Further tests of the interactive race model of divided attention: The effects of negative bias and varying stimulus - Onset asynchronies

In Go/No-Go detection tasks, responses to redundant targets are typically faster than responses to either of these targets alone. One explanation of this redundant-targets effect is from race models, which assume statistical facilitation due to the activation of more than one processing channel under the redundant-targets condition. J. O. Miller (1982, 1986) has derived an upper boundary for the amount of facilitation these models can predict and has found this boundary to be consistently violated in bimodal divided-attention tasks and in letter-detection tasks. Thus, until recently race models were thought to be unable to predict the amount of facilitation commonly observed. Mordkoff and Yantis (1991) have challenged this conclusion and showed that no facilitation beyond the predictions of race models is observed if certain types of contingency within the experimental design are removed. The present study tries to replicate this basic finding and to generalize it to conditions with (a) non-simultaneous signal presentation, and (b) negative interstimulus contingency benefit. Several important predictions of Mordkoff and Yantis' interactive race model were found to hold, but for nonsimultaneous signals presentations consistent violations of Miller's upper bound were found under certain conditions. The implications of the present results for models of divided attention are discussed.