We argue four points. First, perception always relies on environmental constraints, not only in special cases. Second, constraints are taken advantage of by detecting information granted by the constraints rather than by internalizing them. Third, apparent motion phenomena reveal reliance on constraints that are irrelevant in everyday perception. Fourth, constraints are selected through individual learning as well as evolution. The “perceptual-concept-of-velocity” phenomenon is featured as a relevant case. [Hecht; Kubovy & Epstein; Shepard].

Stoffregen & Bardy's proposal that perceptual systems can use information defined across two or more sensory domains is valuable and urgent in its own right. However, their claim of exclusive validity for global-array information is superfluous and perpetuated for incorrect reasons. The seeming ambiguities of individual arrays emanate from failures to consider relevant ecological constraints and higher-order variables.