4 décembre 2012
Brent Strickland: "Core knowledge operates automatically and tacitly in adults: Three case studies"
"Core cognition" is typically studied in the context of infancy research on early emerging physical or social knowledge (Spelke & Kinzler, 2007) . This work emphasizes the bootstrapping function that innate knowledge serves in guiding early learning. However, core cognition also continues to operate automatically and often tacitly into adulthood and in ways that can be at odds with other aspects of adult cognition. This phenomenon was originally discovered by vision researchers interested in the overlap between infant object knowledge and the visual system's representations of objects (Scholl, 2001). Here I present three new lines of research demonstrating that core cognition's influence on the adult mind is much more pervasive than originally thought. First, the adult visual system automatically categorizes physical events into discrete types (e.g. containment, occlusion, covering, etc..) and uses these representations to guide attention in a way that directly mirrors recently observed results in infants. Secondly, just as pre-verbal infants appear to automatically infer the presence of unseen causes in collision events, so too can such inferences cause adults to falsely remember having seen a (visually absent but implied) collision. Finally, the concept of a social "agent," which guides young infants' expectations about the behavior of social (as compared to inanimate) actors, is also deeply embedded in the structure of natural language processing in adulthood. Taken as a whole, these findings suggest that core knowledge structures the on-line operation of a wide range of adult mental faculties such as language, memory, and perception. A major future challenge is to better understand the ways in which these "infant legacies" both facilitate and distort adult cognition.
27 novembre 2012
De 12h à 13h30, salle Langevin, 29 rue d'Ulm.
Ted Gibson: "Language for communication: Language comprehension and the communicative basis of word order"
Perhaps the most obvious hypothesis for the function of human language is for use in communication. Chomsky has famously argued that this is a flawed hypothesis, because of the existence of such phenomena as ambiguity. Furthermore, he argues that the kinds of things that people tend to say are not short and simple, as would be predicted by communication theory. Contrary to Chomsky, my group applies information theory and communication theory from Shannon (1948) in order to attempt to explain the typical usage of language in comprehension and production, together with the structure of languages themselves. First, we show that ambiguity out of context is not only not a problem for an information-theoretic approach to language, it is a feature. Second, we show that language comprehension appears to function as a noisy channel process, in line with communication theory. Given si, the intended sentence, and sp, the perceived sentence we propose that people maximize P(si | sp ), which is equivalent to maximizing the product of the prior P(si) and the likely noise processes P(si â†’ sp ). We show that several predictions of this way of thinking of language are true: (1) the more noise that is needed to edit from one alternative to another leads to lower likelihood that the alternative will be considered; (2) in the noise process, deletions are more likely than insertions; (3) increasing the noise increases the reliance on the prior (semantics); and (4) increasing the likelihood of implausible events decreases the reliance on the prior. Third, we show that this way of thinking about language leads to a simple re-thinking of the P600 from the ERP literature. The P600 wave was originally proposed to be due to people's sensitivity to syntactic violations, but there have been many instances of problematic data in the literature for this interpretation. We show that the P600 can best be interpreted as sensitivity to an edit in the signal, in order to make it more easily interpretable. Finally, we discuss how thinking of language as communication can explain aspects of the origin of word order. Some recent evidence suggests that subject-object-verb (SOV) may be the default word order for human language. For example, SOV is the preferred word order in a task where participants gesture event meanings (Goldin-Meadow et al. 2008). Critically, SOV gesture production occurs not only for speakers of SOV languages, but also for speakers of SVO languages, such as English, Chinese, Spanish (Goldin-Meadow et al. 2008) and Italian (Langus & Nespor, 2010). The gesture-production task therefore plausibly reflects default word order independent of native language. However, this leaves open the question of why there are so many SVO languages (41.2% of languages; Dryer, 2005). We propose that the high percentage of SVO languages cross-linguistically is due to communication pressures over a noisy channel. We provide several gesture experiments consistent with this hypothesis, and we speculate how a noisy channel approach might explain several typical word order patterns that occur in the world's languages.
20 novembre 2012
De 12h à 13h30, salle Langevin, 29 rue d'Ulm, 75005 Paris
Ryota Kanai, University of Sussex & UCL Institute of Cognitive Neuroscience: «Brain structure approach to visual awareness and attention in everyday life ».
