Corollary Discharge Failure in an Oculomotor Task Is Related to Delusional Ideation in Healthy Individuals

International audiencePredicting the sensory consequences of saccadic eye movements likely plays a crucial role in planning sequences of saccades and in maintaining visual stability despite saccade-caused retinal displacements. Deficits in predictive activity, such as that afforded by a corollary discharge signal, have been reported in patients with schizophrenia, and may lead to the emergence of positive symptoms, in particular delusions of control and auditory hallucinations. We examined whether a measure of delusional thinking in the general, non-clinical population correlated with measures of predictive activity in two oculomotor tasks. The double-step task measured predictive activity in motor control, and the in-flight displacement task measured predictive activity in trans-saccadic visual perception. Forty-one healthy adults performed both tasks and completed a questionnaire to assess delusional thinking. The quantitative measure of predictive activity we obtained correlated with the tendency towards delusional ideation, but only for the motor task, and not the perceptual task: Individuals with higher levels of delusional thinking showed less self-movement information use in the motor task. Variation of the degree of self-generated movement knowledge as a function of the prevalence of delusional ideation in the normal population strongly supports the idea that corollary discharge deficits measured in schizophrenic patients in previous researches are not due to neuroleptic medication. We also propose that this difference in results between the perceptual and the motor tasks may point to a dissociation between corollary discharge for perception and corollary discharge for action

Extraction of structural regularities by baboons (Papio Papio): Adjacent and nonadjacent repetition patterns differ in learnability.

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Sea lions' (Zalophus californianus) use of human pointing gestures as referential cues

International audienceThis experiment investigated the ability of four human-socialized sea lions to exploit human communicative gestures in three different object-choice tasks based on directional cues emitted by their caretakers. In Study 1, three of the tested subjects were able to generalize their choice of the pointed target to variations of the basic pointing gestures (i.e., cross-body point, elbow point, foot point, and gaze only), from the very first trials. Study 2 showed that the subjects could follow the pointing gestures geometrically and select the correct target among four possible targets, two on each side of the informant. In Study 3, we tested the robustness of their tendency to follow a pointing gesture by hiding targets behind barriers. One subject was able to follow pointing gestures towards targets not visible at the moment of their decision without any training, despite the presence of another visible and directly accessible one. Taken together, these results suggest that sea lions were able to use the referential property of the human pointing gesture, because they were able to rely on extrapolating precise linear vectors along different pointing body parts in order to identify a precise object rather than merely a general direction. These findings support previous arguments that some non-domesticated species might have as great an ability to respond appropriately to pointing gestures as domesticated dogs. The potential roles of human-socialization and specific features of wild sea lions ecology are discussed

From Rote Memorization to Structure Extraction: Sequence Learning in Baboons

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Do they know or just do it? Investigating implicit and explicit sequence learning by capuchin monkeys, human adults and children

In humans, it is now established that sequential regularities can be learned implicitly (i.e. without acquiring conscious knowledge) or explicitly (with acquisition of conscious knowledge). Is this dual-processing capability also the case for non-human primates? In this study, we designed a non-verbal task to probe implicit and explicit sequence learning in capuchin monkeys (Sapajus sp., n = 12), human adults (n = 12), and children from 5 to 10 years old (n = 64). After learning spatial sequences on a touchscreen, participants’ conscious access to the sequences was probed with a forced choice sequence completion test. All performed above chance level in this test, without being instructed or trained to do so. However, only human adults who reported the presence of regularities performed at ceiling level. We suggest future directions that could build on our findings to disentangle implicit and explicit learning in monkeys and children

Assessment of metacognitive monitoring and control in baboons (Papio papio)

International audienceMetacognition refers to the ability of an organism to evaluate its states of knowledge (metacognitive monitoring) and engage in appropriate information-seeking behaviors when a lack of knowledge is detected (metacognitive control). This study assessed metacognitive monitoring and control in three Guinea baboons (Papio papio). Monkeys were required to report on a touchscreen the location of two target stimuli that had previously appeared briefly on a grid. They could either respond directly or use a ``Repeat'' key providing an opportunity to repeat the target stimuli. In Experiment 1, the baboons used the Repeat key more frequently in difficult trials and transferred this use of the key to novel conditions. Two baboons showed higher accuracy when they declined using the key compared to Baseline trials in which the key was not available, suggesting accurate metacognitive monitoring judgments. The same two baboons were consistently faster at reporting the targets' locations after a repetition of the stimulus. In Experiment 2, the baboons had to choose between two Repeat keys, one for each target. Two baboons showed a preference for repeating the presentation of the less visible target, suggesting that they identified what information they lack. Overall, results support the hypothesis of metacognitive monitoring in baboons, and also provide limited evidence for metacognitive control. We propose that tests requiring subjects to choose between several metacognitive responses in computerized tasks provide a suitable new approach for studying targeted information-seeking behaviors in animals

Baboons (Papio papio) Process a Context-Free but Not a Context-Sensitive Grammar

International audienceLanguage processing involves the ability to master supra-regular grammars, that go beyond the level of complexity of regular grammars. This ability has been hypothesized to be a uniquely human capacity. Our study probed baboons' capacity to learn two supra-regular grammars of different levels of complexity: a context-free grammar generating sequences following a mirror structure (e.g., AB | BA, ABC | CBA) and a context-sensitive grammar generating sequences following a repeat structure (e.g., AB | AB, ABC | ABC), the latter requiring greater computational power to be processed. Fourteen baboons were tested in a prediction task, requiring them to track a moving target on a touchscreen. In distinct experiments, sequences of target locations followed one of the above two grammars, with rare violations. Baboons showed slower response times when violations occurred in mirror sequences, but did not react to violations in repeat sequences, suggesting that they learned the context-free (mirror) but not the context-sensitive (repeat) grammar. By contrast, humans tested with the same task learned both grammars. These data suggest a difference in sensitivity in baboons between a context-free and a context-sensitive grammar

Métacognition chez le babouin : chercher l'information manquante

Le terme "métacognition" renvoie à la capacité d'un organisme à émettre des jugements sur ses propres connaissances, et à exercer en retour un contrôle sur celles-ci. Longtemps considérés comme l'un des produits les plus sophistiqués de la cognition humaine, les travaux menés en cognition comparée cette dernière décennie ont montré que des animaux non-humains, du pigeon au chimpanzé, étaient capables d'évaluer leur degré d'incertitude dans diverses tâches de catégorisation perceptive et de mémorisation. Dans cette étude, une nouvelle procédure expérimentale a été mise en place pour en étudier les mécanismes sous-jacents : dans une tâche de reproduction de pattern sur écran tactile, une icône a été mise à disposition des sujets, leur permettant de revoir à volonté le pattern à mémoriser avant de le reproduire. Les trois babouins testés ont appris à l'utiliser lorsqu'ils se trouvaient en difficulté, et ont spontanément transféré ce comportement à de nouvelles conditions. Dans une seconde expérience, deux d'entre eux ont appris à choisir entre plusieurs clés pour revoir sélectivement les parties du pattern les plus difficiles à mémoriser. Ces résultats suggèrent que des primates non-humains sont capables non seulement d'une évaluation de leur propre degré d'incertitude, mais également d'identifier précisément la source de cette incertitude, et d'orienter leurs comportements de recherche d'informations en conséquence

Non-adjacent Dependencies Processing in Human and Non-human Primates

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