Taking up new approaches and calls for experimental test validation, in the present study we propose and validate a process model of sustained attention tests. Four sub-components were postulated: the perception of an item, a simple mental operation to solve the item, a motor reaction, and the shift to the next item. In two studies, several cognitive tasks and modified versions of the d2-R test of sustained attention were applied in order to determine performance in the proposed sub-components. Their contribution for the prediction of performance in sustained attention tests and tests of higher cognitive abilities was assessed. The sub-components of the process model explained a large amount of variance in sustained attention tests, namely 55-74%. More specifically, perceptual and mental operation speed were the strongest predictors, while there was a trend towards a small influence of motor speed on test performance. The measures of item shifting showed low reliabilities and did not predict test scores. In terms of discriminant validity, results of Study 1 indicated that the postulated sub-components were insufficient to explain a large amount of variance in working memory span tasks, in Study 2 the same was demonstrated for reasoning tasks. Altogether, the present study is the first to disentangle sub-components in sustained attention tests and to determine their role for test performance.
Keywords: concentration; experimental test validation; process model; processing speed; reasoning; sustained attention; working memory capacity.