Neuropsychological driving fitness tests for brain-damaged subjects.

OBJECTIVES: The study was carried out to evaluate and develop simple tools to assess the driving fitness of brain-damaged patients. DESIGN: Four neuropsychological tests (predictors) were validated against an open-road driving test (criterion standard), which is used by the Department of Adaptations of the Dutch Driving Licensing Agency for assessing disabled drivers. SETTINGS: The predictor tests were conducted in the involved scientific institute; the criterion standard involved participation in normal traffic. PATIENTS: The subject group consisted of 33 men and 5 women who had recovered to a stabilized level from traumatic brain injuries. All had valid driving licenses when they were injured and they were considered to be potentially able to recommence driving. The subjects had a mean reported driving experience of 109.200km (SD = 86.300km). All subjects were recovered from a brain trauma with an average coma duration of 33 days (SD = 51 days). They were tested at least 1 year after the accident. All the subjects had normal or corrected-to-normal vision and none used medications that, according to existing medical criteria, interfere with normal psychomotor or cognitive functioning. Ages at the time of the injury were between 17 and 55 years (mean, 29.8; SD, 10.9). MAIN OUTCOME MEASURES: Pearson product moment correlations (and explained variances) were calculated between the four predictor tests (a Perceptual Speed test, the WAIS Symbol-Digit Substitution subtest, a Tracking-Reaction dual task, and a Time Estimation task) and the open-road criterion standard. RESULTS: The results indicated that performance on both the Perceptual Speed task and the Time Estimation task were significantly correlated with driving performance (p < or = .05). When combined with coma duration and driving experience, the Perceptual Speed and Tracking-Reaction tests together explained 35.3% (r = .59) of the variance in on-road driving performance. CONCLUSIONS: The amount of variance in open-road driving performance that could be accounted for by these tests was insufficient to completely replace an open-road driving fitness assessment. Also, based on other experimental documentation, it is concluded that more integral, domain-specific test (eg, based on driving simulation) need to be developed.

Reducing color-color interference by optimizing selection for action.

Color-color interference refers to the finding that the naming of a target color is hampered by the simultaneous presentation of an incongruent distractor color somewhere else in the visual field. This interference effect has been attributed to an imperfect input selection (selection-for-processing). We test an alternative account in which it is assumed that (a) target and distractor are identified in parallel without mutual interference, (b) the identified target color has to be selected to control the naming response (selection-for-action), and (c) this selection process takes more time and is less accurate in the incongruent condition than in the control conditions. Experiment 1 shows that color-color interference obtained when a target color, presented at the point of fixation, is flanked by incongruent colors. In Experiments 2 and 3, the central target position is indicated by an additional exogenous selection cue. The results show that an abrupt-onset cue, presented at the central target position 160 ms after the onset of the target and distractors, reduces the interference effect. This finding is interpreted as supporting evidence for a selection-for-action account of color-color interference.