Online processing of native and non-native phonemic contrasts in early bilinguals.

There is considerable debate about whether bilinguals can distinguish L2 phonemic contrasts as efficiently as first language speakers can. To test this issue, a group of highly proficient Spanish-dominant Catalan-Spanish bilinguals (who had been exposed to Catalan between the ages of 3 and 4, but who, previous to this age, had been exposed only to Spanish) and another group of Catalan-dominant bilinguals (who had been exposed to Catalan from birth) were compared in a gating task. We developed a variation of the gating procedure that included a two-alternative forced choice test after each fragment was played. The differences between the two alternatives consisted of phonemic contrasts existing in Catalan but not in Spanish. Four contrasts were tested: two vocalic contrasts [symbols: see text] and two consonantal contrasts [symbols: see text]. The results showed that Spanish-dominant bilinguals, even the subset who were able to make correct identifications at the last gate, systematically performed worse than the group of Catalan-dominant bilinguals, needing longer portions of the signal to be able to correctly identify the stimuli. We argue that these results support the hypothesis that L1 shapes the perceptual system at early stages of development in such a way that it will determine the perception of non-native phonemic contrasts, even if there is extensive and early exposure to L2.     

Sensitivity of 5- and 7-month-old infants to pictorial depth information

An Ames (1951, Psychological Monographs, 65(1, Whole No. 324)) static trapezoidal window, under monocular view, was used to test young infants' responsiveness to pictorial depth. When adults view this display monocularly with the smaller side of the window rotated toward them, they report that the orientation of the display becomes ambiguous: When the head is moved, the window may appear to be in the fronto-parallel plane or either side may appear closer. The 7-month-olds we tested appeared to experience a similar ambiguity; they reached to the near side of the rotated trapezoidal window with significantly less consistency or directedness than infants in a control group tested with a rotated object that lacked pictorial depth information. When 5-month-olds were tested, however, they reached with equal consistency to the closer side of the trapezoidal window and of the control display, apparently uninfluenced by the pictorial depth information available in the trapezoidal window. Thus, sensitivity to the pictorial information for depth that is present in the trapezoidal window appears to develop after the age of 22 weeks.     

Visual speech contributes to phonetic learning in 6-month-old infants

Previous research has shown that infants match vowel sounds to facial displays of vowel articulation [Kuhl, P. K., & Meltzoff, A. N. (1982). The bimodal perception of speech in infancy. Science, 218, 1138–1141; Patterson, M. L., & Werker, J. F. (1999). Matching phonetic information in lips and voice is robust in 4.5-month-old infants. Infant Behaviour & Development, 22, 237–247], and integrate seen and heard speech sounds [Rosenblum, L. D., Schmuckler, M. A., & Johnson, J. A. (1997). The McGurk effect in infants. Perception & Psychophysics, 59, 347–357; Burnham, D., & Dodd, B. (2004). Auditory-visual speech integration by prelinguistic infants: Perception of an emergent consonant in the McGurk effect. Developmental Psychobiology, 45, 204–220]. However, the role of visual speech in language development remains unknown. Our aim was to determine whether seen articulations enhance phoneme discrimination, thereby playing a role in phonetic category learning. We exposed 6-month-old infants to speech sounds from a restricted range of a continuum between /ba/ and /da/, following a unimodal frequency distribution. Synchronously with these speech sounds, one group of infants (the two-category group) saw a visual articulation of a canonical /ba/ or /da/, with the two alternative visual articulations, /ba/ and /da/, being presented according to whether the auditory token was on the /ba/ or /da/ side of the midpoint of the continuum. Infants in a second (one-category) group were presented with the same unimodal distribution of speech sounds, but every token for any particular infant was always paired with the same syllable, either a visual /ba/ or a visual /da/. A stimulus-alternation preference procedure following the exposure revealed that infants in the former, and not in the latter, group discriminated the /ba/–/da/ contrast. These results not only show that visual information about speech articulation enhances phoneme discrimination, but also that it may contribute to the learning of phoneme boundaries in infancy.     

Statistical inference and sensitivity to sampling in 11-month-old infants

Research on initial conceptual knowledge and research on early statistical learning mechanisms have been, for the most part, two separate enterprises. We report a study with 11-month-old infants investigating whether they are sensitive to sampling conditions and whether they can integrate intentional information in a statistical inference task. Previous studies found that infants were able to make inferences from samples to populations, and vice versa [Xu, F., & Garcia, V. (2008). Intuitive statistics by 8-month-old infants. Proceedings of the National Academy of Sciences of the United States of America, 105, 5012-5015]. We found that when employing this statistical inference mechanism, infants are sensitive to whether a sample was randomly drawn from a population or not, and they take into account intentional information (e.g., explicitly expressed preference, visual access) when computing the relationship between samples and populations. Our results suggest that domain-specific knowledge is integrated with statistical inference mechanisms early in development.     

