The Influence o f Sex and Personality Factors upon the Effects of Tranquillizers on Driving Performance

There is a growing literature on the effects of psychotropic drugs on driving behaviour, reflecting increased concern that such drugs may have a similar role to alcohol in contributing to the causation of road accidents. However, the problems associated with experiments using psychotropic drugs are many times more complex than similar research using alcohol. Firstly, the task itself, driving a motor vehicle, involves a variety of cognitive, perceptual, and motor skills. Brown et al (3), for example, particularly distinguishes between control and decision skills and it is also known that failures in decision skills are of much greater importance in the causation of accidents than failures in control skills (4). These skills may well be subserved by different cognitive or physiological struc­ tures, which, in turn, may be selectively responsive to certain drugs. Thus, the effects of drugs may be quite specific to certain skills rather than having global effects upon driving. Hence, it is of crucial importance that the components of the real-life driving situation being studied should be chosen appropriately. Furthermore, individual differences such as sex and personality factors may lead to unique individual responses to a drug. Sex differences have been well documented in many fields. Human psychopharmacology is a notable exception. Most experiments in this field use all male subjects or unspecified mixed groups. However, there is no valid reason why there should not be marked sex differences in psychotropic drug responses. likewise, personality factors have been shown to influence performance in a wide range of experimental and real-life situation (7), but again they have received scant attention in the drugs and driving field, although a few studies have considered their interaction with alcohol (5).