Abstract
PURPOSE: In the change detection task used stimuli with foreground- background segmentation, the performance for the foreground change detection was better than that of the background change detection. Therefore, it has been indicated that attention tended to direct the foreground elements (Turatto, Angrilli, Mazza, Umilta, &, Driver, 2002; Mazza, Turatto, & Umilta, 2005). However, it is controversial whether attention is always directed toward the foreground selectively or attentional allocation is influenced by the probability of change. The present study explores the influence of manipulating the probability of changes on attentional allocation with foreground- background segmentation. METHODS: The change detection task used stimuli consisted of the foreground and the background elements was performed. Participants responded whether the foreground or the background changed or not. We set 2 conditions; in one condition, the foreground change was 50% and the background change was 50% (50%– 50% condition), in the other condition, the foreground change was 20% and the background change was 80% (20%– 80% condition). 2 blocks of experimental trials were presented to the participants. On the first block, information about the change was not given to the participants (Default attention). On the second block, participants were informed that the change could occur either the foreground or the background (Divided attention). RESULTS & CONCLUSIONS: When information about the change was not given, accuracy of the foreground change was higher than that of the background change in both probability conditions. However, when attention was divided, accuracy of the background change is higher than that of the foreground change in 20%– 80% condition. The results suggest that the selective attention was not always allocated to the foreground, but the amount of attentional allocation is controlled according to the situational factor such as the probability of change.