The Effect of Visual Movement Information on Texture Discrimination Performance and Movement Control in Active Touch

In daily life, people assess different properties of objects such as texture or hardness by active touch. Vision of hand movements can improve tactual discrimination performance, even without giving visual cues to stimulus properties (Suzuishi & Hidaka, 2022). Here, we studied how visual information on finger movements affects texture perception by active touch. In a previous experiment without visual information, we found that participants adapt their exploratory movement in texture discrimination to the direction of finger movement. In the present study, we investigated whether viewing the finger movements affects the patterns of motor control and discrimination performance. We used oriented ridge-grooove textures (groove width 11.3 to 19.3 mm, 0.5 mm ridge width, 0.5 mm depth). There were 9 stimuli in total, 1 standard, 4 lower and 4 higher spatial frequencies. Participants were asked to choose a stimulus with higher spatial frequency in a two-interval forced choice task (combined with method of constant stimuli). Participants' finger was orthogonal to the texture orientation while they explored in the anteroposterior or lateral direction relative to the body. Finger movement was represented by a cursor. The visual display did not provide any cue on spatial frequency of the surface but observers were able to see their finger velocity and effects of their applied force (through the height of the cursor). Actually, results with visual information on movement were similar to that in the previous study without visual information with respect to discrimination performance (JNDs), movement forces and movement velocity. Also, similar as in the previous study, participants applied more force when moving in the anteroposterior as compared to lateral direction. This force variation can be understood as improving performance in the anterioposterior condition, while we did not find evidence that visual guidance strongly contributes to performance or control in this task.