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The prior entry hypothesis of attention holds that attended stimuli are perceived earlier than unattended stimuli. Whereas this speeding of perceptual processing has been repeatedly demonstrated for spatial attention, it has not been reported within the temporal domain. To fill this gap, we tested whether temporal attention accelerates auditory perceptual processing by employing event-related potentials as on-line indicators of perceptual processing. In a modified oddball paradigm, we presented a single tone in each trial, either a frequent standard tone or an infrequent deviant or target tone. Temporal attention to tones was manipulated via constant foreperiods. We observed that the latency of the N2, an event-related potential reflecting perceptual processing, is shortened by temporal attention. This result provides first evidence for the idea that temporal attention accelerates perceptual processing as suggested by the prior entry hypothesis.

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In two experiments, each including a simple reaction time (RT) task, a localization task, and a passive oddball paradigm, the physical similarity between two dichotically presented auditory stimuli was manipulated.In both experiments, a redundant signals effect (RSE), high localization performance, and a reliable mismatch negativity (MMN) was observed for largely differing stimuli, suggesting that these are coded separately in auditory memory. In contrast, no RSE and a localization rate close to chance level (experiment 1) or at chance (experiment 2) were observed for stimuli differing to a lesser degree. Crucially, for such stimuli a small (experiment 1) or no (experiment 2) MMN were observed. These MMN results indicate that such stimuli tend to fuse into a single percept and that this fusion occurs rather early within information processing.

Previous reaction time studies have demonstrated coactivation processes within the visual modality for redundant stimuli that differ in two dimensions (e.g., shape and color). The present study provides novel results of analogous processes within the auditory modality. A redundant-target effect (RTE) was obtained in a Go/NoGo experiment using tones that differed in location and/or frequency. Participants were asked to respond to a specific tone location (e.g., left) and/or tone frequency (e.g., 200 Hz) of auditory stimuli. For redundant targets (e.g., a 200 Hz tone presented to the left), an RTE was observed which was too large to be explained by mere statistical facilitation. Therefore, responses to redundant targets were triggered by a combined activation of the target dimensions. The results are consistent with the modular hybrid account of Mordkoff and Yantis (1993).