Representations of microgeometric tactile information during object recognition.

Object recognition through tactile perception involves two elements: the shape of the object (macrogeometric properties) and the material of the object (microgeometric properties). Here we sought to determine the characteristics of microgeometric tactile representations regarding object recognition through tactile perception. Participants were directed to recognize objects with different surface materials using either tactile information or visual information. With a quantitative analysis of the cognitive process regarding object recognition, Experiment 1 confirmed the same eight concepts (composed of rules defining distinct cognitive processes) commonly generated in both tactile and visual perceptions to accomplish the task, although an additional concept was generated during the visual task. Experiment 2 focused only on tactile perception. Three tactile objects with different surface materials (plastic, cloth and sandpaper) were used for the object recognition task. The participants answered a questionnaire regarding the process leading to their answers (which was designed based on the results obtained in Experiment 1) and to provide ratings on the vividness, familiarity and affective valence. We used these experimental data to investigate whether changes in material attributes (tactile information) change the characteristics of tactile representation. The observation showed that differences in tactile information resulted in differences in cognitive processes, vividness, familiarity and emotionality. These two experiments collectively indicated that microgeometric tactile information contributes to object recognition by recruiting various cognitive processes including episodic memory and emotion, similar to the case of object recognition by visual information.