Didactic adjustments in fathers' and mothers' speech to their 3-month-old infants

Vocal dialogues of 3-month-old infants with their mothers and fathers were recorded during dyadic interactions in the laboratory. Six-minute speech samples were analyzed for syntacticlexical and temporal-melodic features. Both parents adopted strikingly similar speech registers. Segmentation, reduction in syntactic complexity, repetitiveness, and slow tempo were more marked than reported for parental speech to children above 1 year. However, rather than providing proper linguistic models, parents utilized simplified patterns of expressive melodic contours as the most salient units of speech. This tendency is interpretable as age-specific adjustment to infants' integrative capacities. Structural similarities between maternal and paternal baby talk by far outweighed a few quantitative differences. The intuitive nature of recourse to basic nonverbal properties of vocal communication, together with universality across sex, favors the assumption that baby talk is a part of species-specific didactic support to infant communicative development.     

Emotional facial expressions affect visual rule learning in 7- to 8-month-old infants

Rule learning (RL) is an implicit learning mechanism that allows infants to detect and generalize rule-like repetition-based patterns (such as ABB and ABA) from a sequence of elements. Increasing evidence shows that RL operates both in the auditory and the visual domain and is modulated by the perceptual expertise with the to-be-learned stimuli. Yet, whether infants’ ability to detect a high-order rule from a sequence of stimuli is affected by affective information remains a largely unexplored issue. Using a visual habituation paradigm, we investigated whether the presence of emotional expressions with a positive and a negative value (i.e., happiness and anger) modulates 7- to 8-month-old infants’ ability to learn a rule-like pattern from a sequence of faces of different identities. Results demonstrate that emotional facial expressions (either positive and negative) modulate infants’ visual RL mechanism, even though positive and negative facial expressions affect infants’ RL in a different manner: while anger disrupts infants’ ability to learn the rule-like pattern from a face sequence, in the presence of a happy face infants show a familiarity preference, thus maintaining their learning ability. These findings show that emotional expressions exert an influence on infants’ RL abilities, contributing to the investigation on how emotion and cognition interact in face processing during infancy.     

Timing strategies used in defensive blinking to optical collisions in 5- to 7-month-old infants

When objects approach on a collision course, young babies will blink to protect their eyes. The timing of the blink is crucial, since it serves to protect the eyes from being injured. The image of a looming virtual object approached infants under different constant velocities and constant accelerations. The youngest infants (5–6 months) blinked when the image of the virtual object reached a threshold visual angle, while older infants (6–7 months) geared their blinks to the image’s time-to-collision. Infants using a strategy based on time coped successfully with all approach conditions, while infants using a strategy based on visual angle had difficulty with the fastest accelerative approach condition. The findings indicate that infants around 6 months of age shift to a more sophisticated strategy based on time, allowing them to deal with more demanding perceptual tasks.     

Perceptual transparency in 3- to 4-month-old infants

We examined perceptual transparency in infants. In a previous study, Johnson and Aslin (2000 Developmental Psychology 36 808 - 816) found that 4-month-olds could perceive transparency in a moving chromatic display, but not in an achromatic display. In this study, we further examined perceptual transparency in infants using a static achromatic display. Considering the development of figural organisation and contrast sensitivity, we assumed that 3- to 4-month-olds would perceive transparency even in a static achromatic display. We created a transparency and a non-transparent display composed of a partially overlapping circle and square, by switching the colours. Infants aged 3 to 4 months (n = 24) were familiarised with the transparency display (experiment 1) or with the non-transparent display (experiment 2). Then, they were confronted with a uniform colour and a two-colour figure. Infants showed novelty preference for the two-colour figure after they had been familiarised with the transparency display (experiment 1), but not after they had been familiarised with the non-transparent display (experiment 2). These results suggest that 3- to 4-month-old infants can perceive transparency in a static achromatic display.     

