Infants' Mapping of New Faces to New Voices

Object labeling and disambiguation in 4-month-old infants

The account that word learning starts in earnest during the second year of life, when infants have mastered the disambiguation skills, has recently been challenged by evidence that infants during the first year already know many common words. The preliminary ability to rapidly map and disambiguate linguistic labels was tested in Italian-speaking infants (N = 96, 47 boys; age = 4 and 6 months, eye tracking). Infants can rapidly map linguistic labels to objects and movements, and disambiguate the intended referents to novel words, but they fail with sinewave analogs. In hearing infants, mapping and disambiguation emerge early in development, and are flexible as to which visual referents infants are willing to map to linguistic labels, but may be constrained to linguistic sounds.

Young children's attributes are better conveyed by voices than by faces

The purpose of this study was to explore how young children's vocal and facial cues contribute to conveying to adults important information about children's attributes when presented together. In particular, the study aimed to disentangle whether children's vocal or facial cues, if either, are more dominant when both types of cues are displayed in a contradictory mode. To do this, we assigned 127 college students to one of three between-participants conditions. In the Voices-Only condition, participants listened to four pairs of synthetized voices simulating the voices of 4-5-year-old and 9-10-year-old children verbalizing a neutral-content sentence. Participants needed to indicate which voice was better associated with a series of 14 attributes organized into four trait dimensions (Positive Affect, Negative Affect, Intelligence, and Helpless), potentially meaningful in young child-adult interactions. In the Consistent condition, the same four pairs of voices delivered in the Voices-Only condition were presented jointly with morphed photographs of children's faces of equivalent age. In the Inconsistent condition, the four pairs of voices and faces were paired in a contradictory manner (immature voices with mature faces vs. mature voices with immature faces). Results revealed that vocal cues were more effective than facial cues in conveying young children's attributes to adults and that women were more efficient (i.e., faster) than men in responding to children's cues. These results confirm and extend previous evidence on the relevance of children's vocal cues to signaling important information about children's attributes and needs during their first 6 years of life.

Learning how to learn from social feedback: The origins of early vocal development

Infants' prelinguistic vocalizations reliably organize vocal turn-taking with social partners, creating opportunities for learning to produce the sound patterns of the ambient language. This social feedback loop supporting early vocal learning is well-documented, but its developmental origins have yet to be addressed. When do infants learn that their non-cry vocalizations influence others? To test developmental changes in infant vocal learning, we assessed the vocalizations of 2- and 5-month-old infants in a still-face interaction with an unfamiliar adult. During the still-face, infants who have learned the social efficacy of vocalizing increase their babbling rate. In addition, to assess the expectations for social responsiveness that infants build from their everyday experience, we recorded caregiver responsiveness to their infants' vocalizations during unstructured play. During the still-face, only 5-month-old infants showed an increase in vocalizing (a vocal extinction burst) indicating that they had learned to expect adult responses to their vocalizations. Caregiver responsiveness predicted the magnitude of the vocal extinction burst for 5-month-olds. Because 5-month-olds show a vocal extinction burst with unfamiliar adults, they must have generalized the social efficacy of their vocalizations beyond their familiar caregiver. Caregiver responsiveness to infant vocalizations during unstructured play was similar for 2- and 5-month-olds. Infants thus learn the social efficacy of their vocalizations between 2 and 5 months of age. During this time, infants build associations between their own non-cry sounds and the reactions of adults, which allows learning of the instrumental value of vocalizing.

Should I learn from you? Seeing expectancy violations about action efficiency hinders social learning in infancy

Infants generate basic expectations about their physical and social environment. This early knowledge allows them to identify opportunities for learning, preferring to explore and learn about objects that violate their prior expectations. However, less is known about how expectancy violations about people's actions influence infants' subsequent learning from others and about others. Here, we presented 18-month-old infants with an agent who acted either efficiently (expected action) or inefficiently (unexpected action) and then labeled an object. We hypothesized that infants would prefer to learn from the agent (label-object association) if she previously acted efficiently, but they would prefer to learn about the agent (voice-speaker association) if she previously acted inefficiently. As expected, infants who previously saw the agent acting efficiently showed greater attention to the demonstrated object and learned the new label-object association, but infants presented with the inefficient agent did not. However, there was no evidence that infants learned the voice-speaker association in any of the conditions. In summary, expectancy violations about people's actions may signal a situation to avoid learning from them. We discussed the results in relation to studies on surprise-induced learning, motionese, and selective social learning, and we proposed other experimental paradigms to investigate how expectancy violations influence infants' learning about others.

Learning to Recognize Unfamiliar Voices: An Online Study With 12- and 24-Month-Olds

Young infants are attuned to the indexical properties of speech: they can recognize highly familiar voices and distinguish them from unfamiliar voices. Less is known about how and when infants start to recognize unfamiliar voices, and to map them to faces. This skill is particularly challenging when portions of the speaker’s face are occluded, as is the case with masking. Here, we examined voice−face recognition abilities in infants 12 and 24 months of age. Using the online Lookit platform, children saw and heard four different speakers produce words with sonorous phonemes (high talker information), and words with phonemes that are less sonorous (low talker information). Infants aged 24 months, but not 12 months, were able to learn to link the voices to partially occluded faces of unfamiliar speakers, and only when the words were produced with high talker information. These results reveal that 24-month-old infants can encode and retrieve indexical properties of an unfamiliar speaker’s voice, and they can access this information even when visual access to the speaker’s mouth is blocked.

Disjunctive inference in preverbal infants

Can preverbal infants utilize logical reasoning such as disjunctive inference? This logical operation requires keeping two alternatives open (A or B), until one of them is eliminated (if not A), allowing the inference: B is true. We presented to 10-month-old infants an ambiguous situation in which a female voice was paired with two faces. Subsequently, one of the two faces was presented with the voice of a male. We measured infants' preference for the correct face when both faces and the initial voice were presented again. Infant pupillary response was measured and utilized as an indicator of cognitive load at the critical moment of disjunctive inference. We controlled for other possible explanations in three additional experiments. Our results show that 10-month-olds can correctly deploy disjunction and negation to disambiguate scenes, suggesting that disjunctive inference does not rely on linguistic constructs.