We all appreciate substantial differences among our friends and colleagues in their cognitive ability and style. Such variability introduces a rich diversity of culture and lifestyle into our society. Importantly, individual differences can be used as a source of information that links brain structure to cognitive functions, functional differences of a brain region across individuals can be detected as systematic variation of regional gray matter volume and white matter microstructure using voxel-based morphometry (VBM) and diffusion tensor imaging (DTI), respectively (Kanai & Rees 2011). In this talk, I will show how this approach can be applied to identify the brain structure that determines the dynamics of perceptual rivalry. Our VBM and DTI results show that anterior and posterior parts of intraparietal sulcus (IPS) play distinct roles in perceptual rivalry. VBM shows that individuals with fast switch rate exhibited greater gray matter volume in posterior IPS, whereas slow switchers had greater anterior IPS. Fractional anisotropy (FA) values derived from DTI show that the white matter integrity beneath these regions correlated with perceptual switch rate. We complemented the correlational nature of these analyses by confirmatory TMS experiments and thereby established causal involvement of these regions in perceptual rivalry. These results together suggest that perceptual rivalry reflects a balance between top-down sustention of a current percept by anterior IPS and monitoring of possibly conflicting sensory evidence by posterior IPS. Finally, I will discuss the application of this approach in real life situations. In contrast to functional neuroimaging, structural neuroimaging does not require a virtual environment that emulates cognitive and social tasks motivated by real life situations. Instead, brain structure information can be directly linked to behaviors observed in real life. I will provide a few examples in which variability in brain structure has been linked to everyday behaviors such as attentional distractibility, loneliness and online social networks. This opens a new possibility to investigate brain functions from the perspective of everyday behavioral data by introducing fieldwork to cognitive neuroscience.
13 novembre 2012
De 12h à 13h30, salle Langevin, 29 rue d'Ulm.
Michel Thiebaut de Schotten: "A fronto parietal network for spatial Awareness"
Looking for a friend in the crowd or avoiding a sudden danger are two actions based on the quality of our visuo-spatial attention. Behavioural tests and brain imaging technology demonstrated that visuo-spatial attention is a specialized function of the right hemisphere of the brain. However, anatomical features supporting this specialization have remained elusive. We scanned volunteers with a novel brain imaging technology that can depict the white matter connections, and we measured the degree of specialization of the right hemisphere for visuo-spatial attention with behavioural tests. Exploring the brain circuits, we found white matter connections whose size predicts the degree of specialization of the right hemisphere for visuo-spatial attention. Whilst a damage of this connection in the right hemisphere can predict chronicity of the visuospatial deficits, the lateralisation of this same connection may be predictive of visuo-spatial recovery.
6 novembre 2012
De 12h à 13h30, salle Langevin, 29 rue d'Ulm, 75005 Paris
Franck Ramus: « General intelligence : myth or reality ? »
The notion of general intelligence arises from the observation that performance across a large array of cognitive tests is correlated, such that a factor analysis yields one factor explaining a substantial part of the variance. This statistical observation has led Spearman (1904) to postulate that a single biological or psychological property ("g" for general intelligence) underlies the performance in all intelligence tests and subtests. Although this hypothesis has been debated for a whole century, it has become widely accepted, both within intelligence research and in related fields. For instance, it underlies brain imaging studies on "the neural basis of intelligence" as well as (largely unsuccessful) attempts to find genes associated with general intelligence. Yet it has become increasingly clear in recent years that there is no such thing as general intelligenceroscience.
23 octobre 2012
De 12h à 13h30, salle Langevin
Jean-Baptiste André (Biologie, ENS): "The evolution of mutual benefits and fairness. Why are humans special?"
The evolutionary foundations of fairness is one of the most hotly debated questions in evolutionary anthropology. Reciprocate cooperation (in a large sense) generates collective benefits and, beyond explaining its mere existence, it is also essential to understand how evolution has shaped the way these benefits are divided. Fairness is the fact that, among the many ways to distribute collective benefits, we tend to favor impartial distributions and request our partners to do the same (e.g. 50/50 divisions in symmetric interactions). The evolution of fairness raises a particularly difficult question for theoreticians, as it actually entails dealing with the so-called issue of “equilibrium selection”. The principle of reciprocity per se is underdetermined (this is known in game theory as the “folk theorem”), which fundamentally stems from the fact that a very wide range of cooperative agreements are better than being alone. Influential authors have thus claimed that this problem is actually so difficult that it requires, almost unavoidably, the operation of some form of group selection . Here, we offer an alternative solution. We show that the indeterminacy of reciprocate cooperation vanishes if one considers properly the outside options of individuals. In reality, the question is not whether a given interaction is better than being alone, but whether a given interaction is better than another interaction, possibly with a different partner [2,3]. We will present an overview of our modeling results in this field [4,5], together with the results of a model built specially to deal with the issue of equilibrium selection. We show that fairness evolves naturally when individuals have varied social opportunities, because the issue of each interaction is then constrained by the fact that it must bring at least the same benefit than other interactions. In particular, if two individuals have the same outside opportunities, they can agree upon an interaction only if it brings the same benefit to both of them. The indeterminacy of reciprocity is hence in large part an artifactual consequence of the way models are usually built, and the evolution of fairness does not require any form of group selection.