Structural generalizations over consonants and vowels in 11-month-old infants

Recent research has suggested consonants and vowels serve different roles during language processing. While statistical computations are preferentially made over consonants but not over vowels, simple structural generalizations are easily made over vowels but not over consonants. Nevertheless, the origins of this asymmetry are unknown. Here we tested if a lifelong experience with language is necessary for vowels to become the preferred target for structural generalizations. We presented 11-month-old infants with a series of CVCVCV nonsense words in which all vowels were arranged according to an AAB rule (first and second vowels were the same, while the third vowel was different). During the test, we presented infants with new words whose vowels either followed or not, the aforementioned rule. We found that infants readily generalized this rule when implemented over the vowels. However, when the same rule was implemented over the consonants, infants could not generalize it to new instances. These results parallel those found with adult participants and demonstrate that several years of experience learning a language are not necessary for functional asymmetries between consonants and vowels to appear.     

A comparison of monocular and binocular depth perception in 5- and 7-month-old infants

Monocular depth perception was compared with binocular depth perception in 5- and 7-month-old infants. Reaching was used as the dependent measure. Two objects, identical except in size, were presented simultaneously to each infant. The smaller object was within reach for the infants while the larger object was just beyond reach. The two objects subtended equal visual angles from the infants' observation point. With binocular presentation, 96% of the 7-month-olds' reaches and 89% of the 5-month-olds' reaches were for the nearer object. With monocular presentation, 58% of the 7-month-olds' reaches and 65% of the 5-month-olds' reaches were for the nearer object. The reaching preferences observed in the monocular condition indicated sensitivity to monocular depth information (motion parallax, accommodation, and relative size information were available). Binocular viewing, however, resulted in a far more consistent tendency to reach for the nearer object. This result suggests that the infants' perception of the objects' distances was more veridical in the binocular condition than in the monocular condition.     

Syllabic pitch perception in 2- to 3-month-old infants

The pitch patterns present in speech addressed to infants may play an important role in perceptual processing by infants. In this study, the high-amplitude sucking procedure was used to assess discrimination by 2- to 3-month-old infants of rising versus falling pitch patterns in 400-msec synthetic [ra] and [la] tokens. The syllables’ intonation contour was modeled on infant-directed speech, and covered a range characteristic of an adult female speaker (180–300 Hz). Group data indicated that the 2- to 3-month-old infants discriminated the pitch contour for both stimuli. Results are discussed with reference to previous studies of syllabic pitch perception.     

Integrating physical constraints in statistical inference by 11-month-old infants

Much research on cognitive development focuses either on early-emerging domain-specific knowledge or domain-general learning mechanisms. However, little research examines how these sources of knowledge interact. Previous research suggests that young infants can make inferences from samples to populations (Xu & Garcia, 2008) and 11- to 12.5-month-old infants can integrate psychological and physical knowledge in probabilistic reasoning (Teglas, Girotto, Gonzalez, & Bonatti, 2007; Xu & Denison, 2009). Here, we ask whether infants can integrate a physical constraint of immobility into a statistical inference mechanism. Results from three experiments suggest that, first, infants were able to use domain-specific knowledge to override statistical information, reasoning that sometimes a physical constraint is more informative than probabilistic information. Second, we provide the first evidence that infants are capable of applying domain-specific knowledge in probabilistic reasoning by using a physical constraint to exclude one set of objects while computing probabilities over the remaining sets.     

Brain activity differentiates face and object processing in 6-month-old infants.

Event-related potentials were used to determine whether infants, like adults, show differences in spatial and temporal characteristics of brain activation during face and object recognition. Three aspects of visual processing were identified: (a) differentiation of face vs. object (P400 at occipital electrode was shorter latency for faces), (b) recognition of familiar identity (Nc, or negative component, at fronto-temporal electrodes [FTEs] was of larger amplitude for familiar stimuli), and (c) encoding novelty (slow wave at FTEs was larger for unfamiliar stimuli). The topography of the Nc was influenced by category type: Effects of familiarity were limited to the midline and right anterior temporal electrodes for faces but extended to all temporal electrodes for objects. Results show that infants' experience with specific examples within categories and their general category knowledge influence the neural correlates of visual processing.     

When cues collide: use of stress and statistical cues to word boundaries by 7- to 9-month-old infants

Prior research suggests that stress cues are particularly important for English-hearing infants' detection of word boundaries. It is unclear, though, how infants learn to attend to stress as a cue to word segmentation. This series of experiments was designed to explore infants' attention to conflicting cues at different ages. Experiment 1 replicated previous findings: When stress and statistical cues indicated different word boundaries, 9-month-old infants used syllable stress as a cue to segmentation while ignoring statistical cues. However, in Experiment 2, 7-month-old infants attended more to statistical cues than to stress cues. These results raise the possibility that infants use their statistical learning abilities to locate words in speech and use those words to discover the regular pattern of stress cues in English. Infants at different ages may deploy different segmentation strategies as a function of their current linguistic experience.     

