratification in a delay maintenance task, in which an experimenter presented items, one at a time, to within reach of an animal for as long as the animal refrained from taking them. In Experiment 1, we assessed how long capuchin monkeys could accumulate items in the delay maintenance task when items were food rewards or tokens exchangeable for food rewards. Monkeys accumulated more food rewards than they did tokens. In Experiment 2, we tested capuchin monkeys and chimpanzees in a similar accumulation test. Whereas capuchins again accumulated more food than tokens, all chimpanzees but one showed no difference in performance in the two conditions. These findings provide additional evidence that chimpanzees exhibit greater self-control capacity in this task than do capuchin monkeys and indicate that symbolic stimuli fail to facilitate delay maintenance when they do not abstract away from the quantitative dimension of the task. This is consistent with previous findings on the effects of symbols on self-control and illuminates what makes accumulation a particularly challenging task.
TL;DR: The experiments suggest that personality in great tits is not strongly related to learning per se in such an association task, but that birds from different selection lines might express different learning strategies as birds from the different selection Lines were differently affected by their previous learning performance.
Abstract: In animals, individual differences in learning ability are common and are in part explained by genetic differences, developmental conditions and by general experience. Yet, not all variations in learning are well understood. Individual differences in learning may be associated with elementary individual characteristics that are consistent across situations and over time, commonly referred to as personality or temperament. Here, we tested whether or not male great tits (Parus major) from two selection lines for fast or slow exploratory behaviour, an operational measure for avian personality, vary in their learning performance in two related consecutive tasks. In the first task, birds had to associate a colour with a reward whereas in the second task, they had to associate a new colour with a reward ignoring the previously rewarded colour. Slow explorers had shorter latencies to approach the experimental device compared with fast explorers in both tasks, but birds from the two selection lines did not differ in accomplishing the first task, that is, to associate a colour with a reward. However, in the second task, fast explorers had longer latencies to solve the trials than slow explorers. Moreover, relative to the number of trials needed to reach the learning criteria in the first task, birds from the slow selection line took more trials to associate a new colour with a reward while ignoring the previously learned association compared with birds from the fast selection line. Overall, the experiments suggest that personality in great tits is not strongly related to learning per se in such an association task, but that birds from different selection lines might express different learning strategies as birds from the different selection lines were differently affected by their previous learning performance.
TL;DR: This study investigated extensively the vocal behaviour of free-ranging and individually identified Diana monkeys in non-predatory contexts and demonstrated that some non-human primates are able to increase the effective size of their small vocal repertoire by varying the acoustic structure of basic call types but also by combining them into more complex structures.
Abstract: Non-human primates possess species-specific repertoires of acoustically distinct call types that can be found in adults in predictable ways. Evidence for vocal flexibility is generally rare and typically restricted to acoustic variants within the main call types or sequential production of multiple calls. So far, evidence for context-specific call sequences has been mainly in relation to external disturbances, particularly predation. In this study, we investigated extensively the vocal behaviour of free-ranging and individually identified Diana monkeys in non-predatory contexts. We found that adult females produced four vocal structures alone ('H', 'L', 'R' and 'A' calls, the latter consisting of two subtypes) or combined in non-random ways ('HA', 'LA' and 'RA' call combinations) in relation to ongoing behaviour or external events. Specifically, the concatenation of an introductory call with the most frequently emitted and contextually neutral 'A' call seems to function as a contextual refiner of this potential individual identifier. Our results demonstrate that some non-human primates are able to increase the effective size of their small vocal repertoire not only by varying the acoustic structure of basic call types but also by combining them into more complex structures. We have demonstrated this phenomenon for a category of vocalisations with a purely social function and discuss the implications of these findings for evolutionary theories of primate vocal communication.
TL;DR: In the present research, more lifelike situations are modelled in contrast to previous studies which often relied on using only two potential hiding locations and direct association between the communicative signal and the signalled object.
