Rod and frame alignment times increase when the frame is tilted.

Abstract

The Rod and Frame test measures an individual’s subjective assessment of visual vertical and horizontal in the presence of a surrounding tilted frame. Attention has focused upon the effects of the surrounding frame upon spatial accuracy (Spatial Frame Effect). We have investigated if the tilted frame also affects the time that subjects take to make the alignment (Temporal Frame Effect). Results: 125 subjects performed a computerised Rod and Frame test to investigate the effects of a tilted frame on subjective visual vertical and horizontal. In addition the program recorded the time taken to make each alignment. For most subjects the mean Spatial Frame Effect was small (vertical 1.62, SD 0.93; horizontal 1.9, SD 1.43). The mean time taken to make alignments in the presence of a tilted frame was longer than when the frame was not tilted (vertical, +3.4s, SD 4.4; horizontal, +3.2s, SD 4.5). Differences in the times taken when the rod and frame were presented congruently and incongruently could be fully accounted for by the differences in steps needed to move the rod to its final alignment. No relationship was found between the spatial accuracy and the time to make the alignment and there was no relationship between the Spatial and Temporal Frame Effects. Conclusions: This study suggests that the Spatial, and Temporal, Frame Effects provide information about different aspects of the process of resolving conflicting visual information when making judgments on alignment. In everyday functions such as the maintenance of balance or susceptibility to motion sickness, the increased time taken may be as important as spatial accuracy.