POSSIBLY DEPENDENT PROBABILITY SUMMATION OF REACTION-TIME

The redundant target effect is frequently observed in certain reaction time experiments. A probability summation mechanism is commonly invoked to explain the observed decrease of reaction time (RT). Here, probability summation models of RT are generalized by dropping the assumption of stochastic independence among processing times. An upper bound for the amount of statistical facilitation possible under negative dependence is derived for the bivariate case. Consequences for models of binocular summation and bisensory interaction are outlined and the main result is illustrated by a comparison of visual/auditory RT data with a simulated dependent probability summation mechanism. The impact of a base time component of reaction time in these simulations is characterized. Finally, it is shown that the detection paradigm can formally be treated under the reaction time paradigm. © 1990.