Long-term retention of a conditioned taste aversion in preweanling and adult rats

Abstract

The retention and extinction of a conditioned taste aversion after either short (6-day) or long (60-day) intervals was investigated in preweanling (I8-day-old) and adult rats. Taste-only and illness-only control conditions were employed, as were variations in the concentration of the US (holding Liel amount constant). Results indicated that after the short retention interval, retention of the taste aversion was equivalent for both ages. After the long interval, however, the I8-day-old rats exhibited significantly weaker taste aversion than their adult counterpartsinfantile amnesia. Manipulation of US concentration had no effect on the magnitude of the taste aversions for either age or retention interval. The results are discussed in terms of their implications for infantile amnesia and general laws of learning.Immature animals forget at a faster rate than do more mature animals (for reviews, see Campbell & Campbell & Spear, 1972;Spear, 1978Spear, , 1979, and this probably is also true for humans (Cohen & Gelber, 1975;Levy, 1960;Pancratz & Cohen, 1970). This accelerated rate of forgetting by younger organisms has been termed infantile amnesia. However, some recent evidence suggests that less infantile amnesia may occur when the information to be retained involves a particular class of events that may constitute a "highly prepared" association (Coulter, Collier, & Campbell, 1976;Spear, 1978). Ontogenetic studies of conditioned taste aversion (Campbell & Alberts, 1979; Klein, Mikulka, Domato, & Hallstead, 1976) provide some of the more convincing of this evidence.While long-term retention of taste-illness associations by adults is excellent (Biederman, Milgram, Heighington, Stockman, & O'Neil, 1974;Dragoin, Hughes, Devine, & Bentley, 1973), the data with respect to immature organisms are mixed. Specifically, Klein et al. (1976), using postweanling rats (23-dayold), and Campbell and Alberts (1979), who used preweanling (18-day-old) infant rats, have demonstrated retention equivalent to that of adults over retention intervals of 28 and 56 days. However, with rat pups 10 and 12 days of age, Campbell and Alberts (1979) did find poorer retention across long intervals. Both of these studies used LiCI as the unconditioned stimulus (US) and employed a singlebottle testing procedure. The data obtained with Preparation of this article was supported by grants from the National Science Foundation (BNS 74-24194 and BNS 78-02360) to the third author. We thank Norman "Richter for technical advice and assistance and Teri Tanenhaus for preparation of the manuscript. Requests for reprints should be sent to Norman E. Spear, Department of Psychology, State University of New York at Binghamton, Binghamton, New York 13901. these procedures suggest that, by 18 days of age, rat pups have attained adult levels of retention for a taste-illness association. In contrast to the findings of Campbell and Alberts (1979), Ader and Peck (1977) and Peck (Note 1) have reported relatively poor retention of all early (Zl-day-old rat pup) taste-ill...

The effects of flavor preexposure and test interval on conditioned taste aversions in rats

“…This would suggest that forgetting occurred among nonpreexposed subjects tested over an extended interval. This result is inconsistent with previous failures to note any forgetting of conditioned taste aversions (Dragoin, Hughes, Devine, & Bentley, 1973;Kalat, 1977;Steinert, Infurna, & Spear, 1980). This forgetting could have resulted from the control subjects' acquiring relatively weak aversions which gradually diminished over the 21-day interval.…”

Increase in retention of a taste aversion by weanling rats after a long interval

“…This explanationwould predict that the manifest strength of taste aversions in younger animals should generally increase over time. This idea seems to be inconsistent with the more rapid forgetting of taste aversions that has been found in other studieswith young rats (Schweitzer & Green, 1982;Steinert, Infurna, & Spear, 1980).It shouldbe noted, however, that in these studies the aversions were relatively strong when tested after a short retention interval. It remains possible that when the expressed aversion is initially weak:, as was the lings were randomly divided into six groups (n= 10).…”

Preference for familiar humans by rats

“…With few exceptions, early studies reviewed by Munn (1950) involve simple tasks (e.g., conditioned fear responses) and intertest intervals ranging from several hours to weeks. More recent studies, including those involving discrimination learning, continue to involve relatively briefretention intervals (e.g., Calhoun & Handley, 1973;Henderson, 1978;Steinert, Infurna, & Spear, 1980), although there is evidence of rats retaining associative learning for periods as long as 12 or 18 months (Davis & Bradford, 1986). To determine whether the preference for a familiar handler could be retained for an extended period of time, the subjects from Experiment 1 were retested following a 5-month period.…”