Animal Cognition最新文献

Acoustic communication in obligate brood parasitic common cuckoos (Cuculus canorus) plays an important role both in social contacts within its own and with other species (including its many hosts). For example, the female cuckoo’s bubbling call putatively mimics the call of the Eurasian sparrowhawk (Accipiter nisus) to serve as defence from host songbirds mobbing the parasitic female. However, several other, both raptorial and harmless, sympatric bird species also have similar vocalizations to the bubbling call (including the Eurasian kestrel, Falco tinnunculus, and the Eurasian green woodpecker, Picus viridis). Bubbling calls are also used by female cuckoos for conspecific communication with male conspecifics and so the discrimination of acoustically similar con- vs. heterospecific calls should be functionally relevant for cuckoos. We expanded upon a published playback study with all the above species’ calls presented to male cuckoos. The subjects approached the speaker in 100% when conspecific females’ bubbling calls were played back, but rarely (6–12%) did so when either acoustically similar natural calls of sympatric species were used. However, as structurally the bubbling call has no harmonic overtones, but the calls of the other species contain them, we also conducted playbacks with manipulated sound files where the harmonics were removed. Harmonic-free heterospecific calls attracted male cuckoos more often (40–50%) than natural heterospecific calls but still less so than the natural conspecific call. These results reveal the functional importance of the presence of harmonical overtones in heterospecific calls as they can serve to reduce perceptual auditory errors in male cuckoos.

Food-hoarding birds hide many different food types, and are able to remember which kind of food they have hidden and where it was located. Usually, these different food types, although potentially of different value to the birds, are all palatable and would be consumed when encountered. We report on the responses of coal tits (Periparus ater) to peanut pieces that were made distasteful with quinine. While birds preferred eating normal peanut pieces over quinine-soaked ones, they were still very likely to hoard the distasteful nuts. Birds also did not distinguish between the two nut types when retrieving them after 30 min. These findings point towards the compulsive and automatic nature of hoarding decision, independent of the value of the food being hoarded. We discuss how high hoarding motivation may interact with eating motivation to drive natural patterns of hoarding intensity in the field. Our findings also suggest that the taste of hoarded food items is not part of the representation of the cache memory. We speculate that this may be because tasting the item and caching the item happens in separate locations and are therefore not associated with each other.

Working memory (WM), an attention-based short-term storage system responsible for the manipulation and integration of past knowledge with present information for goal-directed behavior, is a key executive function and a principal predictor of general intelligence. Despite its importance, WM has not been a major research topic in animal behavior. Here, we first summarize key ideas related to WM from the social sciences for interested colleagues. Given that past methodological inconsistencies have led to mixed results and conclusions across various species, we then designed experiments that incorporate the critical components of WM, facilitating cross-species comparisons and accounting for potential ecological influences. We present such experiments on WM in an ectothermic vertebrate, the cleaner wrasse (Labroides dimidiatus), which faces environmental challenges potentially requiring complex cognitive adaptations. Overcoming several experimental challenges, we consistently obtained negative results across multiple experimental paradigms. As our experiments were specifically designed to test WM, our negative results call into question previous studies in other fish species that provide evidence for WM using different paradigms. More specific tests for WM should be developed to confirm the presence or absence of this executive function in other ectotherm vertebrates. The absence of WM may be a key factor underlying the significant encephalization gap between ectotherm and endotherm vertebrate species.

When faced with a predator, parent birds have to choose between current and future breeding. Previous studies have shown that the body condition and personality of parents influence the trade-offs. However, whether body condition and personality influence an individual’s nest defense behavior has rarely been investigated. Here, we studied whether body condition and personality affect the nest defense behavior of incubating Japanese tits (Parus minor). Some females exhibited intense nest defense behavior when human-simulated intruders approached. Notably, individuals exhibiting high nest defense behavior had significantly shorter tail lengths compared to individuals who did not. In addition, bold individuals would exhibit higher nest defense behavior than those showing low defense responses. Furthermore, bold individuals consistently demonstrated stronger nest defense behavior compared to shy individuals, aligning with their proactive personality traits. This pattern highlights the potential role of individual behavioral differences in shaping anti-predator strategies.

Animals may benefit from the ability to discriminate between quantities in their environment; for example, when choosing between foraging patches differing in food availability or assessing the size of rival groups. Numerous studies utilising spontaneous quantity discrimination tasks have found that a wide range of species possess the ability to discriminate between quantities, with large interspecific differences being found in these capabilities. However, the causes of variation in quantity discrimination have received less attention, particularly when considering intraspecific variation. Here, we use a spontaneous quantity discrimination task to (i) investigate if Western Australian magpies possess quantity discrimination abilities, and (ii) determine the factors that underlie individual variation in this ability. We found that magpies were able to discriminate between two discrete quantities of a food reward and chose the larger quantity of food more often than expected by chance, with their accuracy increasing as the difference between the two quantities of food items increased (i.e. as the ratio decreased). Individual performance on the assay was significantly affected by group size, with individuals from smaller groups choosing the larger quantity of food more often than individuals from larger groups when presented with the 2 vs. 5 combination. This group size difference may arise because individuals from smaller groups benefit more from enhanced quantity discrimination abilities compared to individuals from larger groups due to the greater risk of competition and loss of resources from intergroup conflict with larger groups. Our study is the first to investigate and identify group size as a source of intraspecific variation in spontaneous quantity discrimination abilities and highlights the importance of considering the causes of individual variation in cognitive performance.

