Fig. 1.

Experimental methods. (a) Time line of longitudinal study. (b) Sequential steps in neonatal novelty exposure. (i) Removal of dam from home cage. (ii) Transfer of Novel pups to individual nonhome cages. (iii) Return of Novel pups to home cage after 3-min exposure to nonhome cages. (iv) Return of dam to entire litter in home cage. Experimenter handling and duration of maternal separation were matched between Novel (N) and Home (H) pups. (c) Setup for social competition testing. After individual training, pairs of rats competed for access to a chocolate reward at the end of the runway. (d) Setup for observation of postnovelty exposure pup retrieval. The middle two compartments were used as buffer zones for better separation of Novel and Home pups.