Asymmetry in the detection of shapes from shading in infants1

Abstract: We investigated 3‐ and 4‐month‐old infants’ sensitivity to differences defined by shading using a paired‐comparison familiarity/novelty preference procedure. Infants were familiarized with a pair of displays consisting of homogeneous shaded disks, and then were tested with two displays: the familiar display and a novel one containing shaded disks with reversed polarity (defined as the target). Experiment 1 examined two assumptions on discerning shapes from shading in infants by manipulating the orientations in the shading gradient of stimuli. When the orientation of the shading gradient was vertical, 4‐month‐old infants looked at the novel display for a longer time during the test trial. However, they failed to detect differences when the orientation of shading gradients was horizontal. Three‐month‐old infants did not detect differences in either orientation of the shading gradient. Experiment 2 examined asymmetry in the detection of convex versus concave shapes. Four‐month‐old infants failed to detect the target when the orientation of the shading grating was vertical and the target was convex. Taken with the results of Experiment 1, concave shapes were much easier to detect than convex shapes for 4‐month‐olds. This asymmetry suggests that 4‐month‐old infants process shading information in the same manner as adults.     

Communicative hand‐waving gestures facilitate object learning in preverbal infants

The theory of natural pedagogy has proposed that infants can use ostensive signals, including eye contact, infant‐directed speech, and contingency to learn from others. However, the role of bodily gestures, such as hand‐waving, in social learning has been largely ignored. To address this gap in the literature, this study sought to determine whether 4‐month‐old infants exhibited a preference for horizontal or vertical (control) hand‐waving gestures. We also examined whether horizontal hand‐waving gestures followed by pointing facilitated the process of object learning in 9‐month‐old infants. Results showed that 4‐month‐old infants preferred horizontal hand‐waving gestures to vertical hand‐waving gestures, even when featural and contextual information were removed. Furthermore, horizontal hand‐waving gestures induced identity encoding for cued objects, whereas vertical gestures did not. These findings highlight the role of communicative intent embedded in bodily movements and indicate that hand‐waving can serve as a new type of ostensive signal.     

Two‐ to three‐month‐old infants prefer moving face patterns to moving top‐heavy patterns

Newborn infants prefer face‐like patterns over non‐face‐like patterns. This preference is explained by newborns' preference for a “top‐heavy” configuration, that is, for geometric patterns that have more elements in the upper part than in the lower part of the configuration (Simion, Valenza, Macchi Cassia, Turati, & Umiltà, 2002). However, for 3‐month‐old infants, face preference cannot be explained only by a preference for “top‐heaviness” because they prefer veridical face images over top‐heavy images. The present study used geometric patterns to investigate whether 2‐ to 3‐month‐old infants' preference for face patterns exceeds their preference for top‐heavy configurations. In Experiment 1, we revealed that the infants preferred the face pattern to the top‐heavy pattern only when the internal elements of the patterns were presented with face‐like movements. This facilitative effect of internal movement was observed again in Experiment 2, in which the patterns were presented with non‐face‐like movements. These results suggest that 2‐ to 3‐month‐olds' preference for geometric face patterns is greater than their preference for top‐heavy patterns only when aided by the movement of internal elements.     

Sensitivity to auditory‐tactile colocation in early infancy

An ability to detect the common location of multisensory stimulation is essential for us to perceive a coherent environment, to represent the interface between the body and the external world, and to act on sensory information. Regarding the tactile environment “at hand”, we need to represent somatosensory stimuli impinging on the skin surface in the same spatial reference frame as distal stimuli, such as those transduced by vision and audition. Across two experiments we investigated whether 6‐ (n = 14; Experiment 1) and 4‐month‐old (n = 14; Experiment 2) infants were sensitive to the colocation of tactile and auditory signals delivered to the hands. We recorded infants’ visual preferences for spatially congruent and incongruent auditory‐tactile events delivered to their hands. At 6 months, infants looked longer toward incongruent stimuli, whilst at 4 months infants looked longer toward congruent stimuli. Thus, even from 4 months of age, infants are sensitive to the colocation of simultaneously presented auditory and tactile stimuli. We conclude that 4‐ and 6‐month‐old infants can represent auditory and tactile stimuli in a common spatial frame of reference. We explain the age‐wise shift in infants’ preferences from congruent to incongruent in terms of an increased preference for novel crossmodal spatial relations based on the accumulation of experience. A comparison of looking preferences across the congruent and incongruent conditions with a unisensory control condition indicates that the ability to perceive auditory‐tactile colocation is based on a crossmodal rather than a supramodal spatial code by 6 months of age at least.     