When animals use the same route repeatedly, they have the opportunity to update information that might help them to navigate more quickly and more accurately. Here we analyse ants involved in tandem running, in which the leader has evaluated a new nest and decided to recruit to it while the follower has chosen to be led and shown the route. We used a motorised gantry equipped with a camera to track the movements of tandem members on their tandem and return trips in a landmark-rich and a landmark-poor environment. Although the amount of visual navigational information did not affect the movements of leaders or followers on their tandem trip, the paths of followers were significantly more tortuous and their speeds significantly slower than those of leaders on their return trips in the landmark-poor environment. By contrast, there were no such differences between the followers and leaders on their return trips in the landmark-rich environment even though the return paths of followers in the landmark-rich environment were significantly more tortuous than that of leaders in the landmark-poor environment. Indeed, in the landmark-rich environment, the majority of the leaders’ return paths had loops while most were straight in the landmark-poor environment. Thus, the availability of more information when many landmarks are present may induce tandem leaders to make the loops, typically associated with the paths of tandem followers. This suggests knowledgeable individuals slow down to update navigational information and has implications for the formation of leader oligarchies in tandem running.

While spoken language is unique to humans, many features of human communication are shared with great apes, including the use of signals in multiple modalities such as vocalizations, gestures, and facial expressions. Communication signals can be unimodal (involving a single modality) or multimodal (combining multiple modalities simultaneously). Here, we examined age-related differences in bonobo (Pan paniscus) unimodal and multimodal communication signals. We assessed all vocalizations, gestures, facial expressions, and multimodal combinations produced by captive bonobos across a variety of behavioral contexts. All occurrences of communication signals were collected via focal observations from 12 individuals ranging from 6 months to 44 years of age. All individuals produced multimodal communication signals but all bonobos, regardless of age, produced multimodal signals at lower frequencies than unimodal signals. Age had a significant effect with younger bonobos producing more multimodal signals than older individuals (p < 0.001). The infant and juveniles produced the most multimodal signals and there was an approximately 6% increase in unimodal signals per age year increase. These findings indicate a developmental shift toward unimodal signals as bonobos age. Behavioral context was predictive of signal type usage with an increase of multimodal signals in agonistic (p < 0.001), play (p < 0.001), and sexual contexts (p = 0.001). This indicates that context is important for bonobo modality with multimodal signaling occurring more in “high-risk/high-reward” contexts where proper signal comprehension is vital. This study represents an overview of multimodal communication across bonobo life stages, offering further insights into primate communication patterns and developmental trajectories.

As representatives of a basal bird lineage, pigeons have exhibited remarkable visual numerical cognition, comparable even to that of monkeys. Nevertheless, whether visual numerical cognition in pigeons conforms to the Weber–Fechner law remains unknown. To address this, we designed a fully automated apparatus tailored for pigeons and used it to train them to perform a delayed match-to-numerosity task. The results showed that on a linear scale, pigeons represented smaller numerosities with higher precision and larger numerosities with lower precision, exhibiting a numerical magnitude effect. When the linear scale was compressed into a logarithmic scale, this magnitude effect was offset, resulting in similar representational characteristics across different numerosities. This finding suggests that the mental number line of pigeons is logarithmic rather than linear, consistent with the Weber–Fechner law. While biological brains seek precision in representing numerical information, they must also take computational load into account. This representational strategy may be the optimal outcome of the trade-off between computational precision and computational load that biological brains have achieved through long-term evolution.

Metacognition– namely the capacity to reflect on one’s own cognitive processes - provides animals with numerous evolutionary advantages. Metacognition abilities encompass enhanced decision-making in uncertain situations, more efficient resource management, error detection and correction, and improved problem-solving skills. Here, we investigate how Eurasian jays, Garrulus glandarius, monitor uncertainty through a working memory food-retrieval task. In this task, a desirable food item is hidden under one of two cups, which are then shuffled either once (easy treatment) or several times (difficult treatment). The jays then choose to either engage in locating the food or opt out by selecting a third cup that offers a less preferred food reward. Our findings reveal that the difficulty of the task significantly influenced the jays’ choice, with a higher tendency to opt out during difficult trials. Individual performance analysis revealed that when jays that typically opted out of difficult trials chose to engage instead, they exhibited significant accuracy. This suggests their decisions were guided by a confidence assessment of their knowledge. Overall, our study indicates that Eurasian jays possess metacognitive abilities that enable them to evaluate their own certainty and make strategic decisions based on perceived task difficulty and confidence in their knowledge. These capabilities likely confer advantages in natural settings, such as caching behaviours, allowing jays to make well-informed decisions about when to store or retrieve food based on environmental cues and internal assessments of uncertainty.

Scatter hoarding black-capped chickadees use memory to relocate hidden food, often after delays of hours or days. The ability of these birds to maintain accurate memories of the location and current status of many food caches while engaging in other distracting daily activities suggests that their memory may be especially resistant to competing cognitive load. We measured resistance to competing cognitive load during spatial memory tests in black-capped chickadees (Poecile atricapillus) and a non-caching species, dark-eyed juncos (Junco hyemalis). Birds were presented with two types of task. In the Discrimination task, birds learned by trial-and-error to select a target from among 2 distractors. In the Match-to-Sample task, birds viewed a sample which they had to remember in order to correctly select it from among two distractors at test. On two-thirds of trials, the tasks were presented Stand-Alone: after birds initiated a trial, they completed either a Discrimination or a Match-to-Sample task. The remaining trials were Concurrent causing a competing cognitive load: after birds intiated a trial, they saw the sample for the Match-to-Sample task, then completed a Discrimination during the retention interval, and finally completed a Match-to-Sample test. Competing cognitive load reduced accuracy of juncos significantly more than accuracy of chickadees. The need to encode and retain the locations of multiple food caches may have led to the evolution of enhanced cognitive control of memory in black-capped chickadees.