When categories collide: accumulation of information about multiple categories in rapid scene perception.

Experiments have shown that people can rapidly determine if categories such as "animal" or "beach" are present in scenes that are presented for only a few milliseconds. Typically, observers in these experiments report on one prespecified category. For the first time, we show that observers can rapidly extract information about multiple categories. Moreover, we demonstrate task-dependent interactions between accumulating information about different categories in a scene. This interaction can be constructive or destructive, depending on whether the presence of one category can be taken as evidence for or against the presence of the other.