Abstract: The aim of the present investigation was to study the visual communication between humans and dogs in relatively complex situations. In the present research, we have modelled more lifelike situations in contrast to previous studies which often relied on using only two potential hiding locations and direct association between the communicative signal and the signalled object. In Study 1, we have provided the dogs with four potential hiding locations, two on each side of the experimenter to see whether dogs are able to choose the correct location based on the pointing gesture. In Study 2, dogs had to rely on a sequence of pointing gestures displayed by two different experimenters. We have investigated whether dogs are able to recognise an ‘indirect signal’, that is, a pointing toward a pointer. In Study 3, we have examined whether dogs can understand indirect information about a hidden object and direct the owner to the particular location. Study 1 has revealed that dogs are unlikely to rely on extrapolating precise linear vectors along the pointing arm when relying on human pointing gestures. Instead, they rely on a simple rule of following the side of the human gesturing. If there were more targets on the same side of the human, they showed a preference for the targets closer to the human. Study 2 has shown that dogs are able to rely on indirect pointing gestures but the individual performances suggest that this skill may be restricted to a certain level of complexity. In Study 3, we have found that dogs are able to localise the hidden object by utilising indirect human signals, and they are able to convey this information to their owner.
TL;DR: The results of studies on invertebrates are synthesized and a framework is provided with the purpose of identifying research needs and directions for future investigations and illustrating eight key properties that characterize ‘true individual recognition’ systems.
Abstract: Since the 1970s, the ability of some invertebrate species to recognize individual conspecifics has attracted increased scientific interest. However, there is still confusion in the literature, possibly due to the lack of unambiguous criteria for classifying social recognition in its different forms. Here, we synthesize the results of studies on invertebrates and provide a framework with the purpose of identifying research needs and directions for future investigations. Following in part Sherman et al.’s (Behavioural ecology: an evolutionary approach. Blackwell Science, Oxford, pp 69–96, 1997) definition of ‘recognition systems’ and Tibbetts and Dale’s (Trends Ecol Evol 22:529–537, 2007) classification of ‘individual recognition,’ we first discuss different case studies that exemplify the categories of ‘familiar recognition’ and ‘class-level recognition.’ Then, through the analysis of the invertebrate literature, we illustrate eight key properties that characterize ‘true individual recognition’ systems. We are confident that the proposed framework will provide opportunities for exciting discoveries of the cognitive abilities in invertebrates.
TL;DR: Redfronted lemurs appear to use social information in acquiring a novel task, and animals in at least in one group without training developed a group preference for one technique, indicating that they have the potential to develop behavioural traditions and conformity.
Abstract: Recent research has claimed that traditions are not a unique feature of human culture, but that they can be found in animal societies as well. However, the origins of traditions in animals studied in the wild are still poorly understood. To contribute comparative data to begin filling this gap, we conducted a social diffusion experiment with four groups of wild redfronted lemurs (Eulemur rufifrons). We used a ‘two-option’ feeding box, where these Malagasy primates could either pull or push a door to get access to a fruit reward to study whether and how these two behavioural traits spread through the groups. During a pre-training phase, two groups were presented with boxes in which one technique was blocked, whereas two groups were presented with unblocked boxes. During a subsequent unconstrained phase, all four groups were confronted with unblocked boxes. Nearly half of the study animals were able to learn the new feeding skill and individuals who observed others needed fewer unsuccessful task manipulations until their first successful action. Animals in the two groups with pre-training also discovered the corresponding alternative technique but preferred the seeded technique. Interestingly, animals in the two groups without pre-training discovered both techniques, and one group developed a group preference for one technique whereas the other did not. In all groups, some animals also scrounged food rewards. In conclusion, redfronted lemurs appear to use social information in acquiring a novel task, and animals in at least in one group without training developed a group preference for one technique, indicating that they have the potential to develop behavioural traditions and conformity.
TL;DR: Investigation of how numerical competence is expressed in a highly specialized predatory strategy adopted by the small juveniles of Portiaafricana when practicing communal predation suggests that P. africana juveniles base settling decisions on the specific number of already settled conspecific juveniles at the nest and express a preference for settling when the number is one instead of zero, two or three.
