Judgments of absolute time-to-contact in multiple object displays: evaluating the role of cognitive processes in arrival-time judgements



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Texas Tech University


Time-to-contact (TTC) is the time it takes for a moving object to contact a designated point. Recent studies suggest that task variables determine whether cognitive processes influence TTC judgments and that such processes may contribute to TTC estimation in prediction motion (PM) tasks. In PM tasks, an object moves toward a point and disappears; observers judge when they think the object would have reached the point assuming constant velocity. Prior research indicates that estimation errors increase as TTC increases which may reflect a deterioration in cognitive processes such as memory.

To evaluate the potential role of cognitive processes in PM tasks, this study included multiple objects. Computer simulations of one, three, or six objects (set-size) moved laterally and disappeared before contacting a finish line. A post-cue appeared immediately, 1.5 or 3 s, after the objects disappeared (post-cue delay) and indicated the target object Participants responded when they thought the target would have contacted the finish line. Performance was hypothesized to degrade as cognitive load increased (operationally defined by increases in set-size and post-cue delay).

Accuracy decreased as set-size increased for the smaller of two actual TTCs in each experiment (I but not 3 s in Experiment 1; 4 but not 6 s in Experiments 2 and 3). Thus, performance consistent with limited cognitive processing was evident when estimating certain TTC values. Additionally, when both set-size and post-cue delay were varied (Experiment 2), accuracy decreased as set-size and post-cue delay increased regardless of TTC, consistent with limited cognitive processes. Furthermore, conditions that produced decreases in accuracy also resulted in an increase in TTC estimation. The latter can be regarded as an increase in response time which is consistent with limits in cognitive processing.

In conclusion, this study provides some evidence that limits in cognitive processing affect performance in PM tasks. The effect of post-cue delay could reflect limits in maintenance of an internal representation or memory. However, further study is needed to determine the exact nature of cognitive processes that are potentially used in PM tasks. Results have implications for models of perceived collision and application to transportation safety.