The effects of perceptual load on semantic processing under inattention. 
Inattentional blindness refers to a failure to consciously detect an irrelevant object that appears without any expectation when attention is engaged with another task.  The perceptual load theory predicts that task-irrelevant stimuli will reach awareness only when the primary task is of low load, which allows processing resources to spill over to processing task-irrelevant stimuli as well.  We studied whether perceptual load has an effect on inattentional blindness for a task-irrelevant stimulus whose meaning is or is not relevant to the attentional goals of the observer.  In the critical trial, a word appeared without any expectation in the center of a display of attended pictures.  The results showed that, under both high and low load, unexpected words belonging to the attended semantic category were detected more often than semantically unrelated words.  These results imply that task-irrelevant stimuli, whose meanings are relevant to the observer's task, enter awareness irrespective of perceptual load.