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The joint effects of task complexity and response probability on response latency : a test of the existence of a defensive strategy in a two-choice reaction time task Leech, Maureen I.


The main purpose of this study was to determine if subjects would employ a defensive type strategy in a two-choice reaction time task using tasks of unequal response complexity. The methodology used to investigate this problem involved examining the joint effects of two levels of task complexity and eight levels of response probability on response latency in one simple and seven choice experimental conditions. The hypothesized effects of response probability on response latency for tasks of unequal complexity are summarized as follows: (1) below a probability level of .50, response latency was expected to decrease as response probability decreased, and (2) above a .50 probability level no significant increase or decrease in response latency relative to the equal probability level was expected. The experimental task was a discrete, two-choice reaction time task, in which subjects were required to depress several response keys in a predetermined order following the onset of one of two possible stimulus lights. Two tasks of varying complexity were used: (1) a simple task involving two response keys only, and" (2) a complex task requiring the depression of five response keys in a specific order. Probability levels of 1.0, .90, .75, .60, .50, .40, .25, .10 provided eight experimental conditions under which the two tasks were performed. Sixteen male students from the University of British Columbia served as subjects. The empirical results did not provide support for the predicted hypotheses. It was found that for tasks of unequal complexity, subjects did not adopt a defensive strategy by preparing for the more difficult or less probable response. Results for both tasks illustrated a classical probability effect, i.e., an increase in probability results in a decrease in response latency, contrary to the predicted results for tasks of unequal complexity. Also, the extreme probability levels of .90 and .10 had a marked effect on the response latency for both tasks with the simple task showing greater variability than the complex task due to these probability levels. Data from this experiment tended to support the premise that response probability is a decreasing function of task complexity, i.e., the more complex the task the less effect response probability has on the resulting response latency.

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