Volitional control of vocalizations in corvid songbirds.

Songbirds are renowned for their acoustically elaborate songs. However, it is unclear whether songbirds can cognitively control their vocal output. Here, we show that crows, songbirds of the corvid family, can be trained to exert control over their vocalizations. In a detection task, three male carrion crows rapidly learned to emit vocalizations in response to a visual cue with no inherent meaning (go trials) and to withhold vocalizations in response to another cue (catch trials). Two of these crows were then trained on a go/nogo task, with the cue colors reversed, in addition to being rewarded for withholding vocalizations to yet another cue (nogo trials). Vocalizations in response to the detection of the go cue were temporally precise and highly reliable in all three crows. Crows also quickly learned to withhold vocal output in nogo trials, showing that vocalizations were not produced by an anticipation of a food reward in correct trials. The results demonstrate that corvids can volitionally control the release and onset of their vocalizations, suggesting that songbird vocalizations are under cognitive control and can be decoupled from affective states.

Comparing the face inversion effect in crows and humans.

Humans show impaired recognition of faces that are presented upside down, a phenomenon termed face inversion effect, which is thought to reflect the special relevance of faces for humans. Here, we investigated whether a phylogenetically distantly related avian species, the carrion crow, with similar socio-cognitive abilities to human and non-human primates, exhibits a face inversion effect. In a delayed matching-to-sample task, two crows had to differentiate profiles of crow faces as well as matched controls, presented both upright and inverted. Because crows can discriminate humans based on their faces, we also assessed the face inversion effect using human faces. Both crows performed better with crow faces than with human faces and performed worse when responding to inverted pictures in general compared to upright pictures. However, neither of the crows showed a face inversion effect. For comparative reasons, the tests were repeated with human subjects. As expected, humans showed a face-specific inversion effect. Therefore, we did not find any evidence that crows-like humans-process faces as a special visual stimulus. Instead, individual recognition in crows may be based on cues other than a conspecific's facial profile, such as their body, or on processing of local features rather than holistic processing.

Postnatal human cytomegalovirus infection in preterm infants has long-term neuropsychological sequelae.

OBJECTIVE: To evaluate whether an early postnatal infection poses a long-term risk for neuropsychological impairment to neonates born very prematurely. STUDY DESIGN: Adolescents born very preterm (n = 42, 11.6-16.2 years, mean = 13.9; 15 girls; 19 with and 23 without an early postnatal human cytomegalovirus [CMV] infection) and typically developing, term born controls (n = 24, 11.3-16.6 years, mean = 13.6; 12 girls) were neuropsychologically assessed with the German version of the Wechsler Intelligence Scale and the Developmental Test for Visual Perception. RESULTS: As expected, the full cohort of adolescents born preterm had significantly lower scores than term born controls on IQ (preterm: mean [SD] = 98.43 [14.83], control: 110.00 [8.10], P = .015) and on visuoperceptive abilities (95.64 [12.87] vs 106.24 [9.95], P = .016). Furthermore, adolescents born preterm with early postnatal CMV infection scored significantly lower than those without this infection regarding overall cognitive abilities (92.67 [14.71] vs 102.75 [13.67], P = .030), but not visuoperceptive abilities (91.22 [10.88] vs 98.96 [13.45], P > .05). CONCLUSIONS: In our small but well-characterized group, our results provide evidence for adverse effects of early postnatal CMV infection on overall cognitive functions in adolescents born preterm. If confirmed, these results support the implementation of preventive measures.

Crows "count" the number of self-generated vocalizations.

Producing a specific number of vocalizations with purpose requires a sophisticated combination of numerical abilities and vocal control. Whether this capacity exists in animals other than humans is yet unknown. We show that crows can flexibly produce variable numbers of one to four vocalizations in response to arbitrary cues associated with numerical values. The acoustic features of the first vocalization of a sequence were predictive of the total number of vocalizations, indicating a planning process. Moreover, the acoustic features of vocal units predicted their order in the sequence and could be used to read out counting errors during vocal production.

Neural correlates of cognitively controlled vocalizations in a corvid songbird.

The neuronal basis of the songbird's song system is well understood. However, little is known about the neuronal correlates of the executive control of songbird vocalizations. Here, we record single-unit activity from the pallial endbrain region "nidopallium caudolaterale" (NCL) of crows that vocalize to the presentation of a visual go-cue but refrain from vocalizing during trials without a go-cue. We find that the preparatory activity of single vocalization-correlated neurons, but also of the entire population of NCL neurons, before vocal onset predicts whether or not the crows will produce an instructed vocalization. Fluctuations in baseline neuronal activity prior to the go-cue influence the premotor activity of such vocalization-correlated neurons and seemingly bias the crows' decision to vocalize. Neuronal response modulation significantly differs between volitional and task-unrelated vocalizations. This suggests that the NCL can take control over the vocal motor network during the production of volitional vocalizations in a corvid songbird.

