A. H. Tickner

Measurement of control skills, vigilance, and performance on a subsidiary task during 12 hours of car driving.

Eight subjects were given short driving tests at 0700, 1000, 1300, 1400. 1700 and 2000 hours on 2 days: (1) under experimental conditions of continuous driving and (2) under control conditions in which they carried on with their normal work between tests. Car control skills and performance on a subsidiary task of time-interval production were measured on a 2·2 mile test circuit in city traffic. Pulse rate and oral temperature were also recorded. Vigilance was measured during main-road driving on the experimental day by scoring time taken to respond to a light signal. Vigilance improved significantly during the spell of prolonged driving. Time-interval production was reliably more variable under experimental conditions than under control, but this difference was independent of the duration of the driving period. Differences in car-control skills between conditions were slight and statistically unreliable. These results support previous findings that a virtually continuous 12 hour period of driving during t...

Monitoring up to 16 Synthetic Television Pictures Showing a Great Deal of Movement

A total of 204 observes watched usually 16 synthetic television pictures for 1 hr. The 8 pictures in the middle 2 columns of the display showed activity inside prison. The 8 pictures in the 2 side columns of the display showed activity just outside prison walls. There were 14 suspicious incidents inside prison, 7 of them serious, and 170 other movements. Just outside prison there were fl auspicious incidents, 1 of them serious, and 5,300 other movements. The observer had to press an alarm button whenever he or she saw a suspicious incident. Suspicious incidents were missed reliably more often when they were in the distance, or of brief duration. When matched for distance and duration, incidents were missed reliably less often inside prison, where there was less other activity, than just outside prison. Inside incidents were missed reliably less often when only 8 inside pictures were watched, than when 4 inside and 4 outside pictures were watched- A telephone call about 10 see before an incident reliably reduced the proportion of detections. If more than 1 picture has to be watched, the maximum desirable number is about 9 when there is a lot of movement. The maximum desirable duration for a spell of work is about 1 hr. Reducing the size of pictures from 40 × 30 cm to 20 × 1.1 cm reliably reduced the proportion of detections. Halving the distance of the observer from the small pictures from 9 to 4-5 ft still left a reliable reduction in the proportion of detections of distant incidents. Observers under 30 yr detected reliably more incidents, and made reliably fewer false detections, than observers over 45yr. When matched for age, prison officers who had previously monitored television pictures were reliably better than prison officers who had not. The experienced prison officers detected reliably more suspicious incidents inside prison than did the civilian observers.

Watching for People and Actions

Abstract A total of 24 police officers and 156 civilians were shown a film of a street scene for 4, 2 or 1 hr. They had to watch for people and actions which had been inserted into the film deliberately. Photographs of the wanted people were mounted beneath the screen. In one condition a short colour film of each wanted person was shown before the main film. Three people were detected reliably more often when they were the only throe people to be watched for, than when they were among 12 people to be watched for. No advantage was gained by reducing the number from three to one. The three people were detected reliably less often when the film and photographs were in black and white than when the film was in colour, their photographs were in colour, and the film was proceded by a short colour film of each person. Stealing was detected reliably more often than the wanted person who did the stealing. Both people and actions were detected reliably more often when they were near the camera than when they were f...

An investigation into the effects of stress upon skilled performance.

An account is presented of an investigation of the effect of an anxiety-producing situation, namely the imminence of a parachute jump, upon skill in an acquisition tracking task. Parachutists at three levels of practice wore oxamined: 19 experienced Regular Army men, 9 Regular Army trainees, and 10 Territorial Army (TA) trainees. It was found that tho TA men were more affected (p <0.05) than the Regular trainees, who were more affected (p<0.001) than the experienced Regulars, who were not affected at all. It is concludod that anxiety does produce a decrement in tasks of this kind, although such decrements can be minimized by appropriate training. It is suggested that an investigation into the best form of such training might bo well worth whilo.

