Cognitive psychology

Ecology

Neuroscience

Biology

Identification (biology)

Face (sociological concept)

Computer security

Astrophysics

Computer science

Botany

Recall

Variation (astronomy)

Physics

Psychology

Need to know

Pattern recognition (psychology)

Sociology

Perception

Facial recognition system

Social science

Proceedings of the Royal Society B Biological Sciences

Over our species history, humans have typically lived in small groups of under a hundred individuals. However, our face recognition abilities appear to equip us to recognize very many individuals, perhaps thousands. Modern society provides access to huge numbers of faces, but no one has established how many faces people actually know. Here, we describe a method for estimating this number. By combining separate measures of recall and recognition, we show that people know about 5000 faces on average and that individual differences are large. Our findings offer a possible explanation for large variation in identification performance. They also provide constraints on understanding the qualitative differences between perception of familiar and unfamiliar faces-a distinction that underlies all current theories of face recognition.

How many faces do people know?