Independent effects of temporal expectation and stimulus intensity in audition.

Temporal orienting--that is, selective attention to instants in time--has been shown to modulate performance in terms of faster responses in a variety of paradigms. Electrophysiological recordings have shown that temporal orienting modulates neural processing at early, probably perceptual, and late, probably decision- or response-related, stages. Recently, it was shown that the effect of temporal orienting on early auditory brain potentials is independent of the effect of the physical sound feature intensity. This indicates that temporal orienting might not affect stimulus processing by increasing the sensory gain of attended stimuli. In the present study, we investigated whether the independence of temporal-orienting and sound-intensity effects could be replicated behaviorally. Sequences were presented that were either rhythmic, most likely creating temporal expectations, or arrhythmic, presumably not creating such expectations. As hypothesized, the main effects of temporal expectation and sound intensity on reaction times were independent (Experiment 1). The exact pattern of results was replicated with a slightly altered paradigm (Experiment 2) and with a different kind of task (Experiment 3). In sum, these results corroborate the notion that the effect of temporal orienting might not rely on the same processes as the effect of sound intensity does.