The speed of focal attention in early vision

Previous investigations reported the speed of focal attention to be at least as fast as 33.3 msec per item (for 1-4 items displayed serially). In this study, the speed of presentation was increased to 16.7 msec per item (RS-170 standard field rates) using an advanced digital real-time image video system. Four observers participated in this study. Performance was based on the percentage of correct responses. Using stimulus onset asynchronies (SOAs) of 16.7, 33.3, and 50 msec, the authors found that performance decreased with faster SOAs. All subjects performed well above the theoretical chance level, even for four objects displayed in a sequence. Therefore, the authors conclude that the speed of focal attention is at least 12 times as fast as the saccadic scanning rate of the human eye