When is old better? Task Irrelevant Perceptual Learning with older people
33.502, Sunday, May 12, 8:30 am - 12:30 pm, Vista Ballroom
Li-Hung Chang1, 2, Kazuhisa Shibata1, Yuko Yotsumoto3, John Andersen4, Yuka Sasaki1, Takeo Watanabe1; 1Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, 2Department of Psychology, Boston University, 3Department of Life Sciences, The University of Tokyo, 4Department of Psychology, University of California, Riverside
Visual perceptual learning (VPL) is defined as long-term improvement on a visual task after visual experience. We found that VPL of a task-irrelevant feature (task-irrelevant VPL, or TIVPL) occurs when the feature signal was around the threshold but not when it was suprathreshold (Tsushima et al, 2009). We have suggested that the reason for the differential results is that while the attentional control system detects and inhibit suprathreshold task-irrelevant signals, it fails to detect and thus to inhibit subthreshold signals (Tsushima, Sasaki & Watanabe, 2006). If this is true, TIPL should occur with some suprathreshold irrelevant signals with older people, since older people tend to have weaker inhibitory controls. In order to test this hypothesis, we conducted 8 days of training during which older subjects (n=8, 67-77 yr) were asked to perform RSVP tasks while coherent motion was presented in the background as a task-irrelevant feature. The exposed coherent motion ratio (strength) was varied from trial to trial so that on some trials the presented coherent motion was subthreshold and on other trials it was suprathreshold. A certain motion ratio was always paired with the same coherent motion direction. Before and after the training, we measured performance in the detection of coherent motion directions to examine the magnitudes of TIVPL of subthreshold and suprathreshold motion coherent motion directions. The results indicate that TIVPL with older subjects occurred not only with suprathrshold coherent motion but also with the subthreshold coherent motion with which TIVPL was not observed with younger subjects. These results are in accord with the hypothesis that older people have a smaller degree of inhibitory control than younger people, which allowed TIVPL to occur with suprathrshold task-irrelevant coherent motion.