Tift, Amy H.

Lewkowicz & Hansen-Tift found that when 4-month-old infants see and hear a person
talking, they look more at her eyes but that 8- and 10-mo infants look more at her mouth. The
developmental attentional shift to the mouth reflects infants’ growing interest in speech.
Attention to the mouth enables infants to gain access to redundant and maximally salient
audiovisual cues which then facilitate speech and language acquisition.
We investigated the separate role of mouth movement and vocalization cues in the attentional
shift from a talker’s eyes to the talker’s mouth. In 3 experiments, we used an eye-tracker to
measure the proportion of attention infants, 4-, 8-, and 10-mo, allocate to the eyes and mouth of a
static/silent face, a static/talking face, and a silently talking face. We found that when infants see
a static person, they attend to the eyes. Lewkowicz & Hansen-Tift found that when infants see
and hear a person talking, 4-mos look at the eyes whereas 8- and 10-mos look at the mouth.
When infants see a silently talking person, only 10-mos look at the mouth. These findings
demonstrate that the shift from the eyes to the mouth is mediated by three factors: dynamic
visual speech cues, an emerging interest in speech, and the redundancy of audiovisual speech.
Thus, younger infants are not interested in speech so they focus on the eyes, whereas older
infants become interested in speech, shifting their focus to the mouth, but initially at 8 m, this
shift requires that speech be multisensory.

From syllables to fluent speech, it is important for infants to quickly learn and decipher linguistic information. To do this, infants must not only use their auditory perception but also their visual perception to understand speech and language as a multisensory coherent event. Previous research by Lewkowicz and Hansen-Tift (2012) demonstrated that infants shift their allocation of visual attention from the eyes to the mouth of the speaker's face throughout development as they become interested in speech production. This project examined how infants, from 4-14-months of age, allocate their visual attention to increasingly complex speech tasks. In Experiment 1, infants were presented with upright and inverted faces vocalizing syllables and the results demonstrated that in response to the upright faces, 4-month-old infants attended to the eyes and 8- and 10-month-olds attended equally to the eyes and mouth. In response to the inverted face presentation, both the 4- and 10-month-olds attended equally to the eyes and mouth but the 8-month olds attended to the eyes. In Experiment 2, infants were presented with a phoneme matching task (Patterson & Werker, 1999, 2002, 2003) and the results demonstrated that the 4-month-old infants successfully matched the voice to the corresponding face, but that older infants did not. Measures of their selective attention to this task showed that the 4-month-old infants attended more to the eyes of the faces during the task, not attending to the redundant speech information at the mouth, but older infants attended equally to the eyes and mouth, although they did not match the voice to the face. Experiment 3 presented infants with a fluent speech matching task (Lewkowicz et al., 2015) which demonstrated that although the infants (12-14-months) did not systematically match the voice to the corresponding face, the infants attended more to the mouth region, which would have provided them with the neces sary redundant information. Overall, these studies demonstrate that there are developmental changes in how infants distribute their visual attention to faces as they learn about speech and that the complexity of the speech is a critical factor in how they allocate their visual attention.

Speech perception plays an important role in how infants begin to produce speech. This study aims to understand how changes in infant selective attention to various parts of talking faces guides their understanding of speech and subsequent production. In this study, we tracked infant (4-12 months of age) and adult gaze patterns to determine where on a face they attend, when hearing and seeing the face speak in either their native (English) or a non-native language (Spanish). We also tracked infant selective attention to moving-silent and silent-static faces, to determine if this would result in different patterns of attention. The findings suggest that there are two shifts in infant attention. The first shift occurs between four and eight months of age, with infants shifting their eyes to the mouth of the talking face. The second shift occurs around twelve months of age, when infants begin to return their gaze back to the eye region when hearing and seeing their native language, but continue to attend to the mouth region when hearing and seeing the non-native language. Overall, the results of this study suggest that changes in selective attention to talking faces guides the development of speech production and is dependent on early language experience.