Mere presence of co-eater automatically shifts foraging tactics toward “fast and easy” food in humans

Competition for food resources is widespread in nature. The
foraging behavior of social animals should thus be adapted to
potential food competition. We hypothesized that in the presence of
co-foragers, animals would shift their tactics to forage more frequently
for smaller food. Because smaller foods are more abundant in nature and
allow faster consumption, such tactics should allow animals to consume
food more securely against scrounging. We tested whether humans would
exhibit such a shift. To prevent subjects from having rivalry, they were
instructed to engage in a “taste test” in a laboratory, alone or
in pairs. Even though the other subject was merely present and there was
no real competition for food, subjects in pairs immediately exhibited a
systematic behavioral shift to reaching for smaller food amounts more
frequently, which was clearly distinct from their reaching patterns both
when eating alone and when simply weighing the same food without eating
any. These patterns suggest that behavioral shifts in the presence of
others may be built-in tactics in gregarious animals to adapt to potential
food competition in social foraging.