A New Device to Measure Drug-Induced Changes on Reactive and Coordinative Skills of Human Performance

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Abstract
A computerized device for simultaneous measurement of coordinative and reactive skills related to driving was developed and tested in two consecutive trials of psychoactive agents in healthy volunteers. The test system comprises a vehicle, a driving computer (Sinclair QL), and the programming and measurement computer (IBM‐PC). The computerized driving programme projects to the colour ‐ TV screen a winding road, and the driver has to keep the car on the road by turning the steering wheel. The driving proceedes at a fixed, fairly rapid rate for 5 min., and the numbers of tracking errors (deviations from the road) as well as the tracking percentage (relative length of the track driven off the road) were computed separately for both halves of the track. During the latter half of the track 60 visual or/and sound stimuli were given in random order, and the driver had to respond or not respond to them by pressing a button or by pushing a foot pedal. The number of reaction errors and the cumulative reaction time were recorded. The programme also provides a histogramme that relates the number of deviations from the road to their duration, enabling a visual judgement of the severity of errors. Matched versions (mirror image, reverse direction) of tracks of varying severity were offered to reduce learning effect during the trial. When testing the device in two placebo‐controlled double‐blind and cross‐over trials, a considerable practice effect on tracking and reaction strategies took place, but after proper training the baselines remained reasonably stable. In spite of the practice effect an impairment of coordinative skills by lorazepam 2.5 mg or by diazepam 15 mg was demonstrated whereas ethyl alcohol 0.8 g/kg impaired reactive skills more than eye to hand coordination. Additive drug‐drug and drug‐alcohol combined effects were found.

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