Early experience with the artificial nipple.

The present study examined the newborn pup's responsiveness to artificial nipples that differed in length and width. In a series of experiments, pups were: exposed to a long (5.0 mm), thin (1.0 mm) nipple or a short (2.0 mm), fat (2.5 mm) nipple and their immediate behavioral responses including oral grasping were recorded and quantified (Experiment 1); preexposed to one artificial nipple and then reexposed to another artificial nipple to determine how early nipple experience affected subsequent responding to the artificial nipple (Experiment 2); videotaped to characterize details of oral grasping and to develop a technique for measuring depth of nipple entry into the pup's mouth (Experiment 3a); provided early nipple experience to see how depth of nipple entry into the pup's mouth changed when pups were reexposed to another artificial nipple (Experiment 3b); and exposed to an artificial nipple to determine how early nipple experience changed the pattern of oral grasping and ingestion of milk from a surrogate nipple (Experiment 4).