The role of external feedback and internal reward in Perceptual learning of 4AFC orientation discrimination task

Abstract

Both external feedback (e.g. auditory) and internal reward signal (e.g. introduction of an easy task) can facilitate perceptual learning, providing evidence for supervised and Hebbian learning rules in PL. Characteristics of these two learning mechanisms remained unanswered. In the current study, we trained six groups of subjects to learn a 4-Alternative forced-choice (4-AFC) grating orientation discrimination task that differed in types of feedback (no, auditory, and full feedback) and performance accuracy (two staircases converge to 35% correct, one staircase converges to 35% and the other 70%) to examine the learning benefits from feedback and high accuracy. While auditory feedback just indicated the correctness of each response, full feedback included a tone to indicate correct response and a re-displayed grating of correct orientation, which provided complete information. The results showed that: 1) Thresholds decreased for all 6 groups as training proceeded; 2) External feedback prompt learning gradually with information carried by feedback increased; 3) Adding easy task (i.e. 70% correct) improved performance significantly, showing the benefit of internal reward; 4) Interaction of external feedback and internal reward was observed in some but not all conditions, manifesting the flexibility of system employment of different information to optimize perceptual performance. A potential hybrid model will also be discussed.