Chronometric evidence for two types of attention

Parallel processing in the human brain is subject to severe attentional limits, but it is unclear whether such limits arise from a single attentional process or multiple distinct attentional processes. We provide new evidence that two candidates, input attention and central attention, operate at different temporal stages of processing. This conclusion is supported by chronometric analyses showing that the same reference stage (letter identification) operates after the stage at which input attention operates, but prior to the stage at which central attention operates. The finding that attention operates at different temporal loci provides new support for the existence of distinct attentional processes.