Abstract
The goal of this study was to examine the conditions under which an abrupt onset captures attention, and by doing so to determine whether explanations based on dynamic transients or new objects better account for the onset capture effect. If the transient change caused by an onset stimulus is the reason for its capturing attention, the capture effect should be modulated by the amount of transient changes. The new-object account, however, predicts no effect caused by these transient changes. We used an Inattentional Blindness (IB) task, in which a color task was designed for the participants to develop the attentional set for color, and an unexpected onset was used in the inattention trial to probe the effect of attentional capture by the onset. Luminance difference between the color target and the unexpected onset was manipulated in the first two experiments. In Experiment 3, the unexpected onset remained on the screen continuously after its appearance (i.e., no offset in the display). In Experiment 4, two colors were presented simultaneously for discrimination. Results showed that the unexpected onset could capture attention in the color detection tasks, but the capture effect was varied with luminance manipulation (Experiment 1 and 2). The onset capture effect disappeared, however, when the onset was not followed by an offset (Experiment 3), and when two color changes were to be discriminated. Since the onset capture effect was sensitive to changes in luminance, the presence of offset, and the number of changes, we conclude that the onset capture effect observed in the IB task resulted from transient changes.