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Discriminating facial cues to trustworthiness is a fundamental social skill whose developmental origins are still debated. Prior investigations used computer-generated faces, which might fail to reflect infants’ face processing expertise. Here, Event-Related Potentials (ERPs) were recorded in Caucasian adults (N = 20, 7 males, M age = 25.25 years) and 6-month-old infants (N = 21, 10 males) in response to variations in trustworthiness intensity expressed by morphed images of realistic female faces associated with explicit trustworthiness judgments (Study 1). Preferential looking behavior in response to the same faces was also investigated in infants (N = 27, 11 males) (Study 2). ERP results showed that both age groups distinguished subtle stimulus differences, and that interindividual variability in neural sensitivity to these differences were associated with infants’ temperament. No signs of stimulus differentiation emerged from infants’ looking behavior. These findings contribute to the understanding of the developmental origins of human sensitivity to social cues from faces by extending prior evidence to more ecological stimuli and by unraveling the mediating role of temperament.

The human tactile system is known to discriminate different types of touches, one of these termed & lsquo;affective touch & rsquo;, is mainly mediated by slow conducting tactile afferents (CT fibres), which are preferentially activated by slow and gentle strokes. Human infants experience self-generated tactile stimulation during prena-tal life, and they receive a large amount of affectionate touches by their caregivers from birth. This early and extended experience with tactile stimulation may likely make infants particularly sensitive to affective touch, and increasing evidence shows that this may indeed be the case. However, infants commonly experience affective touch in the context of social interactions with familiar adults (e.g., while looking at their caregiver), and recent evidence suggests that this helps them assigning affiliative and communicative meaning to the touch they are perceiving. Here we investigated the presence of visual-tactile interactions in 4 & ndash;5-month-old infants & rsquo; physiolog-ical (i.e., skin conductance) and behavioural (i.e., visual looking times) responses to visual and tactile stimulation of affective/social nature when the sources of both stimulation are not familiar to the infant. To explore whether the modulation of physiological arousal elicited by the socially-relevant bimodal stimulation is specific to infants or extends into adulthood, we also tested a group of adults. Infants (N = 25) and adults (N = 25) were stimulated on their forearm through slow stroking (i.e. affective touch) or tapping (i.e. non-affective touch) during the obser-vation of dynamic images of socially-relevant (i.e., an unfamiliar face) and non-socially-relevant (i.e., a house) stimuli. We found that the simultaneous presentation of socially-relevant visual-tactile stimuli significantly decreased infants & rsquo; & ndash; but not the adults & rsquo; & ndash; electrodermal response, suggesting that infants easily int

During the first year of life face discrimination abilities narrow toward adult human faces of the most frequently encountered ethnic group/s. Earlier studies showed that perceptual learning under laboratory-training protocols can modulate this narrowing process. Here we investigated whether natural experience acquired in everyday settings with an older sibling's face can shape the trajectory of perceptual narrowing towards adult faces. Using an infant-controlled habituation procedure we measured discrimination of adult (Experiment 1) and child faces (Experiment 2) in 3- and 9- month-old infants with and without a child sibling. Discrimination of adult faces was observed for infants at both ages, although accompanied by posthabituation preferences in opposite directions, whereas at both ages the discrimination of child faces critically depended on sibling experience. These results provide the first evidence that natural experience acquired with siblings affects the tuning properties of infant face representation.

The ability to discriminate social signals from faces is a fundamental component of human social interactions whose developmental origins are still debated. In this study, 5-year-old (N = 29) and 7-year-old children (N = 31) and adults (N = 34) made perceptual similarity and trustworthiness judgments on a set of female faces varying in level of expressed trustworthiness. All groups represented perceived similarity of the faces as a function of trustworthiness intensity, but such representation becomes more fine-grained with development. Moreover, 5-year-olds' accuracy in choosing the more trustworthy face in a pair varied as a function of children's score at the Test of Emotion Comprehension, suggesting that the ability to perform face-to-trait inferences is related to the development of emotional understanding.

The ability to learn and generalize abstract rules from sensory input – i.e., Rule Learning (RL) – is seen as pivotal to language development, and specifically to the acquisition of the grammatical structure of language. Although many studies have shown that RL in infancy is operating across different perceptual domains, including vision, no studies have directly investigated the link between infants’ visual RL and later language acquisition. Here, we conducted a longitudinal study to investigate whether 7-montholds’ ability to detect visual structural regularities predicts linguistic outcome at 2 years of age. At 7 months, infants were tested for their ability to extract and generalize ABB and ABA structures from sequences of visual shapes, and at 24 months their lexical and grammatical skills were assessed using the MacArthur-Bates CDI. Regression analyses showed that infants’ visual RL abilities selectively predicted early grammatical abilities, but not lexical abilities. These results may provide the first evidence that RL mechanisms are involved in language acquisition, and suggest that RL abilities may act as an early neurocognitive marker for language impairments.

