Journal of Vision, 5. 2005. [VSS 2005; Sarasota, FL, USA.]

Inattentional Blindness (IB) is the failure to see the presence of an item when it is not attended. Previous studies (e.g., Neisser & Becklen, 1975; Mack & Rock, 1998) relied on having the observer attend to one part of a visual display and then presenting an unexpected--and thus unattended--part that the observer is subsequently queried about. But the need for an unexpected stimulus creates problems. For example, the test stimulus is unexpected only the first time it appears, making extensive exploration of IB difficult. And at the theoretical level, it leaves open the possibility that IB is not really a failure to see the stimulus, but rather is a failure to remember it long enough to be queried about it (Wolfe, 1999).

To address these concerns, a 'locked onset' technique was developed in which a test stimulus appeared the moment the observer attended to some other part of the display. In each trial, observers viewed a set of items that briefly appeared and then made a sudden change; a test stimulus then appeared in the center of this display on half the trials. Observers were asked to report whether the monitored items did or did not change uniformly, and whether the test stimulus appeared. The onset of this stimulus was locked to the moment the monitored changes occurred, so that attention could not be easily given to it. Detection rates therefore indicated whether observers are blind to an unattended stimulus, even when it is expected.

Results showed blindness rates comparable to those reported in previous studies, even when there were 192 trials per observer, and test stimuli were displayed for 400 ms. Since observers were prepared to respond to the test stimulus, this shows that IB is due to a failure to see rather than a failure to remember. These results also indicate that the locked onset technique may form a simple and practical basis for the exploration of IB.

Support provided by the Natural Sciences and Engineering Research Council of Canada and Nissan Motor Co., Ltd.