My study provides support for a causal relationship between group size and performance in different cognitive tests, and has shown that the link between group size and cognition is not as straightforward as previously reported.

My results did not strongly support the positive correlation between social complexity (typically represented by group size) and cognition predicted by the Social Intelligence Hypothesis. This suggests that different cognitive traits are driven by different, rather than general, genetic and neurobiological processes.

As social interactions per individual were greater in small groups than in large groups, the traditional assumption of higher social complexity with increasing group size may not always hold true. My alternative predictions associated group size differences in performance with differences in rest disturbances, vigilance and competition, but my findings were not explained by these predictions either.

I, thus, propose that the differences in performance between group sizes may be related to differences in personality, which may have led to differences in cognitive styles. Since very little is known of the links between an individual’s cognition, sociality and personality, future studies investigating the causes of intraspecific cognitive variation should assess both.