Cryptopsychobiology: the appearance, disappearance, and reappearance of a species-typical action pattern during early...

Late in gestation, intraoral infusion of lemon elicits a facial wiping response from rat fetuses. This facial wiping response is isomorphic with that of older pups and adult rats exposed to aversive oral stimulation. Most studies of the postnatal development of aversive responses have demonstrated that facial wiping does not appear in the repertoire of rat pups until the second postnatal week. In certain test situations, however, wiping can be elicited from neonatal rats. This fact suggests that the expression of facial wiping by neonates is constrained or facilitated by the environmental conditions present at the time of testing. In this report, a series of seven experiments is described that document the wiping response of rat fetuses and pups in age-typical environments, and an environmental constraint hypothesis is examined. Examination of the ontogeny of facial wiping in this manner highlights issues that should be addressed in studies of behavioral continuity between the prenatal and the postnatal periods.