Audio-visual priming in 7-month-old infants: An ERP study

The current study investigates categorical priming across modalities in 7-month-old infants using electroencephalographic (EEG) measures. In two experiments, infants were presented with sounds as primes, followed by images of human figures and furniture items as targets. In experiment 1 (N = 20), images were preceded by infant-directed (ID) or adult-directed (AD) speech to explore effects of intermodal categorical mismatches. Furniture targets (mismatching category) elicited an increased amplitude of the Negative central (Nc) component compared to human targets (matching category), p < .01, indicating increased attention. Results did not vary with manner of speaking (ID or AD). Experiment 2 (N = 17) explored whether a categorical mismatch between prime and target would elicit increased positive slow wave (PSW) amplitudes for human targets, indicating increased memory effort. Here, bicycle ringtones and ID speech served as primes. Again, furniture targets elicited an increased Nc regardless of prime category, p < .05, and a categorical change from human speech to furniture target images elicited an increased PSW, p < .05. No PSW effect was found for human targets following bicycle ringtones, however. The experiments reported here suggest that auditory primes may increase infant attention and memory updating particularly for non-social, categorically mismatching stimuli.     

Perception of the Ebbinghaus illusion in 5- to 8-month-old infants

The Ebbinghaus illusion is a geometric illusion based on a size-contrast between a central circle and surrounding circles. A central circle surrounded by small inducing circles is perceived as being larger than a central circle surrounded by large inducing circles. In the present study we investigated 5- to 8-month-old infants' perception of the Ebbinghaus illusion using a preferential-looking paradigm. We measured the preference between a central circle surrounded by small inducing circles (overestimated figure) and a central circle surrounded by large inducing circles (underestimated figure). Infants showed a significant preference for the overestimated figure when the central circle was flashing, but not when it was static. Furthermore, there was no preference between the two figures when the central circles were removed. These results suggest that infants' preference reflects their perception of the size illusion of the central circle. There is a possibility that 5- to 8-month-old infants perceive the Ebbinghaus illusion.     

12- and 18-month-old infants follow gaze to spaces behind barriers

Infants follow the gaze direction of others from the middle of the first year of life. In attempting to determine how infants understand the looking behavior of adults, a number of recent studies have blocked the adult's line of sight in some way (e.g. with a blindfold or with a barrier). In contrast, in the current studies an adult looked behind a barrier which blocked the child's line of sight. Using two different control conditions and several different barrier types, 12- and 18-month-old infants locomoted a short distance in order to gain the proper viewing angle to follow an experimenter's gaze to locations behind barriers. These results demonstrate that, contra Butterworth, even 12-month-old infants can follow gaze to locations outside of their current field of view. They also add to growing evidence that 12-month-olds have some understanding of the looking behaviors of others as an act of seeing.     

Object retrieval through observational learning in 8- to 18-month-old infants

Observational learning was studied in 8-, 10-, 12-, 15- and 18-month-old infants. Using object-retrieval tasks of relatively comparable difficulty for each age group, we showed that between 10 and 12 months there is a change in the capacity to learn a new skill by observation.     

Fearful faces modulate looking duration and attention disengagement in 7-month-old infants

The present study investigated whether facial expressions modulate visual attention in 7-month-old infants. First, infants' looking duration to individually presented fearful, happy, and novel facial expressions was compared to looking duration to a control stimulus (scrambled face). The face with a novel expression was included to examine the hypothesis that the earlier findings of greater allocation of attention to fearful as compared to happy faces could be due to the novelty of fearful faces in infants' rearing environment. The infants looked longer at the fearful face than at the control stimulus, whereas no such difference was found between the other expressions and the control stimulus. Second, a gap/overlap paradigm was used to determine whether facial expressions affect the infants' ability to disengage their fixation from a centrally presented face and shift attention to a peripheral target. It was found that infants disengaged their fixation significantly less frequently from fearful faces than from control stimuli and happy faces. Novel facial expressions did not have a similar effect on attention disengagement. Thus, it seems that adult-like modulation of the disengagement of attention by threat-related stimuli can be observed early in life, and that the influence of emotionally salient (fearful) faces on visual attention is not simply attributable to the novelty of these expressions in infants' rearing environment.