Infants’ intermodal perception of numerosity in an experimental study with objects and socially salient stimuli

Abstract

In the present cross-sectional experimental study we investigated infants’ early ability to intermodally detect numerosity of visual-auditory object-like and social stimuli. We assumed that presentation of face – voice stimuli would distract infants’ attention from detection of numerical invariant. Seventy-eight infants (aged 5, 7 and 9 months) participated in four experimental Conditions (simultaneously projected pairs of identical objects, non-identical objects, objects projected together with familiar face and objects projected together with unfamiliar face). Visual stimuli in each trial varied in numerosity (1 -2 / 1-3 / 2 -3) and they were accompanied by piano sounds or voice sounds also varying in numerosity (one, two or three sounds in La tonality). By means of preferential looking technique, we measured infants’ fixation of attention to the visual stimulus that numerically matched with the sound. When object-like stimuli were projected, infants –except 5-month-old boys –tended to intermodally detect numerical invariant. Shape similarity of the objects facilitated infants’ intermodal detection of numerosity. When socially salient stimuli were co-presented with object-like stimuli, infants preferred to look at the face, ignoring numerosity of the auditory stimulus. Nor sound quality (piano vs. voice) neither familiarity of the face (mother’s face vs. stranger woman’s face) affected infants’ perception. Although intermodal detection of perceptual cues is a primary function of both face and number perception, each one of these perceptual systems seems to follow a different developmental path.

Keywords

• Infant development
• Intermodal perception
• Face-voice perception
• Detection of numerosity