Abstract
Visual perceptual learning (VPL) is a powerful tool to investigate how learning and its underlying mechanisms develop over the lifespan. Previous results with adults suggest that task-irrelevant VPL occurs only for stimuli below the perceptual threshold, because such stimuli remain undetected by attentional control and are not inhibited as task-irrelevant (Watanabe et al., 2001; Tsushima, Sasaki & Watanabe, 2006). Since attention control systems continue to develop from childhood until adulthood, children might show different task-irrelevant VPL compared with adults. To investigate this hypothesis, we examined task-irrelevant VPL in a group of elementary school children (7-10 years old, n = 20) and an adult control group (18-31 years old, n = 20). Over the course of twelve daily sessions, subjects performed a rapid-serial-visual-presentation task at the screen center, while coherent motion was presented as a task-irrelevant stimulus in the surrounding. The motion coherence level was either below or above the detection threshold. Before and after training, discrimination performance for the exposed coherent motion direction was tested. The results show that adults only improved on the direction exposed below coherence threshold as previously reported, whereas children showed improved discrimination performance irrespective of the motion coherence level during the exposure. The occurrence of task-irrelevant VPL with the above-threshold motion in children was not due to the weaker inhibition on task-irrelevant motion, because children with more pronounced selective attention ability shown by the Useful-Field-of-View test (Ball et al., 1988) tended to have greater amounts of task-irrelevant VPL. These results suggest that the mechanism of task-irrelevant VPL in children is dramatically different from that found in adults. Children may have an expanded focus of attention, allowing task-irrelevant VPL of the suprathreshold coherent motion direction together with the RSVP. Thus, the interaction between attentional control and VPL undergoes a developmental maturation from childhood to adulthood.