The other-race effect on the McGurk effect in infancy

This study investigated the difference in the McGurk effect between own-race-face and other-race-face stimuli among Japanese infants from 5 to 9 months of age. The McGurk effect results from infants using information from a speaker’s face in audiovisual speech integration. We hypothesized that the McGurk effect varies with the speaker’s race because of the other-race effect, which indicates an advantage for own-race faces in our face processing system. Experiment 1 demonstrated the other-race effect on audiovisual speech integration such that the infants ages 5–6 months and 8–9 months are likely to perceive the McGurk effect when observing an own-race-face speaker, but not when observing an other-race-face speaker. Experiment 2 found the other-race effect on audiovisual speech integration regardless of irrelevant speech identity cues. Experiment 3 confirmed the infants’ ability to differentiate two auditory syllables. These results showed that infants are likely to integrate voice with an own-race-face, but not with an other-race-face. This implies the role of experiences with own-race-faces in the development of audiovisual speech integration. Our findings also contribute to the discussion of whether perceptual narrowing is a modality-general, pan-sensory process.

The effect of familiarity on infants’ social categorization capacity

Recent studies indicate that a preference for people from one’s own race emerges early in development. Arguably, one potential process contributing to such a bias has to do with the increased discriminability of own- vs. other-race faces–a process commonly attributed to perceptual narrowing of unfamiliar groups’ faces, and analogous to the conceptual homogenization of out-groups. The present studies addressed two implications of perceptual narrowing of other-race faces for infants’ social categorization capacity. In Experiment 1, White 11-month-olds’ (N = 81) looking time at a Black vs. White face was measured under three between-subjects conditions: a baseline “preference” (i.e., without familiarization), after familiarization to Black faces, or after familiarization to White faces. Compared to infants’ a priori looking preferences as revealed in the baseline condition, only when familiarized to Black faces did infants look longer at the "not-familiarized-category" face at test. According to the standard categorization paradigm used, such longer looking time at the novel (i.e., "not-familiarized-category") exemplar at test, indicated that categorization of the familiarized faces had ensued. This is consistent with the idea that prior to their first birthday, infants already tend to represent own-race faces as individuals and other-race faces as a category. If this is the case, then infants might also be less likely to form subordinate categories within other-race than own-race categories. In Experiment 2, infants (N = 34) distinguished between an arbitrary (shirt-color) based sub-categories only when shirt-wearers were White, but not when they were Black. These findings confirm that perceptual narrowing of other-race faces blurs distinctions among members of unfamiliar categories. Consequently, infants: a) readily categorize other-race faces as being of the same kind, and b) find it hard to distinguish between their sub-categories.

Reduced perceptual narrowing in synesthesia

Synesthesia is a neurologic trait in which specific inducers, such as sounds, automatically elicit additional idiosyncratic percepts, such as color (thus “colored hearing”). One explanation for this trait—and the one tested here—is that synesthesia results from unusually weak pruning of cortical synaptic hyperconnectivity during early perceptual development. We tested the prediction from this hypothesis that synesthetes would be superior at making discriminations from nonnative categories that are normally weakened by experience-dependent pruning during a critical period early in development—namely, discrimination among nonnative phonemes (Hindi retroflex /d̪a/ and dental /ɖa/), among chimpanzee faces, and among inverted human faces. Like the superiority of 6-mo-old infants over older infants, the synesthetic groups were significantly better than control groups at making all the nonnative discriminations across five samples and three testing sites. The consistent superiority of the synesthetic groups in making discriminations that are normally eliminated during infancy suggests that residual cortical connectivity in synesthesia supports changes in perception that extend beyond the specific synesthetic percepts, consistent with the incomplete pruning hypothesis.

Audio-visual speech perception in infancy - A cross-linguistic comparison of multisensory perceptual narrowing and face-scanning behavior in languages belonging to the same rhythm class (German and Swedish)

The importance of considering speech perception and language acquisition as a multimodal phenomenon, that is to say an audio-visual phenomenon, can hardly be ignored in light of recent evidence. Research from this perspective has demonstrated that young infants are sensitive to audio-visual match in auditory (i.e. syllables, vowels and utterances) and visual (i.e. mouth movements) native and non-native speech, even when presented sequentially. Over time, as they gain more experience, infants’ perception and processing of native language attributes increases, while this sensitivity seems to decline for non-native attributes (perceptual narrowing). Empirical findings in the field of perceptual narrowing are ambiguous with regard to the beginning and the extent of this tuning phenomenon, but there is evidence that factors such as the richness and presentation of the stimuli play a crucial role. Recently, there has been renewed interest in the topic of face-scanning behavior, mainly because eye-tracking devices have made more objective and precise analyses of infants’ gaze patterns possible. Face-scanning behavior is directly associated with audio-visual speech processing, and both have an impact on infants’ future expressive language development. However, no previous study has ever examined the distance between the native and non-native language in the context of audio-visual speech processing. This is illustrated by the fact that previously studies have exclusively considered more distant languages belonging to different rhythm classes, not closer languages belonging to the same rhythm class. Languages that largely do not differ in global rhythmic-prosodic cues but for instance in more specific phonological and phonetic attributes might impact audio-visual matching and face-scanning behavior in early infancy. This influence might provide insights into how fine-grained these perception and processing mechanisms are marked during infancy, when they narrow in the direction of the infant’s native language, and which facial areas infants draw on at different time points during infancy to obtain enough (redundant) cues to acquire their native language(s). Furthermore, no previous studies have combined a longitudinal perspective on infants with a cross-linguistic view of languages in order to reduce inter-individual differences across age groups and generalize the emergence of perceptual narrowing as a cross-linguistic phenomenon. Hence, the present synopsis comprises three studies that address these perspectives on early audio-visual speech perception of languages belonging to the same rhythm class among infants by investigating early audio-visual matching sensitivities (Study 1), the occurrence of perceptual narrowing (Study 2), and face-scanning behavior during the first year of life and its impact on the infants’ future expressive vocabulary (Study 3). It summarizes the current state of the (empirical) literature in subjects such as speech perception, language discrimination and face-scanning behavior before identifying important research gaps, pointing out relevant research questions, presenting the design(s) and the main results of the three empirical studies, and finally discussing the findings and the consequential possible implications for future research and practice. The studies are based on self-collected data from the Bamberg Baby Institute at the University of Bamberg (Germany) and the Uppsala Child and Baby Lab at Uppsala University (Sweden). Whereas the first and second study were based on a cross-linguistic dataset of German and Swedish infants, the third study’s dataset consisted only of German infants who were further followed longitudinally.