ABSTRACT
All inhibition models that have been developed thus far (van der Ven & Smit, 1982; van der Ven, Smit, & Jansen, 1989; Smit & van der Ven, 1995), are based on the general assumption that any mental act that requires a minimum amount of mental effort actually consists of a continuous sequence of alternating periods of attention (or work) and distraction (or nonwork). In periods of attention the person is actually working at the task, whereas in periods of distraction the person is not working on the task. Distractions are unconscious, involuntary periods of nonwork. Distractions should not be confused with periods of nonwork in which subjects consciously take time out. These inhibition models have been developed to account for the reaction-time fluctuations in prolonged work tasks. In prolonged work tasks subjects are required to engage in simple, repetitive activities, such as letter cancellation, detecting differences in simple shapes, adding three digits, and so on. Performance is recorded as a series of response (or reaction) times. Subjects are instructed to work as quickly and as accurately as possible. The items should be answered in a self-paced continuous manner, in which the subject cannot afford to take intermediate rest pauses between responses. In this way one is able to study “the fluctuations which always occur in any person's continuous output of mental work, even when this is so devised as to remain of approximately constant difficulty” (Spearman, 1927, p. 320). Prolonged work tasks are used especially in concentration tests, which were already in use by the beginning of this century (see, among others, Binet, 1900).
