Attentional capture by unique temporal change

Abstract

The time course of attentional capture was measured in the preview search paradigm (Yantis & Joinides, 1984). Participants were first presented a circular preview display of figure eights. After one second two to four line segments of each figure eight were deleted to reveal a search display of letters, with two letters arbitrarily designated as targets. The participant's task was to press one of two keys as rapidly as possible to report target identity. Attentional capture was indexed by the relative ratio of RT slopes, taken over the display size, for targets that appear in unchanged versus unique display item locations. This is based on the assumption that when a unique item draws attention to itself, it will slow search if it happens to be one of the distractor letters. The current study points to a temporal factor, over and above the importance of new objects and relative signal speed, which is critical for attentional capture. Attention is captured by temporally unique events. The results of three experiments show that feature changes capture attention as effectively as new objects provided they occur during a period in which the display is static. Conversely, these same feature changes do not capture attention when they occur simultaneously with other display changes, such as the sudden onset of all items or the deletion of some line segments in all items. Importantly, the results show that this unique event hypothesis applies to changes in color (Experiment 1), in motion (Experiment 2) and even to the sudden appearance of new objects (Experiment 3). These findings highlight the importance of considering both space and time in studies of attentional capture.