Leslie Buck

Motor performance in relation to control-display gain and target width

Five groups of subjects performed a target alignment task using a joystick-oscilloscope system with different control-display gains. Time taken to move to the target depended upon the width of the area into which the joystick had to be placed in order to align the target, while time taken to correct overshoots depended upon that factor and also the width of the target area on the oscilloscope. Movement precision as measured by overshoot rate depended upon target location and not upon target width whether measured on the joystick or oscilloscope. There was evidence of a movement time-overshoot rate trade-off. The results call into question recent views on the significance of control-display gain in the design of the operator-machine interface.

Boundary Distance Effects on Overshooting

Experiments with a subject-paced pursuit tracking task show that overshoot rate is dependent upon the distance between the target and the display boundary measured in the direction of movement, and that a previously noted inverse relationship with distance to the target is artifactual. The effect held for tasks with direct and reverse control-display relations, and for tasks with constant and variable target distances. The findings were consistent with Wetfords (1968) hypothesis that a pursuit response is initiated with a ballistic, distance-covering, movement. Ralph Leonardo carried out extensive work in collecting data, Fred Hyde maintained the apparatus, and Georgie Green assisted in data analysis.

THE EFFECTS OF TOLUENE AND ALCOHOL ON PSYCHOMOTOR PERFORMANCE

Eight male subjects took part in four experimental sessions in an exposure chamber to assess the effects of toluene (80 p.p.m.) and alcohol (0.4 ml per kg body weight) individually and in combination on four measures of performance and also on mood. Alcohol caused a significant deterioration over the exposure session in performance on pursuit tracking and visual search tasks and also in mood. Toluene had no significant effect on any of the behavioural measures, but examination of mean scores for each treatment suggested a tendency for performance and mood to deteriorate more when alcohol and toluene were administered together than when alcohol was taken alone.

Circadian rhythms in step-input pursuit tracking

Subjects performed a stop-input pursuit tracking task at regular intervals over two clays. Performance varied with time of day in a manner and to an extent dependent upon the choice of index so that circadian rhythms for speed scores were in inverse phase with those for accuracy scores. Presence or absence of knowledge of results made no significant difference to the time of day effect but increased short term memory demands disturbed the movement time rhythm supporting the hypothesis that psychomotor and short term memory functions vary in inverse phase with time of day.

Target location effects in tapping tasks

Abstract Previous experiments on tracking have shown that target location (measured in terms of the distance of the target from the boundary circumscribing the area of movement) affects the speed and accuracy of movement. The present experiment examined the effects of boundary distance on the speed and accuracy of tapping. Subjects performed on two-, three- and five-position tasks varying in movement amplitude and target width. Results showed that movement time increased, and constant error became more positive as boundary distance increased. These results differed from those found in respect of pursuit tracking in that constant error was affected and not variable error. They increase the generality of the finding that motor performance varies with target location, and they support theories of motor control implicating target location.

Defining the boundary in a positioning task.

Abstract Previous experiments have shown that overshoot rate in a linear positioning task is determined by the distance of the target from the boundary of the task in the direction of movement. Present experiments have served to specify distance more precisely as being relative rather than absolute, and as proximal rather than distal, and to show that the position of the boundary depends on the movements demanded by the task and not the visual and proprioceptive limits of the display. The operational boundary may be regarded as a cognitive construct by reference to which subjects locate targets.

Sleep loss effects on movement time

Subjects were tosted on a subject-paced step-tracking task three times every four hours under both of two regimes: one in which they slept for 6:30 hours at night and one in which they remained awake. 12 subjects were tested for two days under each condition, and 8 subjects for three days. Reaction times for correct responses increased following sleep loss to an oxtont inversely related to signal probability. Movement times increased following sleep loss to a much greater extent. It is concluded that movement time is a more sensitive index of performance deterioration due to sleep loss and that movoment time and reaction time represent separate processes.

location Versus Distance in Determining Movement Accuracy

In a pursuit-tracking task consisting of 100 positioning movements between targets at 5 fixed positions, target location (proximity to the boundary of the task) varied independently of movement amplitude. Eighty-seven subjects performed 12 trials of the task, with target width (at 3 levels) as a between-subject variable. A microprocessor system detected the location of the end-point of each primary movement. Movement accuracy (measured as end-point dispersion not constant error) varied with target location but not movement amplitude, while movement time varied with both factors. The effect of target width on movement accuracy was less consistent. The observed effects are discussed in terms of a mass-spring model of muscular action. It is concluded that apart from having important consequences for the design of positioning experiments, these results call into question information-processing and impulse-variability theories which implicate movement amplitude in determining movement accuracy, and support theories which emphasize target location.

The sensory basis of target location

Overshoot rate in a target alignment task depends on the location of the target with reference to the operational boundary of the task. Subjects performed a step tracking task under four conditions combining pursuit and compensatory display modes with joystick and crank control devices. The boundary effect was found when the joystick was used but not the crank, while the display mode had no effect, indicating that subjects moved with respect to a frame of reference based on proprioceptive information. Movements were made according to the postures adopted, irrespective of the concomitant visual consequences.

Comparing two methods of informing operators about what might happen next

Operator performance is dependent upon the level of certainty of what will happen next. Knowledge about this certainty can be given by long-term experience of the occurrence of events or by secondary information given immediately before the event. We define these methods as, respectively, memory-dependent and display-dependent. In this experiment nine groups of twelve subjects performed four-choice finger-pressing tasks in response to visual signals. The tasks were based upon the unbalanced frequencies and response priming paradigms of experimental psychology corresponding to the two methods of providing information thus defined. The tasks varied in mean certainty as well as in source of knowledge about the certainty. Mean reaction times varied, to a statistically significant degree, with level of certainty and, for events of low certainty, with the method of presenting information about certainty. Error rates varied inversely with the same factors but not all differences in this respect were statisticall...