Memory for the final location of a moving target is often displaced in the direction of target motion, and this has been referred to as representational momentum. Characteristics of the target (e.g., velocity, size, direction, and identity), display (e.g., target format, retention interval, and response method), context (landmarks, expectations, and attribution of motion source), and observer (e.g., allocation of attention, eye movements, and psychopathology) that influence the direction and magnitude of displacement are reviewed. Specific conclusions regarding numerous variables that influence displacement (e.g., presence of landmarks or surrounding context), as well as broad-based conclusions regarding displacement in general (e.g., displacement does not reflect objective physical principles, may reflect aspects of naive physics, does not solely reflect eye movements, may involve some modular processing, and reflects high-level processes) are drawn. A possible computational theory of displacement is suggested in which displacement (1) helps bridge the gap between perception and action and (2) plays a critical part in localizing stimuli in the environment.
An observer's memory for the final position of a previously viewed moving target is often displaced forward in the direction of target motion. This displacement has been suggested to reflect the implied momentum of the target and has been referred to as representational momentum (Freyd & Finke, 1984; for a sampling of recent research, see Thornton & Hubbard, 2002). Momentum is one of several physical principles that has been suggested to influence memory for the position of a target, and evidence previously interpreted as suggesting that momentum and other physical principles influence spatial representation, as well as evidence regarding other variables that influence this displacement, will be reviewed. Although it may seem counterintuitive that such a distortion or bias in mental representation could be adaptive, such displacement may play an important role in the spatial localization of stimuli by helping to bridge the gap between perception and action. Creating such a bridge could help observers localize and optimally respond to stimuli, and so such displacement in the mental representation of the final position of a target could be a critical part of a larger computational theory of perception.
Overview of Displacement
In early studies of displacement, researchers used the term representational momentum to refer to any mislocalization of the remembered final position of a moving target in the direction of target motion. However, there are a number of potential issues with this term. First, and as will be discussed in more detail below, mislocalization of the final position of a moving target in the direction of motion is influenced by variables other than the implied momentum of the target. The term representational momentum does not accurately describe a combination of momentum and nonmomentum variables, nor does it distinguish between effects of implied momentum and effects of other variables. second, the term representational momentum has been used to refer to displacement along any dimension of change, even when change along that dimension might not be associated with physical momentum (e.g., auditory frequency, Freyd, Kelly, & DeKay, 1990; brightness, Brehaut & Tipper, 1996; facial expression, Thornton, 1998). Third, the term representational momentum has been used to describe a forward mislocalization of the final position of a moving target and also as an explanatory mechanism for that forward mislocalization, and this has resulted in a blurring of data and theory. Fourth, mislocalization of the final position of a moving target can occur in directions other than the direction of target motion, and mislocalization in these other directions would not reflect effects of momentum.
Given the issues associated with the term representational momentum, Hubbard (1995c) has suggested that the broader term displacement should be used to refer to general mislocalizations in memory for the final position of a target, and the more specific term representational momentum should be used only to refer to that component of displacement that is attributed to the implied momentum of the target. …