Analysis of a constraint on perception, cognition, and development: one object, one place, one time.

It has become increasingly common for theories to rely on a constraint that 1 object cannot be in more than 1 place at the same time. Analysis suggests that a 1 object-1 place-1 time constraint as literally stated is false, that a modified constraint is biased toward the visual modality, that it may not be a correct description of the physical world, is not true of how objects must appear on sensory surfaces, and does not mean that 2 simultaneous spatially separated samples must be interpreted as 2 different objects, even for vision. However, once such object numerosity or identity is determined in some other way, then a modified constraint can be used to trigger learning, such as prism adaptation. A far-removed implication is that "Where is an object?" may be a misleading question. (c) 2004 APA, all rights reserved