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.