Abstract
In the very early training stages of many perceptual tasks, an observer is uncertain about the specifics (e.g., size, orientation) of the signal and occasionally an observer's performance will get worse over a number of trials before starting to improve. What causes this effect? We investigate this effect using a rapid perceptual learning paradigm (RPL; Abbey et al., VSS, 2001). In RPL paradigm used in this study, sessions consisted of sets of 4 learning trials. At the beginning of a learning set, 1 of 4 possible targets (elongated oriented Gaussians) were randomly chosen and used throughout the set. On each trial, the target appeared randomly at one of 8 locations in visual noise. The observer's task was to localize the target. At the end of the 4th learning trial of each set, the observer also had to identify the target. The RPL paradigm allows to compare the amount of learning in humans to that of an optimal Bayesian observer which updates the weightings assigned to the perceptual templates as the learning trials progress. We investigated how the learning is affected by the observer's correct or incorrect identification of the target at the end of the 4th learning trial. All three observers studied showed an improvement in localization performance with learning trial number for the learning sets with correct target identification (∼ 8.7 % from the 1st to the 4th learning trial) and also across all learning sets (∼ 7%). However, learning sets in which the observers incorrectly identified the target resulted in a decrease in localization performance (∼ 8 %). These results suggest that when an observer is uncertain about the signal, occasionally the external noise (and potentially internal noise) provides the observer with evidence for the presence of an erroneous target. This causes the observer to monitor the incorrect template (as evidenced by the incorrect target identification) and produces negative learning.
Support: NIH-RO1 53455 , NASA NAG 9-1157