Capacity limits in face detection

Face detection is a prerequisite for further face processing, such as extracting identity or semantic information. Those later processes appear to be subject to strict capacity limits, but the location of the bottleneck is unclear. In particular, it is not known whether the bottleneck occurs before or after face detection. Here we present a novel test of capacity limits in face detection. Across four behavioural experiments, we assessed detection of multiple faces via observers' ability to differentiate between two types of display. Fixed displays comprised items of the same type (all faces or all non-faces). Mixed displays combined faces and non-faces. Critically, a ‘ xed’ response requires all items to be processed. We found that additional faces could be detected with no cost to ef ciency, and that this capacity-free performance was contingent on visual context. The observed pattern was not speci c to faces, but detection was more ef cient for faces overall. Our ndings suggest that strict capacity limits in face perception occur after the detection step.