Animal Cognition最新文献

Stress has been shown to both enhance and inhibit learning, which requires memory formation and memory retention. To date, the question of how stress influences learning and memory retention has been especially well studied in rodents and primates. Here, we expand our understanding of how stress influences memory formation and retention across vertebrates using the African cichlid fish, Neolamprologus pulcher. Fish were randomly assigned to either a control group or a stressed treatment group (with repeated chasing) and then trained to learn a foraging task, where they had to first learn to move a single disc off a food tray and then learned to lift a particular-coloured disc to receive the food reward. More unstressed (control) fish learned the final foraging task compared to the stressed fish although we did not detect a difference in the number of trials taken to reach the learning criteria or the number of mistakes between stressed and unstressed fish. Once the fish had learned the foraging task, we tested their memory for the task after 12, 24 and 48 days without reinforcement. We show that approximately 80% of the fish, regardless of treatment, remembered the task after 12 days, and 55% of the fish tested remembered even after 48 days. When we compared across all the memory trials, the stressed fish overall showed more memory compared to the control fish. Our results provide a memory decay curve and show that stress dampened learning while enhancing memory, thus expanding our understanding of fish cognition.

Domestic dogs demonstrate sensitivity to human gaze and attentiveness, but evidence is mixed for their understanding of human knowledge, in the sense of understanding what a person has or has not seen. Here we tested whether pet dogs take a human competitor’s past visual access into account in a 3-choice food competition task. The dogs (N = 22) observed food being hidden under 2 of 3 cups, and witnessed how their human competitor saw only one baiting. When the human chose first, dogs were expected to avoid the cup she had seen baited; when dogs chose first, they were expected to choose randomly between baited cups, or favour the cup both had seen baited. However, the dogs chose randomly between the baited cups, regardless of who had first choice. The dogs did choose the cup only they had seen baited above chance only when the competitor chose first, suggesting a potential preference for this cup only in this situation, but they did not choose this cup more than the cup both had seen. Therefore, the current study provides no clear evidence that pet dogs infer others’ knowledge from past visual access. The combination of cognitive steps required to be successful in this task might have been too demanding for the dogs. Alternatively, the competitive setting used may not be as suitable for domestic dogs as it is for other species. Further research in ecologically relevant settings may clarify the extent and limits of dogs’ understanding of others’ knowledge.

When animals explore a novel environment, they often aggregate in groups rather than staying isolated to reduce the risks of predation. This effect is known as ‘safety in numbers’ and has been widely reported in terrestrial and aquatic species. Jellyfish are often found to be clustered in the same areas in seas and oceans. Here, we asked whether one reason for such behavior might be the tendency to actively join other conspecifics when encountering novel environments. We observed moon jellyfish (Aurelia spp.) in a free-choice test measuring the proportion of time spent near conspecifics when they are inserted into an unfamiliar environment. We found evidence that jellyfish detect the presence of other conspecifics and use this information to actively direct their behavior in a given direction. Contrary to what was expected by the ‘safety in numbers’ effect, moon jellyfish have significantly distanced themselves from their social companions throughout the whole observation period. This result suggests that, although moon jellyfish are commonly observed in large aggregates in nature due to various environmental factors, they may exhibit limited social behavior in unfamiliar environments.

The vocal mimicry exhibited by female Common Cuckoos (Cuculus canorus), specifically their imitation of raptor calls, has been proposed as a strategy to reduce aggression from host species. Although this hypothesis has been challenged by studies using visual models of cuckoos and hawks, playback-only experiments support the idea of vocal mimicry, i.e. that cuckoo (brood parasite) calls may acoustically mimic those of predators. In this study, we tested the responses of the Red-backed Shrike (Lanius collurio), a known host species, to three types of acoustic stimuli: the female cuckoo’s “bubbling call” (which mimics a predator), the call of the Eurasian Sparrowhawk (Accipiter nisus), and a control call from the Eurasian Collared Dove (Streptopelia decaocto). Playback experiments were conducted both on the breeding grounds in Poland and during migration in Cyprus. Our results revealed that while both cuckoo and sparrowhawk calls elicited behavioural responses, these reactions were clearly distinct. Shrikes responded to sparrowhawk calls by hiding, indicative of predator avoidance, whereas cuckoo calls triggered alertness or approach behaviours. Notably, no response to cuckoo calls was observed during migration, outside the breeding context. This seasonal variation, along with the limited defensive response to cuckoo calls, indicates that vocal mimicry in this context may not serve a protective function. Instead, our findings highlight the shrikes’ nuanced ability to discriminate between acoustic stimuli and respond adaptively based on ecological context. These findings challenge the broad applicability of the predator mimicry hypothesis in cuckoos and emphasise the need for further comparative studies involving diverse host species and multimodal (audiovisual) stimuli.

The study of domestication provides a unique opportunity to analyze the effects of natural selection in the attraction towards novelty, because selective pressures on domesticated animals are often greatly diminished or different from their wild counterparts. In this study, we investigated the neophilic levels of three groups of canids differing in their level of contact with human environments both from an evolutionary and ontogenetic perspective: wolves, pack-living dogs, and pet dogs. In order to study their neophilic response, we presented the animals with two objects. The first of these objects was displayed in the animals’ enclosure for several days. After the animals were habituated to this first object, the second one was introduced together with the first one in a shorter test session meant to explore their preferences for either of the objects. We predicted that dogs —and pet dogs in particular— to display higher levels of neophilia, because human-created environments tend to change at a faster pace, and thus, a higher drive to explore these changes would be more beneficial than in a comparably more stable environment. Our results show no apparent differences between the groups in terms of latency to approach the new object, nor in the identity of the object they approached first. Nonetheless, all groups interacted more with the new object during the test phase. Wolves also interacted longer with the object presented in the first phase of the experiment.

