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Identifying three-dimensional signals (e.g. faces) can be challenging because the signals appear different when seen from different viewpoints. One simple solution is to always view signals from a particular viewpoint. A more flexible but also more cognitively challenging solution is viewpoint-independent recognition, where receivers can identify signals from multiple viewing angles. Here, we use same/different concept learning to test viewpoint-independent recognition for conspecific and heterospecific faces in two species ofPolistespaper wasps that have three-dimensional visual signals.P. fuscatususe conspecific facial patterns for individual recognition, whileP. dominulause conspecific facial patterns as a signal of fighting ability. Previous work has shown thatP. fuscatusare able to identify novel viewpoints of conspecific faces through extrapolation. Here, we show thatP. fuscatusandP. dominuladiffer in their capacity for viewpoint-independent recognition.P. fuscatusexhibit viewpoint-independent recognition for bothP. fuscatusandP. dominulafaces. In contrast,P. dominulado not have viewpoint-independent recognition for conspecific or heterospecific faces. These results suggest that viewpoint-independent recognition through extrapolation may be an adaptive strategy to facilitate individual face recognition across a wide range of taxa. 

ABSTRACT Visual recognition of three-dimensional signals, such as faces, is challenging because the signals appear different from different viewpoints. A flexible but cognitively challenging solution is viewpoint-independent recognition, where receivers identify signals from novel viewing angles. Here, we used same/different concept learning to test viewpoint-independent face recognition in Polistes fuscatus, a wasp that uses facial patterns to individually identify conspecifics. We found that wasps use extrapolation to identify novel views of conspecific faces. For example, wasps identify a pair of pictures of the same wasp as the ‘same’, even if the pictures are taken from different views (e.g. one face 0 deg rotation, one face 60 deg rotation). This result is notable because it provides the first evidence of view-invariant recognition via extrapolation in an invertebrate. The results suggest that viewpoint-independent recognition via extrapolation may be a widespread strategy to facilitate individual face recognition.