ONTOGENY OF LONG-TERM-MEMORY FOR LEARNED TASTE-AVERSIONS

Eighteen-day-old and adult rats were trained on a learned taste-aversion (illness reinforced) or a lick-suppression (shock reinforced) task and tested for retention after either 1, 28, or 56 days. Young rats showed a retention deficit relative to adults in the lick-suppression task but not for taste-aversion learning. Young rats did, however, show relatively less suppression to the saline solution than adult, but a follow-up experiment showed that changing the poisoned solution to a more-distinctive flavor produced high levels of suppression and no retention deficit in 18-day-old rats. In the final experiment a technique was developed for studying retention of taste aversion in suckling rats. Retention of taste aversion was studied in 10-, 12-, 15-, and 20-day-old rats at retention intervals ranging from 1 to 10 days. Using this procedure the younger (10- and 12-day-old) rats showed more rapid forgetting than 15- or 20-day-olds. These findings were interpreted as (1) evidence for a dissociation of memory for learned taste aversions from other kinds of learning and (2) further support for the general proposition of improved long-term memory during early ontogenesis. © 1979 Academic Press, Inc.