Direction of gaze and emergence of speech in the second year.

Orienting to the right member of a pair of identical pictures increased monotonically with age in a longitudinal sample of 14 infants seen monthly from 13 to 22 months. The magnitude of the correlation between this orientation bias and a measure of language development also rose with age reaching a peak at 20 months and then declining. It was suggested that the acceleration of vocabulary and maturational changes in the central nervous system that occur between 16 and 22 months are associated with a special excitatory state in the temporal cortex of the left hemisphere.