Publications of Csibra, G.

Teleological reasoning in infancy: the naive theory of rational action

Converging evidence demonstrates that one-year-olds interpret and draw inferences about other's goal-directed actions. We contrast alternative theories about how this early competence relates to our ability to attribute mental states to others. We propose that one-year-olds apply a non-mentalistic interpretational system, the 'teleological stance' to represent actions by relating relevant aspects of reality (action, goal-state and situational constraints) through the principle of rational action, which assumes that actions function to realize goal-states by the most efficient means available. We argue that this early inferential principle is identical to the rationality principle of the mentalistic stance – a representational system that develops later to guide inferences about mental states.

Eye contact detection in humans from birth

Making eye contact is the most powerful mode of establishing a communicative link between humans. During their first year of life, infants learn rapidly that the looking behaviors of others conveys significant information. Two experiments were carried out to demonstrate special sensitivity to direct eye contact from birth. The first experiment tested the ability of 2- to 5-day-old newborns to discriminate between direct and averted gaze. In the second experiment, we measured 4-month-old infants' brain electric activity to assess neural processing of faces when accompanied by direct (as opposed to averted) eye gaze. The results show that, from birth, human infants prefer to look at faces that engage them in mutual gaze and that, from an early age, healthy babies show enhanced neural processing of direct gaze. The exceptionally early sensitivity to mutual gaze demonstrated in these studies is arguably the major foundation for the later development of social skills.

Illusory contour figures are perceived as occluding surfaces by 8-month-old infants

Infants have been demonstrated to be able to perceive illusory contours in Kanizsa figures. This study tested whether they also perceive these illusory figures as having the properties of real objects, such as depth and capability of occluding other objects. Eight- and five-month-old infants were presented with scenes that included a Kanizsa square and further depth cues provided by the deletion and accretion pattern of a moving duck. The 8-month-old infants looked significantly longer at the scene when the two types of occlusion cues were inconsistent than when they were consistent with each other, which provides evidence that they interpreted the Kanizsa square as a depth cue. In contrast, 5-month-olds did not show this difference. This finding demonstrates that 8-month-olds perceive the figure formed by the illusory contours as having properties of a real object that can act as an occluder.

Differential frontal cortex activation before anticipatory and reactive saccades in infants

Neural correlates of anticipatory and reactive saccades were studied in 4-month-old infants by recording high-density event-related potentials. Infants were presented with a fixed sequence of stimulus presentation to which they rapidly showed anticipatory saccades, as well as continuing with some reactive (stimulus-driven) saccades. As in a previous study, no clear evidence was found for adultlike, saccade-related potentials, although some presaccadic differences between reactive and anticipatory saccades were observed. Infants also showed different stimulus offset-related effects preceding the 2 types of trials with a right-frontal positivity when an anticipatory look follows, but only left-frontal positivity when a reactive saccade follows.

Disordered visual processing and oscillatory brain activity in autism and Williams Syndrome

Two developmental disorders, autism and Williams syndrome, are both commonly described as having difficulties in integrating perceptual features, i.e. binding spatially separate elements into a whole. It is already known that healthy adults and infants display electroencephalographic (EEG) gamma -band bursts (around 40 Hz) when the brain is required to achieve such binding. Here we explore gamma -band EEG in autism and Williams Syndrome and demonstrate differential abnormalities in the two phenotypes. We show that despite putative processing similarities at the cognitive level, binding in Williams syndrome and autism can be dissociated at the neurophysiological level by different abnormalities in underlying brain oscillatory activity. Our study is the first to identify that binding-related gamma EEG can be disordered in humans. NeuroReport 12:2697-2700 (C) 2001 Lippincott Williams & Wilkins.

Electrophysiological correlates of category goodness

We report the results obtained from a behavioural and electrophysiological study. A synthesised continuum going from labial /ba/ to retroflex /da/ through dental /da/ was tested for category goodness. Native English speakers rated different tokens from each category as good, bad or ambiguous. The results showed that not all of the representatives of each category were ideal and that the categories tested have an internal structure. The electrophysiological study evaluated whether event related potentials (ERPs) mirrored the goodness judgements. During a passive oddball task, the same participants were exposed to native /ba/-/da/, Hindi dental /da/-retroflex /da/ and within-category /ba/-/ba/ contrasts. Results showed that participants pre-attentively perceive the differences in all cases, as shown by mis-match negativities (MMN), late positive deflections (LPD) or greater N1 and/or P2 components for deviant stimuli. Acoustic sensitivities, categorical perception and category goodness all contributed to the waveforms obtained. We attribute the ERP effects to a combination of (1) prototypes built from initial sensitivities, (2) reinforcement with exposure to one's native language and (3) no permanent loss of the initial boundaries explains the effects observed. (C) 2000 Elsevier Science B.V. All rights reserved.

Neural correlates of saccade planning in infants: A high-density ERP study

Neural correlates of saccade planning in B-month-old infants were investigated by high-density event-related potentials. Subjects made saccades to a target stimulus following a time gap from fixation stimulus offset (gap trials) or with the fixation stimulus still present (overlap trials). Like adults, infants were slower to make a saccade to the target when the fixation stimulus was still present. Strikingly, infants did not show clear evidence of the pre-saccadic components observed in adults which are thought to reflect cortical saccade planning processes. They did, however, show a left frontal positivity, which we suggest reflects cortical disinhibition of the colliculus initiated by fixation stimulus offset, and clear post-saccadic lambda waves. These results indicate that the frontal cortex already plays a role in action control by 6 months of age, while other aspects of cortical action planning may not yet be present in certain task situations.

