Abstract
The cornerstone of the face processing research agenda is an understanding of the processes underlying the identification of faces. We examined whether local or global information subtends face identification. To this end, we introduced a new methodology (iHybrid, see supplementary Figure 1 for a sketch of the methodology) that combines two identities in an on-line, fixation-dependent paradigm, which simultaneously provides local, foveated information from one face (supplementary Figure 1, the left eye of Brad Pitt, across spatial frequencies) and global, complementary information from a second face (the complementary facial information from William Macy) and then update the display at the location of the next fixation (See example movie for an illustration of the dynamics of fixations over one trial; the dot represents the fixation location: http://www.psy.gla.ac.uk/∼roberto/iHybrid_example.mov). iHybrids revealed the existence of two distinct, equally frequent and equally effective information sampling strategies for face identification. The local strategy involves local fixations on the eyes and the mouth; the global strategy relies on central fixations of the face. All observers used both strategies, often to recover the very same identity in different trials of the same experiment. We provide an illustration of the local and global information use in supplementary Figure 2. We conclude that the face system flexibly uses local or global stimulus information to identify faces and examine the implications of our findings for face identification.
The Economic and Social Research Council and Medical Research Council (ESRC/RES-060-25-0010).