The ability to discriminate the ordinal information embedded in magnitude-based sequences has been shown in 4-month-old infants, both for numerical and size-based sequences. At this early age, however, this ability is confined to increasing sequences, with infants failing to extract and represent decreasing order. Here we investigate whether the ability to represent order extends to duration-based sequences in 4-month-old infants, and whether it also shows the asymmetry signature previously observed for number and size. Infants were tested in an order discrimination task in which they were habituated to either increasing or decreasing variations in temporal duration, and were then tested with novel sequences composed of new temporal items whose durations varied following the familiar and the novel orders in alternation. Across three experiments, we manipulated the duration of the single temporal items and therefore of the whole sequences, which resulted in imposing more or less constraints on infants’ working memory, or general processing capacities. Results showed that infants failed at discriminating the ordinal direction in temporal sequences when the sequences had an overall long duration (Experiment 1), but succeeded when the duration of the sequences was shortened (Experiments 2 and 3). Moreover, there was no sign of the asymmetry signature previously reported for number and size, as successful discrimination was present for infants habituated to both increasing and decreasing sequences. These results suggest that sensitivity to temporal order is present very early in development, and that its functional properties are not shared with other magnitude dimensions, such as size and number.

Gli esseri umani sono ipersensibili a quelle proprietà facciali che trasmettono segnali sociali. La capacità di attribuire giudizi di affidabilità basati sui segnali del volto, vale a dire quei segnali che usiamo per dedurre se una persona può essere avvicinata in modo sicuro o piuttosto evitata, è nota per essere veloce, automatica e basata su pochissime informazioni. Questa tesi di dottorato mira a indagare: (1) se la sensibilità ai tratti di affidabilità del volto sia modulata da differenze individuali nelle attitudini sociali e comportamentali; (2) la traiettoria evolutiva di questa sensibilità; (3) se la sensibilità alle sottili variazioni degli indizi facciali all'affidabilità è un fenomeno universale o è piuttosto modulata dalla cultura e / o dall'etnia del viso. Il Capitolo 1 mira a indagare se differenze nella sensibilità percettiva e nella rappresentazione mentale di volti che variano per livello di affidabilità espressa sono associate a differenze individuali relative alla motivazione sociale. I risultati hanno mostrato che le differenze individuali nella motivazione sociale possono avere un impatto sulla quantità di esperienza sociale e quindi sul livello di sensibilità nei confronti di segnali facciali all'affidabilità. Il capitolo 2 si è concentrato sulla traiettoria evolutiva di tale sensibilità. Lo studio 2 mira a studiare in che modo la sensibilità percettiva e la rappresentazione mentale di differenze minime nell'informazione facciale che sottende la percezione di affidabilità si sviluppano nel tempo, tenendo conto delle differenze individuali nello sviluppo emotivo. I risultati hanno mostrato che la sensibilità ai segnali di affidabilità del volto e la capacità di impiegare questi segnali per generare giudizi di affidabilità è presente in età prescolare, ma matura per raggiungere livelli simili a quelli degli adulti all'età di 7 anni, sviluppandosi insieme alle capacità di comprensione delle emozioni. Gli studi 3 e 4 h, Human beings are hypersensitive to those facial properties that convey social signals. The ability to attribute trustworthiness judgements based on facial cues to trustworthiness, i.e. those cues that we use to derive whether a person can be safely approached or better avoided, is known to be fast, automatic and based on very little information. This doctoral dissertation aims at investigating: (1) whether sensitivity to facial cues to trustworthiness is modulated by individual variations in social personality characteristics; (2) the developmental trajectory of this sensitivity; (3) if sensitivity to subtle variations in facial cues to trustworthiness is a universal phenomenon or is it modulated by culture and/or face ethnicity. Chapter 1 aimed at investigating whether individual differences in fine-grained perceptual sensitivity and mental representation of facial features related to trustworthiness judgements are associated with individual differences in social motivation. Results showed that individual differences in social motivation can have an impact on the amount of social experience and thus the level of developed sensitivity to facial cues to trustworthiness. Chapter 2 focused on the developmental trajectory of such sensitivity. Study 2 aimed to investigate how perceptual sensitivity to and mental representation of fine-grained differences in facial information subtending social perception of trustworthiness develops in time, taking into account individual differences in emotional development. Results showed that sensitivity to facial cues to trustworthiness and the ability to employ these cues to generate trustworthiness judgements is present in preschool years, but matures to reach adult-like levels at the age of 7, developing together with emotion understanding abilities. Study 3 and 4 used two different EEG paradigms with 6-month-old infants to question whether this sensitivity is already present in the first year of life. Combined data coming from Stu