Abstract: Although a wide range of vertebrates have been considered in research on numerical competence, little is known about the role of number-related decisions in the predatory strategies of invertebrates. Here, we investigate how numerical competence is expressed in a highly spe- cialized predatory strategy adopted by the small juveniles of Portia africana when practicing communal predation, with the prey being another spider, Oecobius amboseli. Two or more P. africana juveniles sometimes settle by the same oecobiid nest and then share the meal after one individual captures the oecobiid. Experiments were designed to clarify how these predators use number-related cues in conjunction with non-numerical cues when decid- ing whether to settle at a nest. We used lures (dead spiders positioned in lifelike posture) arranged in a series of 24 different scenes defined by the type, configuration and especially number of lures. On the whole, our findings suggest that P. africana juveniles base settling decisions on the specific number of already settled conspecific juveniles at the nest and express a preference for settling when the number is one instead of zero, two or three. By varying the size of the already settled juveniles and their positions around the nest, we show that factors related to continuous variables and stimulus configuration are unlikely explana- tions for our findings.
TL;DR: It is postulated that a right-hand bias for only inanimate targets reflects the left hemisphere’s dominant neural processing capabilities for objects that have functional properties (inanimate objects) and is not a human-unique characteristic, but one that was inherited from a common human-ape ancestor.
Abstract: We employed a bottom-up, quantitative method to investigate great ape handedness. Our previous investigation of gorillas (Gorilla gorilla gorilla) demonstrated that contextual information influenced an individual’s handedness toward target objects. Specifically, we found a significant right-hand bias for unimanual actions directed toward inanimate target objects but not for actions directed to animate target objects (Forrester et al. in Anim Cogn 14(6):903–907, 2011). Using the identical methodological technique, we investigated the spontaneous hand actions of nine captive chimpanzees (Pan troglodytes) during naturalistic, spontaneous behavior. We assessed both the frequencies and proportions of lateralized hand actions directed toward animate and inanimate targets employing focal follow video sampling. Like the gorillas, the chimpanzees demonstrated a right-handed bias for actions directed toward inanimate targets, but not toward animate targets. This pattern was evident at the group level and for the majority of subjects at the individual level. We postulate that a right-hand bias for only inanimate targets reflects the left hemisphere’s dominant neural processing capabilities for objects that have functional properties (inanimate objects). We further speculate that a population-level right-hand bias is not a human-unique characteristic, but one that was inherited from a common human-ape ancestor.
TL;DR: This article showed that a grey parrot (Psittacus erithacus) was able to quantify sets of eight or fewer items (including heterogeneous subsets), to sum two sequentially presented sets of 0-6 items (up to 6), and to identify and serially order Arabic numerals (1-8), all by using English labels.
Abstract: A Grey parrot (Psittacus erithacus), able to quantify sets of eight or fewer items (including heterogeneous subsets), to sum two sequentially presented sets of 0–6 items (up to 6), and to identify and serially order Arabic numerals (1–8), all by using English labels (Pepperberg in J Comp Psychol 108:36–44, 1994; J Comp Psychol 120:1–11, 2006a; J Comp Psychol 120:205–216, 2006b; Pepperberg and Carey submitted), was tested on addition of two Arabic numerals or three sequentially presented collections (e.g., of variously sized jelly beans or nuts). He was, without explicit training and in the absence of the previously viewed addends, asked, “How many total?” and required to answer with a vocal English number label. In a few trials on the Arabic numeral addition, he was also shown variously colored Arabic numerals while the addends were hidden and asked “What color number (is the) total?” Although his death precluded testing on all possible arrays, his accuracy was statistically significant and suggested addition abilities comparable with those of nonhuman primates.
TL;DR: Compared to primates, dogs tolerated relatively long delays for smaller value rewards, suggesting that the socio-ecological history of domestic dogs facilitates their performance on decision-making and delay of gratification tasks.
