Searching for faces in scrambled scenes

While much is known about how faces are recognized, little is known about how a face is first detected. Five face-detection experiments investigated how faces are localized and detected among either scrambled natural backgrounds or inverted faces. The first two experiments revealed that faces pop out among the former but must be searched for serially among the latter. Two subsequent experiments investigated what properties of a face allow for this pop-out. Colour removal or reversal, blurring, and inversion all had small effects on the visual search slope. The only transformation that reduced the parallel nature of face detection was luminance reversal. These results are considered in the light of models of face processing and systems for automatic face detection