Social competition stimulates cognitive performance in a sex-specific manner

Social interactions are thought to be a critical driver in the evolution
of cognitive ability. Cooperative interactions, such as pair bonding,
rather than competitive interactions have been largely implicated in the
evolution of increased cognition. This is despite competition
traditionally being a very strong driver of trait evolution. Males of many
species track changes in their social environment and alter their
reproductive strategies in response to anticipated levels of competition.
We predict this to be cognitively challenging. Using a Drosophila
melanogaster model we are able to distinguish between the effects of a
competitive environment versus generic social contact by exposing flies to
same-sex same-species competition vs different species partners, shown to
pose non-competitive contacts. Males increase olfactory learning/memory
and visual memory after exposure to conspecific males only, a pattern
echoed by increased expression of synaptic genes and an increased need for
sleep. For females, largely not affected by mating competition, the
opposite pattern was seen. The results indicate that specific social
contacts dependent on sex, not simply generic social stimulation, may be
an important evolutionary driver for cognitive ability in fruit flies.