Infants' perception of human body orientation and the effect of a surrounding square

We examined two hypotheses about infants' perception of orientation. The first is that infants develop an expectation that the human body is normally vertical. To examine this hypothesis, we compared the preferential looking to vertical and oblique versions of a silhouette of a human body, to an inverted body, and to a grating. Our second hypothesis is that presenting a figure inside a frame affects the perception of orientation. To examine the second hypothesis, we placed the figure inside a surrounding square that was oriented normally or at an oblique angle. Four‐ to seven‐month‐old infants (N = 78) participated. The results showed that 6–7‐month‐old infants preferred the oblique human body presented upright; no such preference was observed for the inverted body or the grating. For all types of displays, the surrounding square influenced preferences. Our results suggest that (a) 6–7‐month‐old infants have specific expectations about the orientation of the human body, and (b) surrounding displays with a square could influence the perception of the orientation of the human body, as well as that of a grating.     

Development of ordinal sequence perception in infancy

Perception of the ordinal position of a sequence element is critical to many cognitive and motor functions. Here, the prediction that this ability is based on a domain‐general perceptual mechanism and, thus, that it emerges prior to the emergence of language was tested. Infants were habituated with sequences of moving/sounding objects and then tested for the ability to perceive the invariant ordinal position of a single element (Experiment 1) or the invariant relative ordinal position of two adjacent elements (Experiment 2). Experiment 1 tested 4‐ and 6‐month‐old infants and showed that 4‐month‐old infants focused on conflicting low‐level sequence statistics and, therefore, failed to detect the ordinal position information, but that 6‐month‐old infants ignored the statistics and detected the ordinal position information. Experiment 2 tested 6‐, 8‐, and 10‐month‐old infants and showed that only 10‐month‐old infants detected relative ordinal position information and that they could only accomplish this with the aid of concurrent statistical cues. Together, these results indicate that a domain‐general ability to detect ordinal position information emerges during infancy and that its initial emergence is preceded and facilitated by the earlier emergence of the ability to detect statistical cues.     

Development of chromatic induction in infancy

The perception of colour in an embedded field is affected by the surround colour. This phenomenon is known as chromatic induction. In the present study we investigated whether the colour perception by infants aged 5–7 months could be affected by the surround colour. In Experiments 1 and 2 each stimulus was composed of an array of six squares in tandem. The colour appearance of the array in the familiarization stimulus was established by chromatic induction. In Experiment 1 we used familiarization stimuli that were perceived as two‐colour array with a two‐colour surround. In Experiment 2 we used a familiarization stimulus that was perceived as a uniform‐colour array with a two‐colour surround. In the test phase, the uniform‐colour array and the two‐colour array were presented on a white uniform‐colour surround in both experiments. The results showed that in Experiment 1 the 5‐ and 7‐month‐old infants had novelty preference for the uniform‐colour test array. This suggested that the infants' colour perception could be affected by surround colour. The results of Experiment 2 showed that the 7‐month‐olds showed a novelty preference for the two‐colour test array, but the 5‐month‐olds showed no novelty preference. This suggested that 7‐month‐olds' colour perception could be affected by surround colour, but that of 5‐month‐olds could not. We discuss the contradiction of the results between Experiments 1 and 2. Copyright © 2007 John Wiley & Sons, Ltd.     

The movement of internal facial features elicits 7 to 8‐month‐old infants' preference for face patterns

A preference for static face patterns is observed in newborns and disappears around 3 months after birth. A previous study has demonstrated that 5‐month‐old infants prefer schematic faces only when the internal features are moving, suggesting that face‐specific movement enhances infants' preference. The present study investigates the facilitative effect of the movement of internal facial features on infants' preference. To examine infants' preference, we used animated face patterns consisting of a head‐shaped contour and three disk blobs. The inner blobs expanded and contracted to represent the opening and closing of the eyes and mouth, and were constrained to open and close only in a biologically possible vertical direction resembling the facial muscle structure. We compared infants' preferential looking time for this vertically moving (VM) face pattern with their looking time for a horizontally moving (HM) face pattern in which blobs transformed at the same speed in a biologically impossible, horizontal direction. In Experiment 1, 7 to 8‐month‐olds preferred the VM to the HM, but 5 to 6‐month‐olds did not. However, the preference was diminished in both cases when the moving face patterns were presented without contour (Experiment 2). Our results suggest that internal facial features with vertical movements promote face preference in 7 to 8‐month‐olds. Copyright © 2011 John Wiley & Sons, Ltd.     

