Abstract
Prior research has found imagined and executed actions often exhibit similar temporal characteristics, suggesting a common mechanism for both simulated and physical actions. However, discrepancies in the timing between simulated and executed actions emerge under encumberment. When wearing a heavy backpack imagined walking time increases, but actual walking times are unchanged (Decety et al., 1989). Similarly, when reaching with a weighted pencil imagined reaching times increase while actual reaching times remain unchanged (Ceretelli et al., 2000). These increases in the timing of imagined actions have been generally attributed to compensation for effort during simulation. We propose a more specific alternative explanation, perceived distance influences imagined actions.
In the present work, we manipulated perceived distance to a target and measured imagined and actual walking times to the target. Previous research has shown perceived distance is affected by effort (Proffitt et al., 2003), intention (Witt et al., 2005), and environmental context (Witt et al., in press). Perceived distance was manipulated by placing a target on a hill, thus increasing effort and through the use of a barrier and segmented cones which created an illusion of increased distance. The actual target distance remained constant.
The results showed the following: 1) Imagined walking times were higher when distances were perceived to be greater. 2) Positive correlations between imagined walking time and perceived distance were obtained. 3) Actual walking times did not change with manipulations of perceived distance.
Our results indicate that perceived distance serves as input information for imagined actions. This specific explanation can account for changes in simulated walking times under encumberment and when manipulations of perceived distance occur.