Crows flexibly apply statistical inferences based on previous experience.

Statistical inference, the ability to use limited information to draw conclusions about the likelihood of an event, is critical for decision-making during uncertainty. The ability to make statistical inferences was thought to be a uniquely human skill requiring verbal instruction and mathematical reasoning.1 However, basic inferences have been demonstrated in both preliterate and pre-numerate individuals,2,3,4,5,6,7 as well as non-human primates.8 More recently, the ability to make statistical inferences has been extended to members outside of the primate lineage in birds.9,10 True statistical inference requires subjects use relative rather than absolute frequency of previously experienced events. Here, we show that crows can relate memorized reward probabilities to infer reward-maximizing decisions. Two crows were trained to associate multiple reward probabilities ranging from 10% to 90% to arbitrary stimuli. When later faced with the choice between various stimulus combinations, crows retrieved the reward probabilities associated with individual stimuli from memory and used them to gain maximum reward. The crows showed behavioral distance and size effects when judging reward values, indicating that the crows represented probabilities as abstract magnitudes. When controlling for absolute reward frequency, crows still made reward-maximizing choices, which is the signature of true statistical inference. Our study provides compelling evidence of decision-making by relative reward frequency in a statistical inference task.

Reporting and interpreting non-significant results in animal cognition research.

How statistically non-significant results are reported and interpreted following null hypothesis significance testing is often criticized. This issue is important for animal cognition research because studies in the field are often underpowered to detect theoretically meaningful effect sizes, i.e., often produce non-significant p-values even when the null hypothesis is incorrect. Thus, we manually extracted and classified how researchers report and interpret non-significant p-values and examined the p-value distribution of these non-significant results across published articles in animal cognition and related fields. We found a large amount of heterogeneity in how researchers report statistically non-significant p-values in the result sections of articles, and how they interpret them in the titles and abstracts. Reporting of the non-significant results as "No Effect" was common in the titles (84%), abstracts (64%), and results sections (41%) of papers, whereas reporting of the results as "Non-Significant" was less common in the titles (0%) and abstracts (26%), but was present in the results (52%). Discussions of effect sizes were rare (<5% of articles). A p-value distribution analysis was consistent with research being performed with low power of statistical tests to detect effect sizes of interest. These findings suggest that researchers in animal cognition should pay close attention to the evidence used to support claims of absence of effects in the literature, and-in their own work-report statistically non-significant results clearly and formally correct, as well as use more formal methods of assessing evidence against theoretical predictions.

Recursive sequence generation in crows.

Recursion, the process of embedding structures within similar structures, is often considered a foundation of symbolic competence and a uniquely human capability. To understand its evolution, we can study the recursive aptitudes of nonhuman animals. We adopted the behavioral protocol of a recent study demonstrating that humans and nonhuman primates grasp recursion. We presented sequences of bracket pair stimuli (e.g., [ ] and { }) to crows who were instructed to peck at training lists. They were then tested on their ability to transfer center-embedded structure to never-before-seen pairings of brackets. We reveal that crows have recursive capacities; they perform on par with children and even outperform macaques. The crows continued to produce recursive sequences after extending to longer and thus deeper embeddings. These results demonstrate that recursive capabilities are not limited to the primate genealogy and may have occurred separately from or before human symbolic competence in different animal taxa.

Socio-ecological correlates of neophobia in corvids.

Behavioral responses to novelty, including fear and subsequent avoidance of novel stimuli, i.e., neophobia, determine how animals interact with their environment. Neophobia aids in navigating risk and impacts on adaptability and survival. There is variation within and between individuals and species; however, lack of large-scale, comparative studies critically limits investigation of the socio-ecological drivers of neophobia. In this study, we tested responses to novel objects and food (alongside familiar food) versus a baseline (familiar food alone) in 10 corvid species (241 subjects) across 10 labs worldwide. There were species differences in the latency to touch familiar food in the novel object and novel food conditions relative to the baseline. Four of seven socio-ecological factors influenced object neophobia: (1) use of urban habitat (versus not), (2) territorial pair versus family group sociality, (3) large versus small maximum flock size, and (4) moderate versus specialized caching (whereas range, hunting live animals, and genus did not), while only maximum flock size influenced food neophobia. We found that, overall, individuals were temporally and contextually repeatable (i.e., consistent) in their novelty responses in all conditions, indicating neophobia is a stable behavioral trait. With this study, we have established a network of corvid researchers, demonstrating potential for further collaboration to explore the evolution of cognition in corvids and other bird species. These novel findings enable us, for the first time in corvids, to identify the socio-ecological correlates of neophobia and grant insight into specific elements that drive higher neophobic responses in this avian family group. VIDEO ABSTRACT.

Parting self from others: Individual and self-recognition in birds.

