Age-related differences in timing of position and velocity identification

The aim of this investigation was to study age-related differences in timing of position and velocity identification in a laboratory task. The skills required for performing this task are thought to be similar to those needed in real traffic situations. From this perspective, the results of this study may be taken into account in studies on accident analysis and prevention. To control for differences in the conscious experience of time and for simple reaction time to visual stimuli, young (25–34) and old (58–70) adults had to produce timed periods of 20 seconds and to time the arrival of a visible moving object at its goal. In these simple tasks no differences were found between young and old subjects. In the proper, more complex experiment, timing of position and velocity identification of a moving object were assessed with or without feedback on timing and velocity in the same old and young group. The object, moving from left to right at a constant velocity, was shown on a video screen during the first 40% of its trajectory. The moving object could have any of four (fixed) velocities which were presented in blocks with a regular or a mixed order. By pushing a button subjects estimated at which time the object would have reached the marked end of a trajectory. In a condition without feedback on timing of position, the timing error of older adults was higher than that of young adults and particularly with higher object velocities. In the condition with mixed velocities, subjects also had to indicate which of four velocities they thought was presented. Paradoxically, the older subjects now significantly over-estimated velocity. Possible explanations for these findings are considered