Newborns' sensitivity to the visual aspects of infant-directed speech: Evidence from point-line displays of talking faces.

The first time a newborn is held, he is attracted by the human's face. A talking face is even more captivating, as it is the first time he or she hears and sees another human talking. Older infants are relatively good at detecting the relationship between images and sounds when someone is addressing to them, but it is unclear whether this ability is dependent on experience or not. Using an intermodal matching procedure, we presented newborns with 2 silent point-line displays representing the same face uttering different sentences while they were hearing a vocal-only utterance that matched 1 of the 2 stimuli. Nearly all of the newborns looked longer at the matching point-line face than at the mismatching 1, with prior exposure to the stimuli (Experiment 1) or without (Experiment 2). These results are interpreted in terms of newborns' ability to extract common visual and auditory information of continuous speech events despite a short experience with talking faces. The implications are discussed in the light of the language processing and acquisition literature. (PsycINFO Database Record

OB3D, a new set of 3D objects available for research: a web-based study.

Studying object recognition is central to fundamental and clinical research on cognitive functions but suffers from the limitations of the available sets that cannot always be modified and adapted to meet the specific goals of each study. We here present a new set of 3D scans of real objects available on-line as ASCII files, OB3D. These files are lists of dots, each defined by a triplet of spatial coordinates and their normal that allow simple and highly versatile transformations and adaptations. We performed a web-based experiment to evaluate the minimal number of dots required for the denomination and categorization of these objects, thus providing a reference threshold. We further analyze several other variables derived from this data set, such as the correlations with object complexity. This new stimulus set, which was found to activate the Lower Occipital Complex (LOC) in another study, may be of interest for studies of cognitive functions in healthy participants and patients with cognitive impairments, including visual perception, language, memory, etc.

A unified comparison of stimulus-driven, endogenous mandatory and 'free choice' saccades.

It has been claimed that saccades arising from the three saccade triggering modes-stimulus-driven, endogenous mandatory and 'free choice'-are driven by distinct mechanisms. We tested this claim by instructing observers to saccade from a white or black fixation disc to a same polarity (white or black) disc flashed for 100 or 200 ms presented either alone (Exo), or together with an opposite (Endo) or same (EndoFC) polarity disc (blocked and mixed sessions). Target(s) and distractor were presented at three inter-stimulus intervals (ISIs) relative to the fixation offset (ISI: -200, 0, +200 ms) and were displayed at random locations within a 4°-to-6° eccentricity range. The statistical analysis showed a global saccade triggering mode effect on saccade reaction times (SRTs) with Endo and EndoFC SRTs longer by about 27 ms than Exo-triggered ones but no effect for the Endo-EndoFC comparison. SRTs depended on both ISI (the "gap-effect"), and target duration. Bimodal best fits of the SRT-distributions were found in 65% of cases with their count not different across the three triggering modes. Percentages of saccades in the 'fast' and 'slow' ranges of bimodal fits did not depend on the triggering modes either. Bimodality tests failed to assert a significant difference between these modes. An analysis of the timing of a putative inhibition by the distractor (Endo) or by the duplicated target (EndoFC) yielded no significant difference between Endo and EndoFC saccades but showed a significant shortening with ISI similar to the SRT shortening suggesting that the distractor-target mutual inhibition is itself inhibited by 'fixation' neurons. While other experimental paradigms may well sustain claims of distinct mechanisms subtending the three saccade triggering modes, as here defined reflexive and voluntary saccades appear to differ primarily in the effectiveness with which inhibitory processes slow down the initial fast rise of the saccade triggering signal.

Handedness for grasping objects and declarative pointing: a longitudinal study.

It is still unclear whether infants become right-handed because of their left-hemisphere specialization for language (through gestural communication for instance), whether they speak predominantly with their left hemisphere because of this hemisphere's superiority in controlling sequential actions which first results in right-handedness, or whether the two lateralization processes develop independently. To tackle this question, we followed 26 human infants from 8 to 20 months to evaluate the temporal relationship between the emergence of hand preference for grasping objects and for declarative pointing (communicative gesture). Our results show that when grasping and pointing are compared in similar conditions, with objects presented in several spatial positions, the tendency to use the right hand is significantly larger for pointing than for grasping, and both hand preferences are loosely correlated. This suggests that, at least at the age studied here, hand preferences for grasping and for declarative pointing develop relatively independently.

Introspecting on the Timing of One's Actions in a Visuo-Motor Synchronization Task.

By means of a new visuo-motor synchronization paradigm we test the frequently made proposition that one's feeling of having voluntarily made a decision to act is in fact postdictively established contingent on the outcome of his action rather than on its aim. Subjects had to (1) synchronize a key-press with the end of a random synchronization interval (SI) shorter or longer than their reaction time (RT) and (2) judge thereafter whether (Q1) SI had been long enough to allow synchronization, (Q2) their motor response had been "reactive" (i.e., close to their RT) or delayed, or (Q3) whether SI was short or long. SI was denoted by the filling-up time of an annular "gauge." In principle, the "synchronization" key-press should be reactive for SI ≤ RT and delayed in proportion with SI for SI > RT. Instead, response time distributions were bimodal for the shortest (0 ms) and longest (500 ms) SIs and widely spread for intermediate SIs. To all three questions asked, subjects' responses strongly correlated with SI itself (r = 0.62-0.76) and barely with their actual response times (r = 0.03-0.42). Hence subjects' introspective judgments on their trial-by-trial potential capability to synchronize their motor response (Q1) and on their reactive vs. delayed response mode reflected the objective cause of their action rather than being "corrupted" by its outcome (namely their actual response time). That subjects could not reliably decide whether their motor response was reactive or delayed implies that they did not have retrospective access to (or did not remember) their motor decisions which amounts to say that they could not decide on the intentionality of their actions.