EFFECTS OF VARYING TRIAL DISTRIBUTION, INTRAMAZE AND EXTRAMAZE CUES, AND AMOUNT OF REWARD ON PROACTIVE-INTERFERENCE IN THE RADIAL MAZE

Rats are typically less accurate in their arm selections in the radial maze over successive trials in a session (Roberts & Dale, 1981). In t he present study, rats' choice accuracy declined when such trials were separated by 2-min (massed) but not by 2-h (spaced) intertrial interv als. Changing intramaze visual/tactile arm stimuli (Experiments 1 and 3) or extramaze landmark stimuli (Experiment 4) between trials weakene d the massed-trials effect, but changing the number of food pellets pe r arm, either alone or in conjunction with changes in intramaze cues ( Experiments 2 and 3), did not. The rats also tended to avoid the spati al locations of their last four choices on a previous trial during the ir first four choices on a current trial, and more so with massed than with spaced trials. These findings indicate that intertrial proactive interference (PI) occurred only with massed trials and was weakened b y changing intra- and extramaze cues between such trials.