Lip Movement Exaggerations During Infant-Directed Speech

Abstract

Purpose Although a growing body of literature has indentified the positive effects of visual speech on speech and language learning, oral movements of infant-directed speech (IDS) have rarely been studied. This investigation used 3-dimensional motion capture technology to describe how mothers modify their lip movements when talking to their infants. Method Lip movements were recorded from 25 mothers as they spoke to their infants and other adults. Lip shapes were analyzed for differences across speaking conditions. The maximum fundamental frequency, duration, acoustic intensity, and first and second formant frequency of each vowel also were measured. Results Lip movements were significantly larger during IDS than during adult-directed speech, although the exaggerations were vowel specific. All of the vowels produced during IDS were characterized by an elevated vocal pitch and a slowed speaking rate when compared with vowels produced during adult-directed speech. Conclusion The pattern of lip-shape exaggerations did not provide support for the hypothesis that mothers produce exemplar visual models of vowels during IDS. Future work is required to determine whether the observed increases in vertical lip aperture engender visual and acoustic enhancements that facilitate the early learning of speech.

Visual speech segmentation: using facial cues to locate word boundaries in continuous speech

“…It has been suggested that newborn infants have a preference for attending to faces (Goren, Sarty, & Wu, 1975; Morton & Johnson, 1991; Simion, Valenza, Macchi-Cassia, Turati, & Umilta, 2002). Furthermore, adults pattern their input to infants to enhance facial cues, exaggerating visual prosodic cues during infant-directed speech (Green, Nip, Wilson, Mefferd, & Yunusova, 2010). Facial cues therefore likely provide an early, salient cue to linguistic structure.…”

Asymmetry in infants' selective attention to facial features during visual processing of infant-directed speech

“…In contrast, other work has shown that infants continue to distribute fixations more to talkers' eyes and upper part of the face (Liu et al, 2011). Examinations of mothers' speech productions have shown distinct facial characteristics and exaggerated lip movement in ID speech (Shochi et al, 2009; Green et al, 2010; Shepard et al, 2012). …”

Longitudinal Development of Speech Motor Control: Motor and Linguistic Factors

“…Most vowel contrasts in English can be approximated by modeling two components (Fromkin, 1964): vertical opening and horizontal spread. Studies of lip movements have revealed that, during the production of English vowels, lip shape is largely driven by the vertical opening (Fromkin, 1964; Green, Nip, Wilson, Mefferd, & Yunusova, 2010). Of course, horizontal spreading and rounding is also prominent for a small number of vowels (Fromkin, 1964; Stevens, 2000) and consonants (e.g., /w/; Chomsky & Halle, 1968; Stevens, 2000).…”