A wealth of studies show that human adults map ordered information onto a directional spatial continuum. We asked whether mapping ordinal information into a directional space constitutes an early predisposition, already functional prior to the acquisition of symbolic knowledge and language. While it is known that preverbal infants represent numerical order along a left-to-right spatial continuum, no studies have investigated yet whether infants, like adults, organize any kind of ordinal information onto a directional space. We investigated whether 7-month-olds' ability to learn high-order rule-like patterns from visual sequences of geometric shapes was affected by the spatial orientation of the sequences (left-to-right vs. right-to-left). Results showed that infants readily learn rule-like patterns when visual sequences were presented from left to right, but not when presented from right to left. This result provides evidence that spatial orientation critically determines preverbal infants' ability to perceive and learn ordered information in visual sequences, opening to the idea that a left-to-right spatially organized mental representation of ordered dimensions might be rooted in biologically-determined constraints on human brain development.

There has been compelling evidence favouring the idea that human adults similarly represent number and time along a horizontal Mental Number Line (MNL) and Mental Time Line (MTL), respectively. Yet, analogies drawn between the MNL and MTL have been challenged by recent studies suggesting that adults' representations of number and time arise from different spatial frames of reference: whereas the MNL relies on both hand-centred and object-centred coordinates, the MTL appears to be exclusively anchored on object-centred coordinates. To directly test this possibility, here we explored the extent to which visual and proprioceptive feedback affect children’s performance in a Number Comparison task (Experiment 1) and a Time Comparison task (Experiment 2), in which participants had to associate a lateralised key to numerical and temporal words, respectively. Five- and six-year-old children performed the task with either their hands uncrossed or crossed over the body midline (i.e., manipulation of proprioceptive feedback) and with either visual control over their hands allowed or precluded under blindfolds (i.e., manipulation of visual feedback). Results showed that children were facilitated in associating smaller/larger numbers with the left/right side of the external space, but only when hands were uncrossed and visual feedback was available. On the contrary, blindfolding and crossing their hands over the midline did not affect spatial-time mapping, as 6-year-old children showed facilitation in associating words referring to the past/future with the left/right side of the external space, irrespective of visual and proprioceptive feedback. This same effect was also present in 5-year-olds despite their difficulty in performing the Time Comparison task. Together, these findings show, for the first time, that - just like adults - young children (1) map temporal events onto space in a rightward direction as they do for numbers, and (2) anchor their spatial representation of ti

Coding the direction of others’ gestures is a fundamental human ability, since it allows the observer to attend and react to sources of potential interest in the environment. Shifts of attention triggered by action observation have been reported to occur early in infancy. Yet, the neurophysiological underpinnings of such action priming and the properties of gestures that might be crucial for it remain unknown. Here, we addressed these issues by recording electroencephalographic activity (EEG) from 6-month-old infants cued with spatially non-predictive hand grasping toward or away from the position of a target object, i.e., valid and invalid trials, respectively. Half of the infants were cued with a gesture executable by a human hand (possible gesture) and the other half with a gesture impossible to be executed by a human hand. Results show that the amplitude enhancement of the posterior N290 component in response to targets in valid trials, as compared to invalid trials, was present only for infants seeing possible gestures, while it was absent for infants seeing impossible gestures. These findings suggest that infants detect the biomechanical properties of human movements when processing hand gestures, relying on this information to orient their visual attention toward the target object.

The development of the ability to recognize the whole human body shape has long been investigated in infants, while less is known about their ability to recognize the shape of single body parts, and in particular their biomechanical constraints. This study aimed to explore whether 9- and 12-month-old infants have knowledge of a hand-grasping movement (i.e., pincer grip), being able to recognize violations of the hand's anatomical constraints during the observation of that movement. Using a preferential looking paradigm, we showed that 12-month-olds discriminate between biomechanically possible and impossible pincer grips, preferring the former over the latter (Experiment 1). This capacity begins to emerge by 9 months of age, modulated by infants' own sensorimotor experience with pincer grip (Experiment 2). Our findings indicate that the ability to visually discriminate between pincer grasps differing in their biomechanical properties develops between 9 and 12 months of age, and that experience with self-produced hand movements might help infants in building a representation of the hand that encompasses knowledge of the physical constraints of this body part.

