Channel interaction and the redundant-targets effect in bimodal divided attention.

In bimodal divided attention tasks, people respond faster to simultaneously presented redundant targets than to single targets. Previous research supports "coactivation" models, in which redundant targets both activate the response. This study sought to determine whether redundant targets activate the response independently, with each target producing its own activation, or interactively, with activation produced by redundant targets being a joint function of both their identities. Experiment 1 used auditory targets varying in pitch and visual targets varying in location. Responses to redundant targets were faster when both were high or low than when they were incongruent. Experiment 2 varied joint probability of redundant pairs, and responses were faster to common pairs than rare ones. The results indicate that responses to redundant targets are a joint function of both identities, not a concatenation of independent activations.