Simulating time-to-contact when both target and observer are in motion

We examined the effect of observer motion on perceived time-to-contact (TTC) with an approaching target simulated on a wide-field display. In Experiment 1, we compared observer motion (OM) alone with target motion (TM) alone, and found that TTC estimates were significantly shorter for OM even though the value of τ was the same in both cases. In Experiment 2, we compared TTC estimates for different combinations of OM and TM, and found that estimated TTC decreased as the proportion of OM was increased. The present data are further evidence that TTC estimates are not based solely on visual cues (e.g., τ) associated with the rate of optical expansion of a target, and further suggest that, for more complex imagery, display-related information such as optical flow can contribute independently to perceived TTC.