Prediction equations for simple and visual two-choice reactions times in environmental neurotoxicology

To provide preliminary prediction equations for simple visual and two-choice visual reactions times, timed from the appearance of the letter A or S on a computer screen to cancellation, we modeled 264 randomly selected subjects from voter registration rolls in Arizona and Louisiana. These predicted values, validated by comparison to observed values and coefficients, were compared with those from a second population in California. We tested ability to detect abnormality by measuring a trichloroethylene-exposed population aged 17-70 y. The natural logarithm of simple visual reaction time was independent of age and other factors. The natural logarithm of two-choice visual reaction time was increased by age. These equations predict performance of groups that are studied with respect to neurobehavioral effects of chemicals, and the equations distinguish exposure and nonexposure for the range of adult ages. To define abnormality of individual subjects, we suggest use of the predicted value, plus 1.5 standard deviations; in this study, 8% of the model group was selected as abnormal.