The phenomenon of task-irrelevant perceptual learning

Abstract

Task-irrelevant perceptual learning (TIPL) has captured a growing interest in the field of perceptual learning. The basic phenomenon is that stimulus features that are irrelevant to a subject's task (i.e. convey no useful information to that task) can be learned due to their consistent presentation during task-performance. Here we review recent research on TIPL and focus on two key aspects of TIPL; (1) the mechanisms gating learning in TIPL, and (2) what is learned through TIPL. We show that TIPL is gated by learning signals that are triggered from task processing or by rewards. These learning signals operate to enhance processing of individual stimulus features and appear to result in plasticity in early stages of visual processing. Furthermore, we discuss recent research that demonstrates that TIPL is not in opposition to theories of attention but instead that TIPL operates in concert with attention. Where attentional learning is best to enhance (or suppress) processing of stimuli of known task relevance, TIPL serves to enhance perception of stimuli that are originally inadequately processed by the brain.

Figure 1

Schematic of mechanisms found to be involved in TIPL. TIPL consists of mechanisms gating learning (top), which are thought to be high-level stages of processing, and, changes in the sensory processing (bottom), which are thought to be low-level stages of processing. A task-relevant stimulus can trigger the release of learning signals that promote learning of both task-relevant and task-irrelevant stimuli (c.f. Seitz and Watanabe, 2003). Task-relevant stimulus processing can also trigger attentional selection that inhibits learning of task-irrelevant stimuli and promotes learning for task-relevant stimuli (c.f. Tsushima, Seitz and Watanabe, 2008; Chou, Seitz and Watanabe, in press). Learning signals can also be released through other processes such as delivery of rewards (c.f. Seitz, Kim and Watanabe, 2009).