Behavioral Evidence for Two Modes of Attention

Attention modulates sensory gain to select and optimize the processing of behaviorally relevant events. It has been hypothesized that attention can operate in either a rhythmic or continuous mode, depending on the nature of sensory stimulation. Despite this conceptual framework, direct behavioral evidence has been scarce. Our study explores when attention operates in a rhythmic mode through a series of nine interrelated behavioral experiments with varying stream lengths, stimulus types, attended features, and tasks. The rhythmic mode optimally operates at approximately 1.5 Hz and is prevalent in perceptual tasks involving long (> 7 s) auditory streams. Our results are supported by a model of coupled oscillators, illustrating that variations in the system’s noise level can induce shifts between continuous and rhythmic modes. Finally, the rhythmic mode is absent in syllable categorization tasks. Overall, this study provides empirical evidence for two modes of attention and defines their conditions of operation.