Abstract:
Directed forgetting occurs when individuals recall stimuli that are designated to be remembered better than stimuli that are designated to be forgotten. The current study investigated the effects of cues that signal to remember or forget on initial discriminability and rate of forgetting in the exponential decay model of memory. In Experiment 1, we trained pigeons on a delayed symbolic-matching to sample (DSMTS) procedure in which color samples matched a left or right comparison key. In Experiment 2, we trained pigeons on a DSMTS procedure in which color samples matched a different color comparison key that was randomized across the left and right keys. The length of the retention interval in both experiments ranged from 0.5 s to 20 s. During training, we introduced two different cues before the retention intervals; cues to either remember or forget the sample stimuli (R-cues and F-cues, respectively). R-cues indicated the occurrence of comparison stimuli, whereas F-cues indicated the nonoccurrence of comparison stimuli. During testing, we introduced probe trials in which F-cues were followed by the comparison stimuli; however, correct responses were not reinforced. In general, both experiments showed that matching accuracies decreased with longer retention intervals as opposed to shorter retention intervals. In both experiments, initial discriminability was lower in F-cued probe trials than R-cued trials. While the rate of forgetting did not vary across the cued stimuli in Experiment 1, rate of forgetting was faster after F-cued probes than after R-cued stimuli in Experiment 2. These findings suggest that when the location of the comparison stimuli is predictable, the 'directed forgetting effect' may be less systematic due to mediated matching performance.