Redundancy gains in simple responses and go/no-go tasks

In divided-attention tasks with two classes of target stimuli, participants typically respond more quickly if both targets are presented simultaneously, as compared with single-target presentation (redundant-signals effect). Different explanations exist for this effect, including serial, parallel, and coactivation models of information processing. In two experiments, we investigated redundancy gains in simple and go/no-go responses to auditory-visual stimuli presented with an onset asynchrony. In Experiment 1, go/no-go discrimination was performed for near-threshold and suprathreshold stimuli. Response times in both the simple and go/no-go responses were well explained by a common coactivation model assuming linear superposition of modality-specific activation. In Experiment 2, the go/no-go task was made more difficult. Participants had to respond to high-frequency tones or right-tilted Gabor patches and to withhold their response for low tones and left-tilted Gabors. Redundancy gains were consistent with coactivation models; however, channel-specific buildup of evidence seems to occur at different speeds in the two tasks. Response times of 1 participant support a serial self-terminating model of modality-specific information processing. Supplemental materials for this article may be downloaded from http://app.psychonomic-journals.org/content/supplemental.