Abstract: Five domestic dogs (Canis familiaris) were tested in a cooperative exchange task with an experimenter, as previously tested in non-human primates. In the first task, the dogs exchanged to maximise payoffs when presented with food items of differing quality. All consistently exchanged lower-value for higher-value rewards, as determined by their individual food preference, and exchanges corresponded significantly with the spontaneous preferences of three dogs. Next, all subjects demonstrated an ability to perform two and three exchanges in succession, to gain both qualitative and quantitatively increased rewards (group mean = 72 and 92% successful triple exchanges, respectively). Finally, the ability to delay gratification over increasing intervals was tested; the dogs kept one food item to exchange later for a larger item. As previously reported in non-human primates, there was considerable individual variation in the tolerance of delays, between 10 s and 10 min for the largest rewards. For those who reached longer time lags (>40 s), the dogs gave up the chance to exchange earlier than expected by each subject’s general waiting capacity; the dogs anticipated delay duration and made decisions according to the relative reward values offered. Compared to primates, dogs tolerated relatively long delays for smaller value rewards, suggesting that the socio-ecological history of domestic dogs facilitates their performance on decision-making and delay of gratification tasks.
TL;DR: The results of the present study indicate that dogs may have a limited understanding of physical problems and how they can be solved by a human partner, Nevertheless, dogs are able to adjust their behavior to situation-specific characteristics of their human partner’s behavior.
Abstract: Domestic dogs (Canis familiaris) have been shown to actively initiate triadic communicative interactions by looking at a human partner or by alternating their gaze between the human and an object when being faced with an out-of-reach reward or an unsolvable problem. It has hardly been investigated, however, whether dogs flexibly adjust their human-directed behavior to the actions of their partners, which indicate their willingness and abilities to help them when they are faced with a problem. Here, in two experiments, we confronted dogs—after initially allowing them to learn how to manipulate an apparatus—with two problem situations: with an empty apparatus and a blocked apparatus. In Experiment 1, we showed that dogs looked back at their owners more when the owners had previously encouraged them, independently from the problem they faced. In Experiment 2, we provided dogs with two experimenters and allowed them to learn through an initial phase that each of the experimenters could solve one of the two problems: the Filler re-baited the empty apparatus and the Helper unblocked the blocked apparatus. We found that dogs could learn to recognize the ability of the Filler and spent time close to her when the apparatus was empty. Independently from the problem, however, they always approached the Helper first. The results of the present study indicate that dogs may have a limited understanding of physical problems and how they can be solved by a human partner. Nevertheless, dogs are able to adjust their behavior to situation-specific characteristics of their human partner’s behavior.
TL;DR: It is found that the presence of spotting significantly decreased the probability of rejection while increments in brightness significantly increased rejection frequencies, and the cognitive rules underlying mockingbird rejection behavior can be explained by a decision-making model which predicts changes in the levels of rejection in direct relation to the number of relevant attributes shared between host and parasite eggs.
Abstract: Brood parasitism imposes several fitness costs on the host species. To reduce these costs, hosts of avian brood parasites have evolved various defenses, of which egg rejection is the most prevalent. In the face of variable host-parasite mimicry and the costs of egg discrimination itself, many hosts reject only some foreign eggs. Here, we experimentally varied the recognition cues to study the underlying cognitive mechanisms used by the Chalk-browed Mockingbird (Mimus saturninus) to reject the white immaculate eggs laid by the parasitic Shiny Cowbird (Molothrus bonariensis). Immaculate eggs are the only parasite eggs rejected by this host, as it accepts all polymorphic, spotted eggs laid by cowbirds. Using a within-breeding pair experimental design, we tested for the salience of spotting, UV reflectance, and brightness in eliciting rejection. We found that the presence of spotting significantly decreased the probability of rejection while increments in brightness significantly increased rejection frequencies. The cognitive rules underlying mockingbird rejection behavior can be explained by a decision-making model which predicts changes in the levels of rejection in direct relation to the number of relevant attributes shared between host and parasite eggs.