Perception of motion transparency in 5-month-old infants

We investigated the perceptual development of motion transparency in 3- to 5-month-old infants. In two experiments we tested a total of 55 infants and examined their preferential looking behaviour. In experiment 1, we presented transparent motion as a target, and uniform motion as a non-target consisting of random-dot motions. We measured the time during which infants looked at the target and non-target stimuli. In experiment 2, we used paired-dot motions (Qian et al, 1994 Journal of Neuroscience 14 7357-7366) as non-targets and also measured target looking time. We calculated the ratio of the target looking time to the total target and no-target looking time. In both experiments we controlled the dot size, speed, the horizontal travel distance of the dots, and the motion pattern of the dots. The results demonstrated that 5-month-old infants showed a statistically significant preference for motion transparency in almost all stimulus conditions, whereas the preference in 3- and 4-month-old infants depended on stimulus conditions. These results suggest that the sensitivity to motion transparency was robust in 5-month-olds, but not in 3- and 4-month-olds.     

Visual cues of motion that trigger animacy perception at birth: the case of self‐propulsion

Self‐propelled motion is a powerful cue that conveys information that an object is animate. In this case, animate refers to an entity's capacity to initiate motion without an applied external force. Sensitivity to this motion cue is present in infants that are a few months old, but whether this sensitivity is experience‐dependent or is already present at birth is unknown. Here, we tested newborns to examine whether predispositions to process self‐produced motion cues underlying animacy perception were present soon after birth. We systematically manipulated the onset of motion by self‐propulsion (Experiment 1) and the change in trajectory direction in the presence or absence of direct contact with an external object (Experiments 2 and 3) to investigate how these motion cues determine preference in newborns. Overall, data demonstrated that, at least at birth, the self‐propelled onset of motion is a crucial visual cue that allowed newborns to differentiate between self‐ and non‐self‐propelled objects (Experiment 1) because when this cue was removed, newborns did not manifest any visual preference (Experiment 2), even if they were able to discriminate between the stimuli (Experiment 3). To our knowledge, this is the first study aimed at identifying sensitivity in human newborns to the most basic and rudimentary motion cues that reliably trigger perceptions of animacy in adults. Our findings are compatible with the hypothesis of the existence of inborn predispositions to visual cues of motion that trigger animacy perception in adults.     

Who's my little monkey? Effects of infant‐directed speech on visual retention in infant rhesus macaques

Both human and nonhuman primate adults use infant‐directed facial and vocal expressions across many contexts when interacting with infants (e.g., feeding, playing). This infant‐oriented style of communication, known as infant‐directed speech (IDS), seems to benefit human infants in numerous ways, including facilitating language acquisition. Given the variety of contexts in which adults use IDS, we hypothesized that IDS supports learning beyond the linguistic domain and that these benefits may extend to nonhuman primates. We exposed 2.5‐month‐old rhesus macaque infants (N = 15) to IDS, adult‐directed speech (ADS), and a non‐social control (CTR) during a video presentation of unrelated stimuli. After a 5‐ or 60‐minute delay, infants were shown the familiar video side‐by‐side with a novel video. Infants exhibited a novelty preference after the 5‐minute delay, but not after the 60‐minute delay, in the ADS and CTR conditions, and a novelty preference in the IDS condition only after the 60‐minute delay. These results are the first to suggest that exposure to IDS affects infants’ long‐term memory, even in non‐linguistic animals.     

Binocular vision in infancy: Responsiveness to uncrossed horizontal disparity

This research explored the onset of stereopsis, the ability to perceive depth from the different views provided by the two eyes. In a longitudinal study, infants were tested weekly from 6 to 20 weeks of age. The primary goal of the study was to establish the onset and the early development of sensitivity to uncrossed horizontal disparity. The infant participants were shown dynamic random dot stereograms displaying two squares, one with uncrossed horizontal disparity (0.5°) and one with vertical disparity (0.5°). The stimuli were presented on an autostereoscopic monitor. We used two methods, the forced-choice preferential looking (FPL) method and the classical natural preference (CNP) method, to measure whether the infants preferred the uncrossed over the vertical disparity display. According to the FPL data, the mean relative preferences for horizontal over vertical disparity were significantly greater than chance probability (0.50) from 13 weeks of age onward. With the CNP method we found significant preferences for uncrossed horizontal disparity from 15 weeks onward. The FPL method was hence more sensitive than the CNP method as it indicated an earlier onset of responsiveness to stereoscopic information.     

