Identification of vibrotactile patterns: building blocks for tactons

Vibrotactile stimuli vary along a number of dimensions including frequency, amplitude, waveform and temporal profile all of which can be varied to create tactons. The objective of the present experiment was to measure tactile pattern recognition using eight vibrotactile stimuli that varied with respect to frequency, amplitude and pulse duration. An absolute identification paradigm was used in which each stimulus was presented eight times to the index finger or forearm and participants had to identify the visual image associated with the tacton. The results from the experiment indicated that in the absence of spatial cues, tactons were relatively difficult for participants to identify, with an overall mean recognition rate of 57% correct and an IT of 1.72 bits. However, there were significant differences in the identification rates among the tactons, with mean scores ranging from 30% to 83 % correct. Tactons created using higher frequencies and amplitudes were easier to identify than those with lower frequencies and amplitudes. Surprisingly, there was no difference between the finger and the forearm in tacton identification. The dimension that appeared to be most difficult to encode was amplitude, as reflected in the patterns of misidentification in the confusion matrices. These findings indicate that the specific dimensions and stimulus ranges selected to create tactons can profoundly affect the ability to identify tactile patterns and that differences in spatial and temporal acuity across the skin are not predictive of these abilities.