Little is known about the development of eye blinking, a spontaneous activity mediated by dopamine, from the period in-utero to six months after birth. We evaluated spontaneous eye blinking rates for eleven full-term and eleven premature infants with their mothers. Dyads were videotaped during bottle-feeding in natural context: at birth, at term (for premature infants), three months, and six months after term. Infants' and mothers' blinks were counted in a double-blind procedure.
Premature infants blinked over six times more than fetuses of similar maturational age recorded in utero in previous literature. Spontaneous blinking rates (around two blinks per minute) show no visible increase over the next six months, and no difference between the preterm and typical groups. Infants' rates contrasted with those of their mothers (around five blinks per minute) who were thus recorded under the same conditions.
Our longitudinal and ecological record confirms previous results showing low blinking rates of infants before one year. It illustrates the importance of delivery in the expression of a spontaneous behavior. It defines the typical early stage of a behavior that develops later in relation with the dopaminergic system and speech.