Abstract
Beats are among the basic units of perceptual experience. Produced by regular, intermittent stimulation, beats are most commonly associated with audition, but a similar experience can be produced by stimulation in other sensory modalities as well. In this study, I conducted two experiments to investigate beat perception in visual and vibrotactile modalities. In both experiments, subjects attempted to discriminate between pulse sequences delivered in the 3-6 Hz range, categorizing pulse sequences as either “fast” or “slow”. In the first experiment, visual, vibrotactile, and bimodal pulses were used. In the second experiment, I focused on the two unimodal conditions. On the majority of trials presented in each experiment, inter-pulse intervals (IPIs) were stochastic, perturbed by random samples from zero-mean Gaussian distributions with different variances. These perturbations produced directional changes in the IPIs, which either increased or decreased the likelihood of confusing “fast” and “slow” pulse rates. This paradigm made it possible to gauge how subjects’ judgments were influenced by successive IPIs. Logistic regression revealed strong primacy effects: in both experiments, subjects’ decisions were disproportionately influenced by each trial’s initial IPIs. Error analysis suggested consistent reliance on statistically optimal decision criteria, adjusted in real time depending on the amount of external noise present in successive IPIs. Finally, temporal information delivered by vibrotactile signals proved just as robust as that conveyed by visual signals, confirming vibrotactile stimulation’s potential for timely communication.