The combined effects of occupational health hazards: an experimental investigation of the effects of noise, nightwork and meals.

An experimental study of the effects of noise, nightwork and meals showed that these factors influenced different aspects of performance. Speed of performing a low memory load version of a visual search task was influenced by working at night but was unaffected by either noise or meals. A high memory load version of the search task was performed more slowly after consumption of a meal, both during the day and at night, but was not influenced by nightwork. Subjects working in noise produced more errors on the high memory load task than those working in quiet, but neither nightwork nor meals had significant effects on the number of errors. The only evidence of an interaction between factors was obtained in the high memory load search task, where noise reduced the size of the post-meal decline in speed. These results show that the effects of noise, nightwork and meals are largely independent, the exception being the beneficial effect of noise on post-lunch performance. They also demonstrate that the effects of all of these factors depend on the nature of the task being performed, and on whether speed or accuracy is the variable under consideration.