An Investigation into the Comparative Suitability of Forearm, Hand and Thumb Controls in Aquisition Tasks

Performance of subjects on a set of two-dimensional velocity control acquisition tasks was measured when the control was operated by thumb, hand, and forearm. Four control conditions—high and low sensitivity with 0 and 2 sec exponential lag—were used. Six groups, each of 6 naval ratings, acted as subjects; and the three limb-segments were compared under all conditions. It was found that, under the easiest condition, there was no significant difference between the controls; but in the most difficult, hand was superior to both forearm (p<0·001) and thumb (p<0·01), whilst thumb was superior to forearm (p<0·01).

Monitoring 16 Television Screens Showing Little Movement

Altogether 65 observers watched 16 or 24 television screens for L hr. The screens showed mainly still scenes from a prison, with occasional movements lasting 2 to 40 see. The observer had to press an alarm whenever he saw a suspicious incident. During the 1 hr there were 12 suspicious incidents and 72 other movements. Reliably more incidents wore missed when they were brief and indistinct, and when they were scattered over 24 screens instead of over only 16 screens. Having to report all movements, and having to answer questions about movements every 30 sec, also reliably increased the number of missed incidents. Having 24 screens to monitor instead of 16, and having to answer questions, reliably increased the time taken to press the alarm. Incidents were spotted more quickly if there had recently been a movement on an adjacent screen. Sitting nearer also reduced the time taken to press the alarm. The results conform to the principles of human performance derived from simpler experiments on visual vigilanc...

Remote Monitoring of Motorways Using Closed-Circuit Television

Abstract Three 1-hour films of moving traffic on the M1 motorway were used to present synthetic closed-circuit television pictures. Twelve police officers from a traffic division and 84 civilians monitored one or three simultaneous films, looking for vehicles parked on the hard shoulders. Over 75 per cent of incidents at or nearer than 440 yards were reported, compared with under 45 per cent of incidents at or beyond 660 yards (p<0·01). Incidents at 220 yards were detected on average more rapidly than incidents at 440 yards (p<0·01). Observers monitoring a single film reported incidents at 220 yards reliably more rapidly (p<0·02) than observers monitoring three simultaneous displays. This in turn gave reliably quicker reporting (p<0·05 or better) of incidents at 440 yards than the other conditions in which three films were monitored but only one was visible at a time. The police officers were better at the task than the civilians. More detailed analyses suggested that in monitoring more than one film, loo...

The Effect of Temporary Obscuration of the Target on a Pursuit Tracking Task

An account is presented of an experiment in which subjects performed a continuous tracking task with the moving target temporarily obscured during part of its course. It was concluded that (i) subjects pursuit is very poor during the obscured interval; but (ii) recovery of the target is very rapid thereafter. These conclusions held with both positional and velocity control systems.

An Investigation into the Effect of Exercising Particular Limb-Segments upon Performance in a Tracking Task

Abstract An account is presented of an investigation into the effect upon skill in an acquisition tracking task of exercising particular limb-segments. To carry out the task the operator used his thumb to operate a small joystick. Two sorts of exercise were employed: one used the muscles of the whole hand, the other principally those of the thumb. It was found that the latter produced a marked, though transient, decrement in performance, whereas the former did not. It appears that, for tasks of this typo and order of difficulty, serious decrement in performance is only to be expected when highly specific muscle groups are exercised. Normal work-loads and activities should not, therefore, constitute a hazard.

Identifying People in a Videotape Recording Made at Night

Two groups of 12 observers watched a 65 min videotape recording of a street scene at night. They had to identify five people whoso photographs were mounted below the 30 cm TV screen. For one group the photographs showed the people wearing the same outdoor clothes as on the night of the recording. For the other group the photographs showed the people wearing indoor clothes. People wore not identified by more than about half the observers unless they were within 12 or 15 m of the camera..This is about half the distance at which a similar proportion of identifications have been mode from iv film taken in daylight. Photographs of the people correctly dressed were found to aid identification. The fur hood worn by one person, and the spectacles with thick black rims worn by another person, aided identification and reduced false identifications. The throe older men observers did not take advantage of the cues which the correctly dressed photographs provided.