Task-irrelevant perceptual learning without reinforcement
Final Report Abstract
Visual perceptual learning (VPL) is defined as a long-term performance improvement on a visual task resulting from perceptual experience. Theories of VPL have assumed that performance improvements should only occur for visual features that are behaviorally relevant to an organism, either because they are pertinent to a given task (task-relevant VPL) or because they are linked to reinforcement signals (task-irrelevant VPL). According to them, task-irrelevant features are learned when diffusive neuromodulatory signals from the reward system interact with bottom-up processing of the task-irrelevant feature. This project challenged the reinforcement theory by testing whether and how task-irrelevant VPL occurs without the involvement of reinforcement signals. Three related hypotheses about the necessity of reinforcement signals for task-irrelevant VPL were tested using psychophysical learning experiments. Study 1 showed that task-irrelevant VPL of a reinforcement-paired feature was significantly enhanced in a context with perceptually close compared to distant distractor features. Thus, even very weak signals that were both subliminal and unrelated to reinforcement exerted an influence on VPL, suggesting that the outcome of VPL depends on the sensory context in which learning takes place. Study 2 tested task-irrelevant VPL in a context without reinforcement. Previous research had shown that statistically structured sources of information reflexively receive prioritized processing even in the absence of conscious awareness of the regularity. Therefore, we tested whether statistically structured events act as learning signals for co-occurring subliminal features, despite the absence of reinforcement and even stimulus salience. The results of this study confirmed that task-irrelevant VPL can occur in a purely exposure-based manner. Study 3 followed up on possible interference effects in task-irrelevant VPL. It is well known that task-relevant VPL requires a consolidation process and is usually so unstable immediately after training that it can easily be disrupted by subsequent new learning. In contrast to the typical retrograde interference effect observed in task-relevant VPL, we found an anterograde interference in task-irrelevant VPL, suggesting an involvement of at least partially distinct consolidation mechanisms in the two types of VPL. Taken together, the project results substantially advanced knowledge about the mechanisms of task-irrelevant VPL by showing that task-irrelevant learning depends both on reinforcement-based and exposure-based mechanisms. Current theories of VPL cannot explain these results and should be refined to incorporate exposure-based influences on learning.
Publications
- (2019) Perceptual learning of task-irrelevant features depends on the sensory context. Scientific reports 9 (1) 1666
Bruns, Patrick; Watanabe, Takeo
(See online at https://doi.org/10.1038/s41598-019-38586-8) - (2017). The role of auditory cortex in the spatial ventriloquism aftereffect. NeuroImage, 162, 257-268
Zierul, B., Röder, B., Tempelmann, C., Bruns, P., & Noesselt, T.
(See online at https://doi.org/10.1016/j.neuroimage.2017.09.002) - Spatial and frequency specificity of the ventriloquism aftereffect revisited. Psychological Research
Bruns, P., & Röder, B.
(See online at https://doi.org/10.1007/s00426-017-0965-4)
