Abstract
When actively attending to targets in a display, observers often fail to notice an additional, unexpected stimulus (Mack & Rock, 1998). This “inattentional blindness” occurs for salient objects visible for extended periods of time (Most et al., 2001). Here we show that inattentional blindness can occur even when the unexpected object is the only item visible in the display. On each trial, observers tracked two white circles among six black circles that moved randomly and independently around the display. Each trial contained a 1200 ms blank interval in which all items became invisible by fading out, but the circles' positions continued to be updated according to the same rules as when they were visible. Observers were required to extrapolate the target circles' trajectories during the blank interval to enable recovery of the objects when they reappeared. Upon reappearing (by fading in), all circles were identical, and observers indicated which items they had been tracking before the blank. This task was difficult but possible: with practice, 95% of the observers were able to select at least one of the target items accurately. On a critical trial, an additional, unexpected black circle faded in at fixation at the beginning of the blank interval and remained until the original items reappeared, at which point the unexpected circle faded out. Even though the unexpected circle was the only object in the display during this 1200 ms interval, 25% of the observers failed to notice it. This rate is consistent with previous inattentional blindness research (Mack & Rock, 1998), but is especially striking given that no other objects were visible.