Abstract
When psychologists began to use intelligence tests, they also used simple, overlearned tasks to determine the pattern of individual reaction times (RT). Measures of RT variation were proposed as possible indicators of intelligence. However, a fundamental question has remained partly unanswered: Is there an existing theory that explains individual RT variation? In this paper, a theory is proposed for the response times obtained in the Attention Concentration Test. The test consists of two different conditions: a fixed condition and a random condition. For each of these two conditions a different RT model was developed both based on the basic assumption that the individual response times have an approximately shifted exponential distribution. Empirical data was obtained from two different samples (N = 362, N = 334) of Finnish students. The method used to check the validity of each model involved computing the intercept and slope of the linear regression of the standard deviation from the stationary response times on the mean corrected for shift. In this regression analysis, the standard deviation is the dependent variable and the mean corrected for shift the independent variable. The shift parameter was estimated by using the smallest reaction time. The observed intercept and slope were compared with the predicted intercept and slope according to the proposed models. The model for the fixed condition of the test did not hold. The model for the random condition,however, did. The findings were interpreted according to the arrangement of the targets as they occurred in each bar.
