On the metric properties of visual images generated from verbal descriptions: Evidence for the robustness of the mental scanning effect

When subjects mentally scan across visual images of spatial configurations, the "mental scanning effect" is said to occur when there is a linear relationship between distances scanned and scanning times. This effect has been documented in studies where configurations were learned perceptually, and also when mental images of spatial configurations were constructed from verbal descriptions. The scanning effect is generally taken to indicate that visual images incorporate the metric structure of represented objects or configurations in an analog fashion. This article reports three experiments designed to test whether the cognitive salience of landmarks in a configuration can alter the mental scanning effect. Three manipulations of landmark salience were used, but there was no evidence of such an alteration. The scanning times towards salient and non-salient landmarks were quite similar, and the experimental manipulations had no effect On the time-distance correlation coefficients. We conclude that the structural organisation of visual images constructed from verbal descriptions is robust, since semantic variations in the descriptions did not affect the mental scanning effect. The experiments showed that high visuo-spatial imagers (as classified on the basis of their scores on the Minnesota Paper Form Board) consistently had shorter scanning times than low imagers, and that only the responses of high imagers gave the time-distance correlation coefficients characteristic of the mental scanning effect. These findings suggest that the visual images constructed by high imagers include more accurate metric information than those constructed by low imagers.