THE INTERMITTENCY OF CONTROL MOVEMENTS AND THE PSYCHOLOGICAL REFRACTORY PERIOD¹

Abstract

I. THE PROBLEMSMost tasks do not consist of reactions to single stimuli spaced at intervals of a few seconds; ordinarily, for example, when dealing with a control mechanism (as in tracking a moving target) the human being has to attempt to follow a continuous series of stimuli, or a continuously changing stimulus. Two main questions then arise:(1) Does the operator respond continuously or intermittently?(2) If he responds intermittently, how long is the psychological refractory period, i.e. how long must elapse after the presentation of one stimulus before a response can be initiated to the next stimulus in the series? Telford (1931) has already pointed out that in a rapid series of stimuli the ordinary reaction time to auditory signals can be increased by 0.1 sec. by reducing the time interval between stimuli from 1.0 to 0.5 sec. PRELIMINARY EXPERIMENTS : CORRECTIVE PERIODS IN TRACKING RECORDS(1) Procedure Experiment Z. In Fig. 1 A is reproduced a typical record obtained when the subject is required to wind a balanced handwheel at a constant speed. The aim of the subject was to maintain a pointer steady on a straight circumferential white line drawn on a rotating smoked drum. The pointer was actuated by a motor, so that it moved steadily away from the line, and required a compensatory movement of the handwheel at a rate of 1 r.p.m. to keep it on the line.Experiment ZZ. In Fig. 1, B, C and D show records made in carrying out similar tasks; but in these cases the pointer was actuated by a cam (three different cam courses were used and are shown in the record in each case), which caused the recording pointer to move according to a predetermined course. The subject could compensate for the pointer movements by moving a handle up or down, and his task was to keep the pointer on a horizontal white line previously drawn on the smoked drum.Experiment ZZZ. Using the apparatus of Experiment 11, and the cam course illustrated in Fig. 1 B, eight subjects were given the same task, a t five different drum speeds: 4,10, 20, 50 and 100 mm./sec.

Human Balance Control: Dead Zones, Intermittency, and Micro-chaos

“…However, it has long been speculated that there is a refractoriness in the execution of motor movements planned by the central nervous system such that corrective movements are made only intermittently [56,94,95]. Indeed the increased effectiveness of intermittent versus continuous feedback control has been demonstrated in a virtual stick balancing task [56].…”

“…In the case of stick balancing on the fingertip the intermittency manifests as a power law [12,19,75]. Second, the observed intermittency may reflect an intermittent motor control strategy [38,56,94,95,91]. Indeed control-theoretic considera-tions indicate that optimal control strategies in the presence of noise and delay are those in which corrective movements are made intermittently [75,92,93].…”

Backward compatibility effects in younger and older adults

“…Conversely, in many situations for each additional millisecond that the stimulus of the second task is delayed after the onset of the stimulus of the first task (the stimulus onset asynchrony or SOA), the reaction time (RT) to the second task drops by 1 ms. By contrast, the RT to the first task is largely unaffected by SOA. The slowing of the second task at short SOAs often is called the psychological refractory period (PRP) effect by analogy with the time after firing when a neuron is unresponsive to further input (Telford, 1931;Vince, 1948;Welford, 1952). The PRP effect has been replicated in a large number of experiments, thus deserving the status of one of the few laws of contemporary cognitive psychology.…”

Central interference in error processing

“…For example, in the psychological refractory period paradigm (cf. Vince, 1948;Welford, 1952;see Pashler & Johnston, 1998, for a review), researchers observed interference in the second of two speeded tasks when they were presented in rapid succession. According to Pashler and Johnston, interference arose because of limitations in parallel response selection, and it was assumed that sensory and perceptual processes of the two tasks were performed in parallel.…”