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31 drivers who had not been involved in a vehicle crash in the pre- of-view, field independence, attention sharing, and range of vious year. The frequent-crash group displayed more dichoto- motion. Sensory-motor tests such as these may be helpful in mous thinking than the infrequent-crash group. Dichotomous assessing medical conditions as well as alcohol and drug thinking involves polarizing events so that more extreme impairment (Llaneras et al. 1995). choices are selected as the appropriate course of action. The dichotomous thinker is more likely to make an inappropriate 4.9 OTHER RISK FACTORS choice in favor of extreme action when presented with a dan- gerous driving situation. This study lends moderate support for 4.9.1 Stress the view that extreme thinking is associated with crash risk. Stress is generally seen as a human response to an aver- sive or threatening situation, not as an enduring personal trait. 4.8 SENSORY-MOTOR PERFORMANCE However, if stressful situations are long-lasting or recur- rent, stress can become an individual characteristic. Height- As a dynamic sensory-motor task, driving performance is ened stress has been implicated in increasing the risk of obviously affected by physical abilities. Reliable percep- vehicle crashes. Brown and Bohnert (1968) reported that 80% tion, quick response, and accurate maneuvering are essen- of drivers involved in fatal crashes, but only 18% of controls, tial features of safe driving (Dewer 2002). However, if physical prowess were the primary factor influencing crash were under serious stress involving interpersonal, marital, involvement, then teenagers and young adults would likely vocational, or financial areas prior to the crash. Finch and be the safest drivers, and individual athletic prowess would Smith (1970) reported similar findings. Among the general correlate with driving safety. population of drivers, the association of alcohol with crash A 1998 study by Trucking Research Institute and Inter- involvement may reflect life stress as well as its direct dele- Science America provided an extensive and detailed list of terious effects on driving. Seltzer and Vinokur (1974) admin- driving-related sensory-motor abilities, as follows: istered self-report questionnaires assessing stressful life events (Holmes and Rahe's Life Events Checklist), alcohol Perceptual abuse (Michigan Alcoholism Screening Tests), several per- Static visual acuity (stationary objects) sonality variables (aggressions, paranoid thinking, depression, Dynamic visual acuity (moving objects) and suicidal tendencies), and driving history (exposure, viola- Contrast sensitivity tions, and accidents and crashes) with two groups of drivers. Useful field of view (area of visual field in which The general group comprised drivers renewing their drivers' information is acquired) licenses or completing driver safety school. The other group, Field independence (ability to perceive targets embed- called the alcohol group, comprised drivers receiving in- ded in a complex scene) patient or outpatient treatment for alcoholism. The Seltzer Depth perception and Vinokur found that drivers under greater social stress Cognitive (regardless of group) were correlated with more crashes Decision-making and other accidents. Subjective stress to life events was Selective attention (ability to attend to one stimulus more highly correlated with prior crashes and accidents while filtering out "noise") than either demographic and personality variables. McMur- Attention sharing ray (1970) found divorce to be a significant predictor of Information processing (ability to acquire information crash risk. In his study of 410 drivers involved in divorce and perform mental operations on it) proceedings, drivers had twice as many crashes during the Psychomotor year of their divorce than during 7 previous years. This rate Reaction time was even higher for the period 6 months before and after the Multi-limb coordination divorce. These studies provide support for an association of Control precision life stressors and crash risk, with alcohol use as a frequent Tracking (follow a path or pursue a moving target) concomitant factor. Range of motion In the research project survey, the stress-related driver situa- This study on five different older commercial driver groups tions, "unhappy/disgruntled with job or company," "debt or was conducted to examine the impact of increasing age on other financial problems," and "unhappy marriage or other perceptual, cognitive and psychomotor abilities, and driving family problems" were generally rated near the middle of the 16 surveyed factors in terms of their association with crash risk. performance. Age, in and of itself, was not reliably predictive of driving performance. One reason was that the individual variation within age groups was much greater than the varia- 4.9.2 Recent Involvement in Other Crashes tion across groups. Tests comparing driver performance on the above sensory-motor tasks with performance on an inter- One source of stress might be recent involvement in a crash. active commercial truck driving simulator indicated that the A recent crash might also be an indication that a driver is not most predictive abilities were depth perception, useful field- performing safely during the time period in question. Blasco,