Vibrotactile Spatiotemporal Pattern Recognition in Two-Dimensional Space Around Hand

This study investigated vibrotactile spatiotemporal pattern recognition in the two-dimensional space around a hand. The participants placed their hands on the medium, and identified the recognized pattern presented in the medium. There were 64 rotational patterns, presented with sequential impulse vibrations. We investigated how well humans recognized the patterns presented around their hand, and identified the pattern factors (e.g., rotational direction) that affected recognition accuracy. The probability of obtaining correct answers was 48.9 %. It was observed that the start and end points, rotational direction, and the number of vibrations affected recognition accuracy. It was also found that patterns starting or ending on the ulnar side (
$0^{\circ }$
) of the hand were difficult to recognize, whereas those starting or ending on the distal (
$90^{\circ }$
) or proximal side (
$270^{\circ }$
) of the hand were easily recognizable. Furthermore, we found a type of the oblique effect. Patterns starting or ending in the oblique direction were more difficult to recognize than those in the cardinal direction. We also found that the clockwise rotational pattern was slightly easier to recognize than the counterclockwise rotational pattern. Finally, the underestimation of the judgment of tactile numerosity explains how the number of vibrations in the patterns affected the recognition accuracy. This result can be used as a baseline when the recognition of spatiotemporal patterns outside the body under other conditions is examined in future studies.