Acquisition and waning of exposure–induced attraction to a nonnatural odor in rat pups

The present experiments examine acquisition and waning of exposure-induced attraction to a nonnatural odor in rat pups. I found that (1) acquisition of attraction induced by experience of an odor associated with the mother (M-E) and of attraction induced by experience of an odor in the general environment (S-E) had similar time courses and were of similar magnitude in pups less than 20 days of age; (2) waning of S-E-induced attraction to a nonnatural odor was far more rapid than waning of M-E-induced attraction; (3) M-E and S-E to an odor were less effective in pups greater than 20 days of age than in pups less than 20 days of age; and (4) although pups greater than 20 days of age receiving M-E to an odor exhibited enhanced attraction to that odor, pups of equal age receiving S-E to the same odor did not.