Dr Maria Santacà is a behavioral biologist who specializes in the study of animal cognition and perception. Her research at the Department of Behavioral & Cognitive Biology of the University of Vienna explores how visual illusions can reveal the evolutionary roots of perception, asking whether similarities and differences across species reflect shared ancestry and neural complexity, or unique adaptations to ecological and social environments. In a newly published Frontiers in Psychology article, she uses a trick of vision where identical circles appear larger or smaller, depending on the context, to investigate differences in perception. She studied this two very different species: guppies and ring doves. In the following guest editorial, she describes how not only how fish and birds perceive their worlds, but also how ecological pressures shape the evolution of perception.