Efficiency at Sorting Cards in Compressed Air.

At a site where compressed air was being used in the construction of a tunnel, 34 men sorted cards twice, once at normal atmospheric pressure and once at 3j, 2j, or 2 atmospheres absolute pressure. An additional six men sorted cards twice at normal atmospheric pressure. When the task was carried out for the first time, all the groups of men performing at raised pressure were found to yield a reliably greater proportion of very slow responses than the group of men performing at normal pressure. There was reliably more variability in timing at 3j and 2i atmospheres absolute than at normal pressure. At 31 atmospheres absolute the average performance was also reliably slower. When the task was carried out for the second time, exposure to 31 atmospheres absolute pressure had no reliable effect. Thus compressed air affected performance only while the task was being learnt; it had little effect after practice. No reliable differences were found related to age, to length of experience in compressed air, or to the duration of the exposure to compressed air, which was never less than 10 minutes at 31 atmospheres absolute pressure.