TL;DR: This is the first report of tool-using behaviour in a wild brown bear (Ursus arctos) and it clearly shows that these animals possess the advanced motor learning necessary for tool-use.
Abstract: This is the first report of tool-using behaviour in a wild brown bear (Ursus arctos). Whereas the use of tools is comparatively common among primates and has also been documented in several species of birds, fishes and invertebrates, tool-using behaviours have so far been observed in only four species of non-primate mammal. The observation was made and photographed while studying the behaviour of a subadult brown bear in south-eastern Alaska. The animal repeatedly picked up barnacle-encrusted rocks in shallow water, manipulated and re-oriented them in its forepaws, and used them to rub its neck and muzzle. The behaviour probably served to relieve irritated skin or to remove food-remains from the fur. Bears habitually rub against stationary objects and overturn rocks and boulders during foraging and such rubbing behaviour could have been transferred to a freely movable object to classify as tool-use. The bear exhibited considerable motor skills when manipulating the rocks, which clearly shows that these animals possess the advanced motor learning necessary for tool-use. Advanced spatial cognition and motor skills for object manipulation during feeding and tool-use provide a possible explanation for why bears have the largest brains relative to body size of all carnivores. Systematic research into the cognitive abilities of bears, both in captivity and in the wild, is clearly warranted to fully understand their motor-learning skills and physical intelligence related to tool-use and other object manipulation tasks.
TL;DR: The results suggest that animals that succeed in this information-seeking task are not merely acting according to a generalized search strategy, and instead seek information adaptively according to their knowledge states.
Abstract: Recent empirical work has suggested that some species of non-human primates may be aware of their knowledge states. One finding to support this claim is that they seek information about the location of a hidden food item when they are unsure of its location, but not when they already know where it is, which purportedly demonstrates metacognition. However, this behaviour may instead reflect a generalized search strategy, in which subjects reach for food when they see it, and search for it when they do not. In this experiment, this possibility was addressed by testing orangutans in three conditions in which the location of a food item was sometimes known to subjects, and other times required subjects to visually seek the missing information. All subjects exhibited behaviour consistent with a metacognitive interpretation in at least two of the three conditions. Critically, in two of the conditions, subjects refrained from seeking visual information, and correctly found the hidden food item without ever seeing it, using inference by exclusion. The results suggest that animals that succeed in this information-seeking task are not merely acting according to a generalized search strategy, and instead seek information adaptively according to their knowledge states.
TL;DR: This study studied whether rainforest primates, grey-cheeked mangabeys in the Kibale National Park, Uganda, used synchrony in fruit emergence to find fruit, finding no indication that the monkeys generalised this strategy to all Uvariopsis trees within their home range.
Abstract: Previous research has shown that a considerable number of primates can remember the location and fruiting state of individual trees in their home range. This enables them to relocate fruit or predict whether previously encountered fruit has ripened. Recent studies, however, suggest that the ability of primates to cognitively map fruit-bearing trees is limited. In this study, we investigated an alternative and arguably simpler, more efficient strategy, the use of synchrony, a botanical characteristic of a large number of fruit species. Synchronous fruiting would allow the prediction of the fruiting state of a large number of trees without having to first check the trees. We studied whether rainforest primates, grey-cheeked mangabeys in the Kibale National Park, Uganda, used synchrony in fruit emergence to find fruit. We analysed the movements of adult males towards Uvariopsis congensis food trees, a strongly synchronous fruiting species with different local patterns of synchrony. Monkeys approached within crown distance, entered and inspected significantly more Uvariopsis trees when the percentage of trees with ripe fruit was high compared to when it was low. Since the effect was also found for empty trees, the monkeys likely followed a synchrony-based inspection strategy. We found no indication that the monkeys generalised this strategy to all Uvariopsis trees within their home range. Instead, they attended to fruiting peaks in local areas within the home range and adjusted their inspective behaviour accordingly revealing that non-human primates use botanical knowledge in a flexible way.