Cognitive research in non-human primates is increasingly conducted in zoos, where zoo visitors are likely to be present and observe the testing sessions. Previous zoo research has shown that such presence can modulate cognitive performance in monkeys, but similar investigations on great apes are still lacking. Here, we investigated the influence of the presence and activity level of zoo visitors on eight chimpanzees (Pan troglodytes) while they completed a working memory task with various difficulty levels. We also recorded whether their conspecifics were present or not in the testing area, and their approximate physical distance. We found that the presence and activity level of the visitors had no effect on chimpanzees’ working memory, regardless of the cognitive demands of the task. Similarly, the presence of conspecifics and how far they were from the individual being tested was not found to significantly influence performance either. These non-significant effects were supported by Bayesian analyses giving support for the null hypotheses. These results suggest that zoo-living chimpanzees are not distracted by visitors when completing a cognitive task. We suggest new directions to further explore social presence effects in great apes.

Equine cognition is relevant to the many roles that horses serve in society, such as leisure riding, competitions, or even animal-assisted therapy. Equine cognitive abilities have been explored in recent years. However, gaining an overview of horse cognition is challenging due to the broad range of abilities studied and the diverse methodologies employed. In addition, the subjects of existing equine cognition studies vary greatly in contextual factors such as their breed, age, sex, and management conditions – each of which may influence test performance in the following cognitive categories: Discrimination Learning; Learning Sets, Categorisation and Concept Formation; Spatial Cognition; Social Learning; and Memory. The aims of this review were (1) to establish whether contextual information was provided in research articles on horse cognition, (2) to tabulate information on the characteristics, housing, and management of subjects used in different categories of cognitive test, (3) to provide an overview of cognitive abilities demonstrated by horses, i.e., the results obtained in cognitive tests, with a specific emphasis on the contextual factors shaping them. The results of this review highlighted important points for future research. Better reporting of subject characteristics in scientific publications would enable investigation of the factors which shape horses’ cognitive abilities, and the use of standardized methods and procedures across studies would facilitate future comparative work.

In stable social environments, the ability to recognise other group members and integrate individual cues with previous experience is likely to be beneficial in mediating social interactions. Under these conditions, selection for individual discrimination and learning of conspecific vocalisations is expected. Recognition may be particularly important in structured societies in which individuals form enduring pair bonds and coordinate biparental care. Many corvids, famed for their sophisticated cognitive abilities, form long-term pair bonds and are considered ideal subjects for investigating the cognitive mechanisms associated with pair bonding; however, evidence that corvids individually recognise their partner under natural conditions remains limited. Here, we tested whether wild jackdaws (Corvus monedula), a colonial corvid, discriminate between the contact calls of individual conspecifics. Incubating females were presented with contact call playbacks from their long-term breeding partner, a male from a neighbouring nest, and an unfamiliar male. Females were quicker to respond to the calls of their partner, providing evidence of mate recognition in corvids in the wild.

Due to their complex social systems and remarkable cognitive abilities, corvids are interesting candidates for large scale comparative research on the meaning of animal calls. However, research on corvid communication has primarily focused on individual signatures or mimicry capabilities, and investigations into the meaning of their calls have yielded comparatively fewer results. This discrepancy can be attributed to several challenges faced by researchers, including difficulties in identifying the units that convey meaning, accurately determining the specific context associated with a call, and the limitations of traditional playback methods when applied to species with extensive repertoires and considerable flexibility in call sequences. In this review, we outline a series of emerging research avenues—recently explored in other songbirds and mammals—that may prove valuable for researchers seeking to understand the meaning behind corvid call sequences. We specifically address the various approaches to identify meaning-bearing units; the strategies for refining the definition of ‘context’ in the assessment of corvids’ repertoires; and the novel protocols and methods that offer alternative perspectives on meaning, beyond the classical playback experimental approaches that were historically used to assess the meaning of calls or call sequences.

Studying Theory of Mind in non-verbal populations requires designing tasks that address the distinction between responding based on directly perceivable cues and additionally inferring others’ mental states. We designed and pre-registered an auditory version of a non-verbal change-of-location task, to investigate whether dogs are sensitive to a human communicator’s mental states about the location of food. With control conditions we ruled out alternative cognitive processes such as associative learning. Dogs (N = 240) could witness that food was hidden first in one opaque bucket (A) and then relocated to a second opaque bucket (B) by an experimenter. Before being allowed to retrieve the food from one of the buckets, dogs received a misleading suggestion (A) from the communicator, who could not see the scene. In all conditions, the communicator could hear food being hidden in A, due to the presence of bells on the lid of this bucket. We manipulated whether she could also hear that food was removed from A and relocated to B (true belief) or not (silent bells on B, leading to her false belief). Importantly, in both conditions the communicator behaved identically (present in the room, suggesting A). Dogs’ responses were not statistically different from those of a previous study using a similar change-of-location task in the visual domain (Lonardo et al. 288(1955), 2021, https://doi.org/10.1098/rspb.2021.0906). Dogs’ choices in the present study, however, did not differ significantly across conditions, suggesting that any auditory perspective-taking ability they might possess did not have a sufficiently large effect to be detected in this study.