Individual recognition is the ability to differentiate between conspecifics based on their individual features. It forms the basis of many complex communicative and social behaviours. Here, we review studies investigating individual recognition in the auditory and visual domain in birds. It is well established that auditory signals are used by many birds to discriminate conspecifics. In songbirds, the neuronal structures underpinning auditory recognition are associated with the song system. Individual recognition in the visual domain has mainly been explored in chickens and pigeons, and is less well understood. Currently it is unknown which visual cues birds use to identify conspecifics, and whether they have cortical areas dedicated to processing individual features. Moreover, whether birds can recognise themselves visually, as evidenced by mirror self-recognition, remains controversial. In the auditory domain, the responses of neurons in the song system suggest identification of the bird's own song. The surveyed behavioural and neural findings can provide a framework for more controlled investigations of individual recognition in birds and other species.

Carrion crows (Corvus corone corone) fail the mirror mark test yet again.

The mirror mark test is generally considered to be an indicator of an animal's ability to recognize itself in the mirror. For this test, an animal is confronted with a mirror and has a mark placed where it can see the mark only with the help of the mirror. When the animal extensively touches or interacts with the mark, compared with control conditions, the mirror mark test is passed. Many nonhuman animal species have been tested, but few have succeeded. After magpies and Indian house crows passed, there has been a sustained interest to find out whether other corvids would pass the mirror mark test. Here, we presented 12 carrion crows (Corvus corone corone) with the mirror mark test. There was no significant increase of mark-directed behavior in the mirror mark test, compared with control conditions. We find very few occasions of mark-directed behaviors and have to interpret them in the context of self-directed behavior more generally. In addition, we show that our crows were motivated to interact with a mark when it was visible to them without the aid of a mirror. We conclude that our crows fail the test, and thereby replicate previous studies showing a similar failure in corvids, and crows in particular. Because our study adds to the growing literature of corvids failing the mirror mark test, the issue of mirror self-recognition in these birds remains controversial. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Difficulties when using video playback to investigate social cognition in California scrub-jays (Aphelocoma californica).

Previous research has suggested that videos can be used to experimentally manipulate social stimuli. In the present study, we used the California scrub-jays' cache protection strategies to assess whether video playback can be used to simulate conspecifics in a social context. In both the lab and the field, scrub-jays are known to exhibit a range of behaviours to protect their caches from potential pilferage by a conspecific, for example by hiding food in locations out of the observer's view or by re-caching previously made caches once the observer has left. Here, we presented scrub-jays with videos of a conspecific observer as well as two non-social conditions during a caching period and assessed whether they would cache out of the observer's "view" (Experiment 1) or would re-cache their caches once the observer was no longer present (Experiment 2). In contrast to previous studies using live observers, the scrub-jays' caching and re-caching behaviour was not influenced by whether the observer was present or absent. These findings suggest that there might be limitations in using video playback of social agents to mimic real-life situations when investigating corvid decision making.

Current desires of conspecific observers affect cache-protection strategies in California scrub-jays and Eurasian jays.

Many corvid species accurately remember the locations where they have seen others cache food, allowing them to pilfer these caches efficiently once the cachers have left the scene [1]. To protect their caches, corvids employ a suite of different cache-protection strategies that limit the observers' visual or acoustic access to the cache site [2,3]. In cases where an observer's sensory access cannot be reduced it has been suggested that cachers might be able to minimise the risk of pilfering if they avoid caching food the observer is most motivated to pilfer [4]. In the wild, corvids have been reported to pilfer others' caches as soon as possible after the caching event [5], such that the cacher might benefit from adjusting its caching behaviour according to the observer's current desire. In the current study, observers pilfered according to their current desire: they preferentially pilfered food that they were not sated on. Cachers adjusted their caching behaviour accordingly: they protected their caches by selectively caching food that observers were not motivated to pilfer. The same cache-protection behaviour was found when cachers could not see on which food the observers were sated. Thus, the cachers' ability to respond to the observer's desire might have been driven by the observer's behaviour at the time of caching.

Experimenter expectancy bias does not explain Eurasian jays' (Garrulus glandarius) performance in a desire-state attribution task.

Male Eurasian jays have been found to adjust the type of food they share with their female partner after seeing her eat 1 type of food to satiety. One interpretation of this behavior is that the male encoded the female's decreased desire for the food she was sated on, and adjusted his behavior accordingly. However, in these studies, the male's actions were scored by experimenters who knew on which food the female was sated. Thus, it is possible that the experimenters' expectations (subconsciously) affected their behavior during tests that, in turn, inadvertently could have influenced the males' actions. Here, we repeated the original test with an experimenter who was blind to the food on which the female was sated. This procedure yielded the same results as the original studies: The male shared food with the female that was in line with her current desire. Thus, our results rule out the possibility that the Eurasian jay males' actions in the food sharing task could be explained by the effects of an experimenter expectancy bias. (PsycINFO Database Record