TL;DR: Rats’ exploratory behavior in response to door manipulations that either strongly altered or did not alter the ability to commute between sectors implies that during exploration rats build a precise map of the connectivity of space that can be flexibly updated and used for efficient navigation.
Abstract: Although rats are able to build complex spatial representations of their surroundings during exploration, the nature of the encoded information is still a matter for debate. In particular, it is not well established if rats can process the topological structure of the environment in such a way that they are aware of the connections existing between remote places. Here, rats were first exposed for four 5-min trials to a complex environment divided into several sectors that were separated by doors allowing either unrestricted or restricted access to other sectors. In the fifth test trial, we measured the behavior of the animals while they explored the same environment in which, however, they faced changes that either altered or did not alter the topological structure of the environment. In experiment 1, closing previously opened doors prevented the rat from having direct access between corresponding sectors. In experiment 2, opening previously closed doors allowed direct access between sectors that had not been directly accessible. In each experiment, control doors allowed us to discard the mere influence of door manipulation. We compared the rats’ exploratory behavior in response to door manipulations that either strongly altered or did not alter the ability to commute between sectors and found evidence that the animals displayed differential reactions to the two types of door manipulations. This implies that during exploration rats build a precise map of the connectivity of space that can be flexibly updated and used for efficient navigation.
TL;DR: Data demonstrate that neonatal piglets can be tested in a spatial T-maze task to assess hippocampal-dependent learning and memory.
Abstract: Pigs are a valuable animal model for studying neurodevelopment in humans due to similarities in brain structure and growth. The development and validation of behavioral tests to assess learning and memory in neonatal piglets are needed. The present study evaluated the capability of 2-week old piglets to acquire a novel place and direction learning spatial T-maze task. Validity of the task was assessed by the administration of scopolamine, an anti-cholinergic drug that acts on the hippocampus and other related structures, to impair spatial memory. During acquisition, piglets were trained to locate a milk reward in a constant place in space, as well as direction (east or west), in a plus-shaped maze using extra-maze visual cues. Following acquisition, reward location was reversed and piglets were re-tested to assess learning and working memory. The performance of control piglets in the maze improved over time (P < 0.0001), reaching performance criterion (80 % correct) on day 5 of acquisition. Correct choices decreased in the reversal phase (P < 0.0001), but improved over time. In a separate study, piglets were injected daily with either phosphate-buffered saline (PBS; control) or scopolamine prior to testing. Piglets administered scopolamine showed impaired performance in the maze compared to controls (P = 0.03), failing to reach performance criterion after 6 days of acquisition testing. Collectively, these data demonstrate that neonatal piglets can be tested in a spatial T-maze task to assess hippocampal-dependent learning and memory.
TL;DR: Capuchin monkeys inhibited the prepotent response to grab food by not reaching out to take less-preferred foods or smaller amounts of food that passed directly in front of them first, confirming that the mechanisms necessary for self-control are present in capuchin monkeys.
Abstract: Self-control is defined as foregoing an immediate reward to gain a larger delayed reward. Methods used to test self-control comparatively include inter-temporal choice tasks, delay of gratification tasks, and accumulation tasks. To date, capuchin monkeys have shown different levels of self-control across tasks. This study introduced a new task that could be used comparatively to measure self-control in an intuitive context that involved responses that required no explicit training. Capuchin monkeys (Cebus apella) were given a choice between two food items that were presented on a mechanized, revolving tray that moved those foods sequentially toward the monkeys. A monkey could grab the first item or wait for the second, but was only allowed one item. Most monkeys in the study waited for a more highly preferred food item or a larger amount of the same food item when those came later, and they inhibited the prepotent response to grab food by not reaching out to take less-preferred foods or smaller amounts of food that passed directly in front of them first. These data confirm that the mechanisms necessary for self-control are present in capuchin monkeys and indicate that the methodology can be useful for broader comparative assessments of self-control.