Acquisition and reversal of a discriminated autoshaped response in male and female rats: Effects of long or short and fixed or variable intertrial interval durations

Groups of male and female Wistar rats were exposed to autoshaping procedures in which the duration (50 vs 20 s) and the variablity (fixed vs variable) of the intertrial interval were manipulated. Pellet delivery occurred after one of the levers (CS+) had been presented for 10 s. Presentation of the other lever (CS−) was not associated with pellet delivery. CS+ contacts occurred more frequently and at higher rates when the intertrial interval was 50 s than when it was 20 s, while intertrial interval variability did not play an important role. Males contacted CS+ and CS− more frequently and at a higher rate than did females. Goal-directed activity (nose pokes in feeder tray) occurred more often when the intertrial interval was short than when it was long. Females showed higher goal-directed activity than did males, both during CS presentation and during the intertrial interval. When experimental contingencies were reversed, CS+ contacts decreased and CS− contacts increased for males and females, but the decrease in CS+ contacts occurred more slowly for males than for females. The results of these experiments add to a growing body of literature suggesting the existence of fundamental behavioral differences between the sexes. These differences are partly attributable to the influence of gonadal hormones during development and maturation and partly attributable to the behavioral requirements of the experimental procedures.