Development and manipulation of spontaneous eye blinking in the first year: relationships to context and positive affect.

The present study explored the development of spontaneous eye blinking (SEB) and its relationship to approach-inhibition behavior during the second half of the first year. The dopaminergic regulation of SEB in adult primates provides an empirical basis for studying blinking in infants, and dopamine's role in infant temperament provides justification for examining approach-inhibition specifically. A longitudinal design with an experimental manipulation was used to examine developmental change in the rate of SEB. Healthy, full-term infants (N = 74) were observed at 4 and 12 months. Blinking rate was observed during a quiet baseline and a randomly assigned stimulus condition. Then, approach-inhibition responses were examined as stimulus objects were presented. Experimental conditions altered blink rate at both ages, but the effects varied by age and stimulus type. At 12 months, individual differences in SEB were associated with positive affect during the approach-inhibition task. The divergent effects for the cognitive and social conditions suggest that the mechanisms regulating blink rate have distinct relationships to these behavioral domains and that these undergo changes during the first year.