Social experience drives the development of holistic face processing in paper wasps.

Most recognition is based on identifying features, but specialization for face recognition in some taxa relies on a different mechanism, termed 'holistic processing' where facial features are bound together into a gestalt which is more than the sum of its parts. Although previous work suggests that extensive experience may be required for the development of holistic processing, we lack experiments that test how age and experience interact to influence holistic processing. Here, we test how age and experience influence the development of holistic face processing in Polistes fuscatus paper wasps. Previous work has shown that P. fuscatus use facial patterns to individually identify conspecifics and wasps use holistic processing to discriminate between conspecific faces. We tested face processing in three groups of P. fuscatus: young (1-week-old), older, experienced (2-weeks-old, normal experience), and older, inexperienced (2-weeks-old, 1 week normal social experience and 1 week social isolation). Older, experienced wasps used holistic processing to discriminate between conspecific faces. In contrast, older inexperienced wasps used featural rather than holistic mechanisms to discriminate between faces. Young wasps show some evidence of holistic face processing, but this ability was less refined than older, experienced wasps. Notably, wasps only required 2 weeks of normal experience to develop holistic processing, while previous work suggests that humans may require years of experience. Overall, P. fuscatus wasps rapidly develop holistic processing for conspecific faces. Experience rather than age facilitates the transition between featural and holistic face processing mechanisms.