Seibold, V. C. , Bausenhart, K. M. & Rolke, B.
Eberhard Karls Unversität Tübingen, Tübingen, Germany
Over the past ten years, a variety of studies have shown that temporally expecting a stimulus facilitates perceptual processing. To investigate the possible mechanisms underlying this perceptual benefit, we conducted two studies. In the first study, we used speed-accuracy-tradeoff (SAT) functions to assess whether temporal expectancy affects the dynamics of perceptual processing. Specifically, we used a spatial discrimination task in which participants had to judge whether the upper line of a cross was longer or shorter then the other ones. The time available for target processing was varied by presenting a response signal with a variable delay after target onset, and temporal expectancy for targets was manipulated via constant foreperiods. The obtained SAT functions suggest that temporal expectancy acts on the onset of perceptual processes. In the second study, we aimed to find possible neuronal markers for this onset effect by means of sensory event-related potentials (ERPs). Specifically, we used an auditory oddball task in which participants had to detect infrequent target tones intermixed in frequent standard and infrequent deviant tones. Temporal expectancy was again manipulated via constant foreperiods. We observed that the latencies of sensory ERPs, i.e. the N1 and the N2 difference wave, were shortened in conditions of high temporal expectancy. Taken together, the two studies provide first evidence that temporal expectancy leads to a perceptual benefit by shortening the onset of perceptual processes.