Learning unfamiliar faces in infants: The advantage of the regular sequence presentation and the three‐quarter view superiority

We investigated the effect of the regular sequence of different views and the three‐quarter view effect on the learning of unfamiliar faces by infants. 3–8‐month‐old infants were familiarized with unfamiliar female faces in either the regular condition (presenting 11 different face views from the frontal view to the left‐side profile view in regular order) or the random condition (presenting the same 11 different face views in random order). Following the familiarization, infants were tested with a pair of a familiarized and a novel female face either in a three‐quarter (Experiment 1) or in a profile view (Experiment 2). Results showed that only 6–8‐month‐old infants could identify a familiarized face in the regular condition when they were tested in three‐quarter views. In contrast, 6–8‐month‐old infants showed no significant novelty preference in profile views. The results suggest that the regular sequence of different face views promotes the learning of unfamiliar faces by infants over 6 months old. Moreover, our findings imply that the three‐quarter view effect appears in infants.     

Overcoming the other‐race effect in infancy with multisensory redundancy: 10–12‐month‐olds discriminate dynamic other‐race faces producing speech

We tested 4–6‐ and 10–12‐month‐old infants to investigate whether the often‐reported decline in infant sensitivity to other‐race faces may reflect responsiveness to static or dynamic/silent faces rather than a general process of perceptual narrowing. Across three experiments, we tested discrimination of either dynamic own‐race or other‐race faces which were either accompanied by a speech syllable, no sound, or a non‐speech sound. Results indicated that 4–6‐ and 10–12‐month‐old infants discriminated own‐race as well as other‐race faces accompanied by a speech syllable, that only the 10–12‐month‐olds discriminated silent own‐race faces, and that 4–6‐month‐old infants discriminated own‐race and other‐race faces accompanied by a non‐speech sound but that 10–12‐month‐old infants only discriminated own‐race faces accompanied by a non‐speech sound. Overall, the results suggest that the ORE reported to date reflects infant responsiveness to static or dynamic/silent faces rather than a general process of perceptual narrowing.     

Joint attention and object learning in 5‐ and 7‐month‐old infants

We examined the effects of joint attention for object learning in 5‐ and 7‐month‐old infants. Infants interacted with an adult social partner who taught them about a novel toy in two conditions. In the Joint Attention condition, the adult spoke about the toy while alternating gaze between the infant and the toy, while in the Object Only condition, the adult looked to the toy and to a spot on the ceiling, but never at the infant. In the test trials following each social interaction, we presented infants with the ‘familiarization’ toy and a novel toy, and monitored looking times to each object. We found that 7‐month‐olds looked significantly longer to the novel toy following the Joint Attention relative to the Object Only condition, while 5‐month‐old infants did not show a significant difference across conditions. We interpret these results to suggest that joint attention facilitated 7‐month‐old infants' encoding of information about the familiarization object. Implications for the ontogeny of infant learning in joint attention contexts are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Development of category formation for faces differing by age in 9‐ to 12‐month‐olds: An effect of experience with infant faces

We examined category formation for faces differing in age in 9‐ and 12‐month‐olds, and the influence of exposure to infant faces on such ability. Infants were familiarized with adult or infant faces, and then tested with a novel exemplar from the familiarized category paired with a novel exemplar from a novel category (Experiment 1). Both age groups formed discrete categories of adult and infant faces, but exposure to infant faces in everyday life did not modulate performance. The same task was conducted with child versus infant faces (Experiment 2). Whereas 9‐month‐olds preferred infant faces after familiarization with child faces, but not child faces after familiarization with infant faces, 12‐month‐olds formed discrete categories of child and infant faces. Moreover, more exposure to infant faces correlated with higher novel category preference scores when infants were familiarized with infant faces in 12‐month‐olds, but not 9‐month‐olds. The 9‐month‐old asymmetry did not reflect spontaneous preference for infant over child faces (Experiment 3). These findings indicate that 9‐ and 12‐month‐olds can form age‐based categories of faces. The ability of 12‐month‐olds to form separate child and infant categories suggests that they have a more exclusive representation of face age, one that may be influenced by prior experience with infant faces.     

