Wholes, holes, and basic features in vision.

A key issue for theories of perception is specifying the primitives used by the visual system to isolate and identify the objects in an image. Although local features are typically suggested, there is good reason to look for global, configural features as primitives too. Chen et al.'s specific proposal of topological features is both explicit and capable of capturing important global information. It may seem surprising that topology can be detected by honeybees, but Chen's results are in keeping with other findings from humans that global properties are sometimes perceived better than local ones and thus might be basic.