Semantic comprehension in infancy: a signal detection analysis.

The purpose of this study was to validate a paradigm by which an infant's comprehension of concrete nouns could be assessed while controlling for (a) response bias, (b) stimulus preference, and (c) maternal cuing. More specifically, we sought to determine whether 11- and 13-month-old infants directed their eye fixations to the referent of an object word said by the mother and to determine whether there was a developmental shift in responding to object words at these 2 ages, as some previous research suggests. Duration of looking at each of 4 corners of an apparatus was measured while the mother (unable to see what the child was doing) uttered a word she felt the infant knew, 1 she felt he/she did not know, and a nonsense word. Analyses based on signal detection theory using "known" words as signal trials and nonsense words as noise revealed that 13-month-olds directed their looking time significantly longer at the referent of the known word when that word was uttered than when the nonsense word was uttered. At neither age did looking at the referent of the unknown word exceed control values. No significant effects were obtained at 11 months of age, nor were there any sex effects.