Attention and oculomotor control: A high-density ERP study of the gap effect

In a gap paradigm, healthy adult subjects performed visually triggered saccades to peripheral targets either with the fixation stimulus remaining on (overlap trials) or going off before target onset (gap trials). All subjects showed faster reaction times in the gap trials (the gap effect). High density scalp event-related potentials were recorded time-locked to both the target stimuli and the eve movement onset. We observed three neural correlates of the gap effect: (i) a prefrontal positivity that precedes the target presentation which may reflect specific preparatory processes, (ii) an enhancement of the early cortical visual responses (P1) to the peripheral target in the gap trials, and (iii) a prolongation of parietal activity in the overlap trials relative to the gap trials prior to the saccade execution. These results suggest that several factors contribute to the gap effect, each having its own neural basis. (C) 1997 Elsevier Science Ltd.

Teleological reasoning in infancy: The infant's naive theory of rational action. A reply to Premack and Premack

We argue that Premack and Premack's criticism of our demonstration (Gergely et al., 1995) of interpreting goal-directed action in one year-olds in terms of the principle of rationality are ill-founded, and their suggested alternative test for goal-attribution is open to lower level interpretations. We show that the alterative model they propose for our data in terms of 'appropriate' change of means action is but a somewhat imprecise restatement of our account of the infant's naive theory of rational action. Finally, we elaborate and clarify our model of the teleological stance in infancy which we suggest is an as yet nonmentalistic precursor of the young child's later emerging causal theory of mind.

Review

This article reviews the book: Words, thoughts, and theories by A. Gopnik and A. Meltzoff

Aging, stimulus identification and the effect of probability: An event-related potential study

Event-related potentials (ERPs) of younger and older subjects were compared in a simple reaction time (SRT) and in two GoNogo (20% and 80% target probability) tasks. At the T5 location, the NA component (the difference between the ERPs elicited by the frequent stimuli in the GoNogo tasks on the one hand, and the ERPs in the SRT task on the other hand) emerged earlier in the younger group. The N2b was larger in the younger group, and in this group the rare stimuli of the 80% GoNogo task elicited an enlarged N2. When compared to the older group, the stimulus probability in the younger group had a larger effect on the amplitude of the late positivity. The results show age-related changes at an early stage of the information processing activity, and larger sensitivity of the orienting system in the younger subjects.

Event-related potentials and aging – identification of deviant visual-stimuli

The effects of aging on event-related potentials (ERPs) were investigated in visual tasks. The stimuli (two angles within a frame) were frequent (standard) or deviant (differing from the standard either in the orientation of the two angles, in the thickness of the frame, or in both). The target stimuli were defined either by the presence of only one deviant feature, or by the conjunction of the deviant features. The deviant stimuli elicited an increased P2, a posterior N2, on N2b, and a tate positivity (Go and Nogo P3). The latencies of all but the P2 were longer in the older subjects. In the younger group, the target stimuli elicited a larger late positivity than the non-target stimuli that had deviant features, whereas in the older group the target stimuli did not elicit a larger P3 than the stimuli with two deviant features, even when this deviant was a non-target. In contrast to the younger group, in the older group we obtained no P3 over the temporal and occipital locations. We found a reduction of P3 over the posterior location even in a group of middle-aged (mean age = 39 years) subjects. In tasks with only one target feature, the false alarm rate was higher in the elderly subjects. These results suggest a gradual age-related slowing down of the attentive processing of deviant visual patterns, and a decrease of inhibitory functions in the elderly group.

Event-related potentials and the identification of deviant visual-stimuli

The effects of deviant visual stimuli on event-related potentials were investigated in a counting task (Experiment 1) and in a reaction time task (Experiment 2). In Experiment 2 the interstimulus interval was either short or long (340 vs. 1020 ms). The stimuli (two angles within a frame) were frequent (Standard) or deviant (differing from the Standard either in the orientation of the two angles, or in the thickness of the frame, or in both of these features). In various conditions the target stimuli were defined by one of the deviant features or by the conjunction of these features. Subjects were more accurate in the counting task, and the reaction time was shortest when the target feature was the deviant angle orientation. Performance was lowest for the conjunction of the deviant features. The deviant angle orientation elicited a posterior negative wave in the 140-180 ms range. As the interstimulus interval increased, the magnitude of this component decreased. All stimuli with relevant (attended) deviant features elicited another posterior negative wave in the 180-260 ms range as well as an anterior positivity with similar latency. When the interstimulus interval was short, and the only target was the Conjunction Deviant, the summed occipital activity to the relevant features of deviant nontarget stimuli was larger than the negativity to the Conjunction Deviant. Target stimuli elicited late positive waves, which were sometimes preceded by central negativity.

Age and inter-stimulus interval effects on event-related potentials to frequent and infrequent auditory stimuli

The aim of this study was to investigate aging effects on non-attended changes of auditory stimulation, by using psychophysiological methods. Event-related potentials (ERPs) were recorded to frequent (standard; 950 Hz, p = 0.9) and infrequent (deviant; 1045 Hz, p = 0. 1) auditory stimuli in older (mean age = 60.8 years) and younger (mean age = 21.3 years) subjects. In various blocks the inter-stimulus interval (ISI) was either 800, 2400 or 7200 ms. During the experimental sessions the subjects read books, and ignored the auditory stimuli. As a function of ISI, the amplitude of the NI and the amplitude and latency of the P2 increased. The P2 amplitude was larger in the younger group. In the 120-180 ms latency range the deviant stimuli elicited more negative ERPs (mismatch negativity, MMN) than the standard stimuli. The amplitude of the MMN did not change as a function of ISI. MMN was larger in the younger group. Thus the younger subjects were more sensitive to the deviant stimuli. In the younger group, at the two shorter ISIs, the MMN was followed by a positive wave (P3a). The emergence of this component is an indication of the increased activity of the orienting system in the younger subjects, in comparison to the older age group.