Effects of Age-Related Declines in Visual Motion Processing on Older Driver Safety

This thesis reports three experiments investigating how age-related declines in visual motion processing affect older drivers’ ability to drive safely. In particular, these experiments assess the efficacy of: 1) A test of motion sensitivity, the Peripheral Motion Contrast Threshold (PMCT) test, which evaluates ones’ contrast threshold for detecting motion in the periphery, and 2) the 3D multiple-object tracking test (3D MOT), which evaluates the maximum stimulus speed at which one can maintain visual attention on several objects moving in three dimensions. Two versions of the PMCT test—the PMCT-10 and the shorter PMCT-2—were employed. Driving safety was measured via a high fidelity driving simulator, in addition to several self-report measures and archival data. Study 1 showed that PMCT-2 and PMCT-10 thresholds were associated with number of crashes in the simulator and other indices of unsafe driving. Study 2 examined whether the PMCT-2 could predict older driver performance during a different set of simulated driving scenarios, and whether it was associated retrospectively with real world crash rates. PMCT-2 results were significantly correlated with simulated crash risk. Moreover, Study 2 provided the first evidence that PMCT scores are associated with real-world crash, albeit in a small retrospective sample. Study 3 examined the relationship between results from both the PMCT-2 and 3D MOT tests and simulated driving. Multiple object tracking has previously been associated with older drivers' performance. Results showed a strong relationship in our sample between crash rates and 3D MOT results. However, we failed to replicate the results showing a relationship between PMCT and crash occurrence. This may have been due to high rates of subject attrition due to simulator sickness, which resulted in a small final sample. Overall, findings from the three studies demonstrate that results from PMCT and 3D MOT are associated with older drivers’ performance measures, such as crash rates, dangerous lane deviations, and speeding. These findings support visual motion processing measures as viable candidates for inclusion in a multi-domain assessment of older drivers’ fitness to drive