Simple Summary Good animal welfare requires minimizing suffering and promoting positive
experiences. To achieve this, we need reliable indicators of animals' psychological states. In …

Primates are noted for their varied and complex pelage and bare skin coloration but the
significance of this diverse coloration remains opaque. Using new updated information …

I examine Alfred Russel Wallace's six biological categories of coloration of animals and
plants, and review how they have been developed over the subsequent century and a half …

Sexual selection produces extravagant male traits, such as colorful ornaments, via female
mate choice. More rarely, in mating systems in which males allocate mating effort between …

Like catarrhines, some platyrrhines show exposed and reddish skin, raising the possibility
that reddish signals have evolved convergently. This variation in skin exposure and color …

Humans exhibit a suite of developmental changes in social cognition across the lifespan. To
what extent are these developmental patterns unique? We first review several social …

Primates are remarkably colourful in comparison to other mammals. In particular, several
species exhibit red–orange pelage or bright red skin, with the latter thought to signal status …

Exaggerated male traits can evolve under intra-or intersexual selection, but it remains less
clear how often both mechanisms act together on trait evolution. While the males of many …

Primate faces provide information about a range of variant and invariant traits, including
some that are relevant for mate choice. For example, faces of males may convey information …

Discriminating conspecifics from heterospecifics can help avoid costly interactions between
closely related sympatric species. The guenons, a recent primate radiation, exhibit high …