Abstract

This study was designed to investigate the nature of representational images on mental rotation. Shepard and Metzler (1988) estimated rates of mental rotations which were much slower in the two-stimuli task than in the one-stimulus task. Differences in estimated rate of mental rotation between two tasks could be resulted from the following two components. The first one is the nature of experimental task which may induce some individuals to rotate the image of stimulus externally presented one piece at a time in the two-stimuli task, and which may induce some individuals to rotate the image of stimulus already learned as a whole in the one-stimulus task. Therefore, not the one-stimulus task but the two-stimuli task would entail still longer time to complete a mental rotation. The second one is the nature of interstimulus intervals (ISIS) which were allowed to represent standard stimulus in the one-stimulus task better than in the two-stimuli task. Because a stimulus was to be compared with an image of stimulus that was previously learned, the images would be rotate much faster in the one-stimuli task than in the two-stimulus task. In this study, the type of stimulus task was varied into the fixed-standard stimulus task and the variable-standard stimulus task. The ISIS in the study were varied into 100 msec, 500 msec, and 1000 msec. The results sheowed that there was no difference in the estimated rate of rotation between the two tasks. However, the longer ISIS were, the faster estimated mental rotation rate was. It suggested that mental rotation accomplished faster as time for representation of standard stimulus increased.