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

Apprentissage de dépendances non-adjacentes et traitement de grammaires supra-régulières chez le babouin et l'humain

A current dominant hypothesis on the evolution of syntactic abilities propose that the processing of supra-regular grammars is a unique human capacity. In support of this hypothesis, artificial grammar learning studies conducted so far do not provide unambiguous demonstration of this capacity in a non-human species. In this thesis, we adopted a new approach by studying cognitive prerequisites for supra-regular grammar processing. Our hypothesis was that these previous failures could be attributed to a bias in these species towards the exploitation of local regularities and difficulties for processing more distant relationships, rather than an inability to master supra-regular grammars. We conducted a series of experiments in Guinea baboons (Papio papio) and humans to assess this hypothesis. In a first experiment, we show that baboons need much more exposure than humans to learn non-adjacent associations. In a second study, we show that baboons can generalize patterns involving an adjacent or a non-adjacent repetition of an element, but that they are more sensitive to the former. A third, correlational, study reveal that baboons succeeding to extract non-adjacent regularities are not those showing the best performance in learning local ones. A last study suggest that baboons are sensitive to a mirror structure (involving center-embedded dependencies), but not to a copy structure (crossed dependencies). Overall, our results reveal a stronger continuity in grammar processing capacities within the primate order than previously thought, but also highlight important species differences in memory constraints.Une hypothèse dominant actuellement les théories sur l’évolution des capacités syntaxiques est celle d’une spécificité humaine pour le traitement des grammaires supra-régulières. Cette hypothèse est supportée par les données comparatives actuellement disponibles, qui ne fournissent pas de démonstration non ambiguë de cette capacité chez une autre espèce. Dans cette thèse, nous avons adopté une nouvelle approche consistant à examiner si ces échecs pourraient découler de la difficulté que représente l'extraction de régularités non-adjacentes. Pour tester cette hypothèse, nous avons mené une série de quatre études chez le babouin de guinée (Papio papio) et l’humain. La première étude montre que les babouins requièrent une quantité d’exposition beaucoup plus importante que l’humain pour apprendre des associations non-adjacentes. Dans une seconde étude, les babouins ont pu généraliser des patterns basés sur une répétition adjacente ou non-adjacente d’un élément, mais ils se sont montrés davantage sensibles à ces premiers. Une troisième étude, corrélationnelle, révèle que les babouins se montrant sensibles aux régularités non-adjacentes ne sont pas ceux obtenant les meilleures performances pour l’apprentissage de dépendances adjacentes. Une dernière étude suggère que les babouins sont sensibles à une structure en miroir (impliquant des dépendances centrées-emboitées), mais pas à une structure en copie (à dépendances croisées). Ces résultats mettent au jour une importante continuité des capacités syntaxiques au sein de la lignée des primates, mais révèlent également des différences inter-spécifiques importantes dans les contraintes mnésiques pesant sur celles-ci

Apprentissage de dépendances non-adjacentes et traitement de grammaires supra-régulières chez le babouin et l'humain

A current dominant hypothesis on the evolution of syntactic abilities propose that the processing of supra-regular grammars is a unique human capacity. In support of this hypothesis, artificial grammar learning studies conducted so far do not provide unambiguous demonstration of this capacity in a non-human species. In this thesis, we adopted a new approach by studying cognitive prerequisites for supra-regular grammar processing. Our hypothesis was that these previous failures could be attributed to a bias in these species towards the exploitation of local regularities and difficulties for processing more distant relationships, rather than an inability to master supra-regular grammars. We conducted a series of experiments in Guinea baboons (Papio papio) and humans to assess this hypothesis. In a first experiment, we show that baboons need much more exposure than humans to learn non-adjacent associations. In a second study, we show that baboons can generalize patterns involving an adjacent or a non-adjacent repetition of an element, but that they are more sensitive to the former. A third, correlational, study reveal that baboons succeeding to extract non-adjacent regularities are not those showing the best performance in learning local ones. A last study suggest that baboons are sensitive to a mirror structure (involving center-embedded dependencies), but not to a copy structure (crossed dependencies). Overall, our results reveal a stronger continuity in grammar processing capacities within the primate order than previously thought, but also highlight important species differences in memory constraints.Une hypothèse dominant actuellement les théories sur l’évolution des capacités syntaxiques est celle d’une spécificité humaine pour le traitement des grammaires supra-régulières. Cette hypothèse est supportée par les données comparatives actuellement disponibles, qui ne fournissent pas de démonstration non ambiguë de cette capacité chez une autre espèce. Dans cette thèse, nous avons adopté une nouvelle approche consistant à examiner si ces échecs pourraient découler de la difficulté que représente l'extraction de régularités non-adjacentes. Pour tester cette hypothèse, nous avons mené une série de quatre études chez le babouin de guinée (Papio papio) et l’humain. La première étude montre que les babouins requièrent une quantité d’exposition beaucoup plus importante que l’humain pour apprendre des associations non-adjacentes. Dans une seconde étude, les babouins ont pu généraliser des patterns basés sur une répétition adjacente ou non-adjacente d’un élément, mais ils se sont montrés davantage sensibles à ces premiers. Une troisième étude, corrélationnelle, révèle que les babouins se montrant sensibles aux régularités non-adjacentes ne sont pas ceux obtenant les meilleures performances pour l’apprentissage de dépendances adjacentes. Une dernière étude suggère que les babouins sont sensibles à une structure en miroir (impliquant des dépendances centrées-emboitées), mais pas à une structure en copie (à dépendances croisées). Ces résultats mettent au jour une importante continuité des capacités syntaxiques au sein de la lignée des primates, mais révèlent également des différences inter-spécifiques importantes dans les contraintes mnésiques pesant sur celles-ci

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

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