Effect of Cold and Rain Upon the Vigilance of Lookouts

Sixteen men performed lookout duties twice at sea in winter on an open bridge, once in the Arctic (mean temperature 28°F) and once in a mores temperate clime (mean 37F°) in counterbalanced order. The 2 signal sources were separated by an angle of 75° and presented 7 signals each in an irregular order and at irregular intervals during a 30-minute watch. The lookout had to respond as soon as he saw a signal. There were reliably more response times of 20 seconds or longer in rain than in the cold (p < -01). There was a reliable increase in the number of long response times during the watches in the cold (p < -01) accompanied by a mean fall in oral temperature of 12°F.