Abstract
We combine audio-visual information readily in daily life. For example, in a noisy environment, what you hear is heavily weighted by what you see from reading the speaker's lips. While previous studies in adults have reported that visual information can influence the detectability of auditory information (for example, Bolognini et al., 2005; Lovelace et al., 2003; Oodgard et al., 2004), much less is known regarding the developmental trajectory of audio-visual interactions for basic, non-social and non-linguistic stimuli in infants. Here we examine whether visual information conveying no spatial information can influence infants' detectability of near threshold auditory stimuli. We adapted forced-choice preferential looking (FPL) to a gaze-contingent eye-tracking paradigm to quantify auditory detection thresholds in infants (3-8 months-olds). The auditory stimulus was a white noise sinusoidally-modulated in amplitude at 1 Hz, varying in maximum amplitude from trial to trial, presented to the left or right of central fixation. The visual stimulus modulated in brightness at 1 Hz and subtended the entire extent of the screen, thus conveying no lateralized spatial information. We quantified auditory detection thresholds, the auditory amplitude yielding 75% correct detection of the side of sound presentation, under 2 different visual conditions: (1) IP: auditory and visual information modulated in-phase and (2) OP: the visual and auditory information modulated out-of-phase. If synchronized visual information enhances auditory detection, we expect lower contrast thresholds for the IP condition relative to the OP condition. Our data in 3-8 month-olds suggests a worsening of performance, increased auditory thresholds and slower detection times, for the IP relative to OP conditions. These results complement our previous findings (Ciaramitaro & Dobkins, in preparation) in which a task irrelevant auditory stimulus conveying no spatial information impaired visual thresholds for an IP relative to OP condition, in 3- and 6-month-old infants.
Meeting abstract presented at VSS 2014