DEVELOPMENT OF EXPLORATION AND INVESTIGATION IN THE NORWAY RAT (RATTUS-NORVEGICUS)

A cross-sectional study of the development of spontaneous exploratory behavior in the laboratory rat was conducted. Long-Evens hooded rat pu ps aged 11 to 28 days (n = 158, from 25 litters) were placed into a di mly illuminated arena far 10 min on 2 consecutive days. Analysis of vi deotaped records from the second session for each rat pup showed a rel atively sudden emergence of locomotor exploration between 12 and 16 da ys of age. The behavioral topography of interactions with objects deve loped less uniformly, with some features (e.g., bout length) relativel y unchanging and other features (e.g., number of bouts, number of diff erent behaviors displayed) increasing with age, The data for locomotor exploration are consistent with an explanation that depends on matura tion-driven emergence of species-typical behavior, but that explanatio n cannot account for the pattern of development for object investigati on. These results provide further evidence that some important aspects of the character of exploratory behavior depend, at least partially, on experience, and that exploration is not in fact a single behavior s ystem. In addition, they provide important baseline information for fu rther studies of the structure and function of exploratory behavior.