Ordinality is a fundamental aspect of numerical cognition. However, preverbal infants’ ability to represent numerical order is poorly understood. In the present study we extended the evidence provided by Macchi Cassia, Picozzi, Girelli, and de Hevia (2012), showing that 4-month-old infants detect ordinal relationships within size-based sequences, to numerical sequences. In three experiments, we showed that at 4 months of age infants fail to represent increasing and decreasing numerical order when numerosities differ by a 1:2 ratio (Experiment 1), but they succeed when numerosities differ by a 1:3 ratio (Experiments 2 and 3). Critically, infants showed the same behavioral signature (i.e., asymmetry) described by Macchi Cassia et al. for discrimination of ordinal changes in area: they succeed at detecting increasing but not decreasing order (Experiments 2 and 3). These results support the idea of a common (or at least parallel) development of ordinal representation for the two quantitative dimensions of size and number. Moreover, the finding that the asymmetry signature, previously reported for size-based sequences, extends to numerosity, points to the existence of a common constraint in ordinal magnitude processing in the first months of life. The present findings are discussed in the context of possible evolutionary and developmental sources of the ordinal asymmetry, as well as their implication for other related cognitive abilities.

Research investigating the early development of emotional processing has focused mainly on infants' perception of static facial emotional expressions, likely restricting the amount and type of information available to infants. In particular, the question of whether dynamic information in emotional facial expressions modulates infants' neural responses has been rarely investigated. The present study aimed to fill this gap by recording 7-month-olds' event-related potentials to static (Study 1) and dynamic (Study 2) happy, angry, and neutral faces. In Study 1, happy faces evoked a faster right-lateralized negative central (Nc) component compared to angry faces. In Study 2, both happy and angry faces elicited a larger right-lateralized Nc compared to neutral faces. Irrespective of stimulus dynamicity, a larger P400 to angry faces was associated with higher scores on the Negative Affect temperamental dimension. Overall, results suggest that 7-month-olds are sensitive to facial dynamics, which might play a role in shaping the neural processing of facial emotional expressions. Results also suggest that the amount of attentional resources infants allocate to angry expressions is associated to their temperamental traits. These findings represent a promising avenue for future studies exploring the neurobiological processes involved in perceiving emotional expressions using dynamic stimuli.

Early facial experience provided by the infant's social environment is known to shape face processing abilities, which narrow during the first year of life towards adult human faces of the most frequently encountered ethnic groups. Here we explored the hypothesis that natural variability in facial input may delay neural commitment to face processing by testing the impact of early natural experience with siblings on infants' brain responses. Event-Related Potentials (ERPs) evoked by upright and inverted adult and child faces were compared in two groups of 10-month-old infants with (N=21) and without (N=22) a child sibling. In first-born infants, P1 ERP component showed specificity to upright adult faces that carried over to the subsequent N290 and P400 components. In infants with siblings no inversion effects were observed. Results are discussed in the context of evidence from the language domain, showing that neural commitment to phonetic contrasts emerges later in bilinguals than in monolinguals, and that this delay facilitates subsequent learning of previously unencountered sounds of new languages

When adding or subtracting quantities, adults tend to overestimate addition outcomes and underestimate subtraction outcomes. They also shift visuospatial attention to the right when adding and to the left when subtracting. These operational momentum phenomena are thought to reflect an underlying representation in which small magnitudes are associated with the left side of space and large magnitudes with the right side of space. Currently, there is limited research on operational momentum in early childhood or for operations other than addition and subtraction. The current study tested whether English-speaking 3- and 4-year-old children and college-aged adults exhibit operational momentum when ordering quantities. Participants were presented with two experimental blocks. In one block of trials, they were tasked with choosing the same quantity they had previously seen three times; in the other block, they were asked to generate the next quantity in a doubling sequence composed of three ascending quantities. A bias to shift attention to the right after an ascending operation was found in both age groups, and a bias to overestimate the next sequential quantity during an ascending ordering operation was found in adults under conditions of uncertainty. These data suggest that, for children, the spatial biases during operating are more pronounced than the mis-estimation biases. These findings highlight the spatial underpinnings of operational momentum and suggest that both very young children and adults conceptualize quantity along a horizontal continuum during ordering operations, even before formal schooling.

One of the most important sources of social information is the human face, on whose appearance we easily form social judgments: Adults tend to attribute a certain personality to a stranger based on minimal facial cues, and after a short exposure time. Previous studies shed light on the cognitive and neural mechanisms underlying the ability to discriminate facial properties conveying social signals, but the underlying processes supporting individual differences remain poorly understood. In the current study, we explored whether differences in sensitivity to facial cues to trustworthiness and in representing such cues in a multidimensional space are associated with individual variability in social attitude, as measured by the extraversion/introversion dimension. Participants performed a task where they assessed the similarity between faces that varied in the level of trustworthiness, and multidimensional scaling analyses were performed to describe perceptual similarity in a multidimensional representational space. Extraversion scores impacted RTs, but not accuracy or face representation, making less extraverted individuals slower in detecting similarity of faces based on physical cues to trustworthiness. These findings are discussed from an ontogenetic perspective, where reduced social motivation might constrain perceptual attunement to social cues from faces, without affecting the structuring of the face representational space.