The neural correlates of orienting to walking direction in 6‐month‐old infants: An ERP study

The ability to detect social signals represents a first step to enter our social world. Behavioral evidence has demonstrated that 6‐month‐old infants are able to orient their attention toward the position indicated by walking direction, showing faster orienting responses toward stimuli cued by the direction of motion than toward uncued stimuli. The present study investigated the neural mechanisms underpinning this attentional priming effect by using a spatial cueing paradigm and recording EEG (Geodesic System 128 channels) from 6‐month‐old infants. Infants were presented with a central point‐light walker followed by a single peripheral target. The target appeared randomly at a position either congruent or incongruent with the walking direction of the cue. We examined infants' target‐locked event‐related potential (ERP) responses and we used cortical source analysis to explore which brain regions gave rise to the ERP responses. The P1 component and saccade latencies toward the peripheral target were modulated by the congruency between the walking direction of the cue and the position of the target. Infants' saccade latencies were faster in response to targets appearing at congruent spatial locations. The P1 component was larger in response to congruent than to incongruent targets and a similar congruency effect was found with cortical source analysis in the parahippocampal gyrus and the anterior fusiform gyrus. Overall, these findings suggest that a type of biological motion like the one of a vertebrate walking on the legs can trigger covert orienting of attention in 6‐month‐old infants, enabling enhancement of neural activity related to visual processing of potentially relevant information as well as a facilitation of oculomotor responses to stimuli appearing at the attended location.     

Bimodal emotion congruency is critical to preverbal infants’ abstract rule learning

Extracting general rules from specific examples is important, as we must face the same challenge displayed in various formats. Previous studies have found that bimodal presentation of grammar‐like rules (e.g. ABA) enhanced 5‐month‐olds’ capacity to acquire a rule that infants failed to learn when the rule was presented with visual presentation of the shapes alone (circle‐triangle‐circle) or auditory presentation of the syllables (la‐ba‐la) alone. However, the mechanisms and constraints for this bimodal learning facilitation are still unknown. In this study, we used audio‐visual relation congruency between bimodal stimulation to disentangle possible facilitation sources. We exposed 8‐ to 10‐month‐old infants to an AAB sequence consisting of visual faces with affective expressions and/or auditory voices conveying emotions. Our results showed that infants were able to distinguish the learned AAB rule from other novel rules under bimodal stimulation when the affects in audio and visual stimuli were congruently paired (Experiments 1A and 2A). Infants failed to acquire the same rule when audio‐visual stimuli were incongruently matched (Experiment 2B) and when only the visual (Experiment 1B) or the audio (Experiment 1C) stimuli were presented. Our results highlight that bimodal facilitation in infant rule learning is not only dependent on better statistical probability and redundant sensory information, but also the relational congruency of audio‐visual information. A video abstract of this article can be viewed at https://m.youtube.com/watch?v=KYTyjH1k9RQ     

Infant preference for female faces occurs for same‐ but not other‐race faces

There has been a recent surge of interest in the question of how infants respond to the social attributes of race and gender information in faces. This work has demonstrated that by 3 months of age, infants will respond preferentially to same‐race faces and faces depicting the gender of the primary caregiver. In the current study, we investigated emergence of the female face preference for same‐ versus other‐race faces to examine whether the determinants of preference for face gender and race are independent or interactive in young infants. In Expt 1, 3‐month‐old Caucasian infants displayed a preference for female over male faces when the faces were Caucasian, but not when the faces were Asian. In Expt 2, new‐born Caucasian infants did not demonstrate a preference for female over male faces for Caucasian faces. The results are discussed in terms of a face prototype that becomes progressively tuned as it is structured by the interaction of the gender and race of faces that are experienced during early development.     

Asymmetrical cortical processing of radial expansion / contraction in infants and adults

We report asymmetrical cortical responses (steady‐state visual evoked potentials) to radial expansion and contraction in human infants and adults. Forty‐four infants (22 3‐month‐olds and 22 4‐month‐olds) and nine adults viewed dynamic dot patterns which cyclically (2.1 Hz) alternate between radial expansion (or contraction) and random directional motion. The first harmonic (F1) response in the steady‐state VEP response must arise from mechanisms sensitive to the global radial motion structure. We compared F1 amplitudes between expansion‐random and contraction‐random motion alternations. F1 amplitudes for contraction were significantly larger than those for expansion for the older infants and adults but not for the younger infants. These results suggest that the human cortical motion mechanisms have asymmetrical sensitivity for radial expansion vs. contraction, which develops at around 4 months of age. The relation between development of sensitivity to radial motion and cortical motion mechanisms is discussed.