Data from: How many faces do people know?

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.