Exploring melodic variance in rhythmic haptic stimulus design.

Haptic icons are brief, meaningful tactile or force stimuli designed to support the communication of information through the often-underutilized haptic modality. Challenges to producing large, reusable sets of haptic icons include technological constraints and the need for broadly-applicable and validated design heuristics to guide the process. The largest set of haptic stimuli to date was produced through systematic use of heuristics for monotone rhythms . We hypothesized that further extending signal expressivity would continue to enhance icon learnability. Here, we introduce melody into the design of rhythmic stimuli as a means of increasing expressiveness while retaining the principle of systematic design, as guided by music theory. Haptic melodies are evaluated for their perceptual distinctiveness; experimental results from grouping tasks indicate that rhythm dominates user categorization of melodies, with frequency and amplitude potentially left available as new dimensions for the designer to control within-group variation.