The roots of categorization : 4-month-old infants extract feature correlations to form audio-visual categories

• Main Author: Greuel, Alison Jeanne
• Language: English
• Published: University of British Columbia 2010
• Online Access: http://hdl.handle.net/2429/27444

Is information from vision and audition mutually facilitative to categorization in infants? Ten-month-old infants can detect categories on the basis of correlations of five attributes of visual stimuli; four- and seven-month-olds are sensitive only to the specific attributes, rather than the correlations. If younger infants can detect specific attributes of visual stimuli, is there a way to facilitate the perception of these attributes as a meaningful correlation, and hence, as a category? The current studies investigate whether integrating information from two domains—speech within the auditory system together with shapes in the visual domain—could facilitate categorization. I hypothesized that 4-month-old infants could categorize audio-visual information by pairing correlation-based stimuli in the auditory domain (monosyllables) with correlation-based stimuli in the visual domain (line-drawn animals). In Experiment 1, infants were exposed to a series of line-drawn animals whose features were correlated to form two animal categories. During test, infants experienced three test trials: a novel member of a previously-shown category, a non-member of the categories (that shared similar features), and a completely novel animal. Experiment 2 used the same animals and paradigm, but each animal was presented with a speech stimulus (a repeating monosyllable) whose auditory features were correlated in order to form two categories. In Experiment 3, categorization of the auditory stimuli was investigated in the absence of the correlated visual information. Experiment 4 addressed some potential confounds of the findings from Experiment 2. Results from this series of studies show that 4-month-olds fail categorize in both visual-only and auditory-only conditions. However, when each visual exemplar is paired with a corresponding, correlated speech exemplar, infants can categorize; they look longer at a new, within-category exemplar than a new, category violator. These findings provide evidence that infants extract correlated information from two domains, enabling cross-modal categorization at a very young age. Infants’ sensitivity to correlated attributes across two domains and the implications for categorization are discussed.