Gray R, Regan D
Nissan Cambridge Basic Research, MA 02142, USA.
Perception. 1999;28(10):1257-64. doi: 10.1068/p2895.
Motivated by the debate between indirect and direct theories of perception, a large number of researchers have attempted to determine whether judgments of time to collision are based on the ratio of perceived distance to perceived speed or on the ratio theta/(d theta/dt), i.e. tau. Despite the considerable research effort devoted to this question there seems to be no clear resolution. We used a staircase tracking procedure to estimate errors in estimating time to collision for a simulated approaching object. To investigate the role of perceived distance in the judgment of time to collision, we asked observers to alternate between two viewing distances (100 and 500 cm). For the 500 cm viewing distance, we magnified the visual display by a factor of five so that the retinal images [and the values of theta/(d theta/dt) through time] were identical for the two viewing distances. All visual cues to distance were available. There were no significant differences between estimates of time to collision made at the two viewing distances. We conclude that our observers ignored perceived distance when estimating time to collision and based their responses on theta/(d theta/dt). We concur with recent proposals that, in the future, time-to-collision research should move away from the either/or analysis of different information sources that has dominated previous studies towards investigations of how different information sources are integrated.
受知觉间接理论与直接理论之间争论的推动，大量研究人员试图确定对碰撞时间的判断是基于感知距离与感知速度的比值，还是基于θ/(dθ/dt)的比值，即τ。尽管针对这个问题投入了大量研究精力，但似乎仍没有明确的结论。我们使用了一种阶梯跟踪程序来估计对模拟接近物体的碰撞时间估计中的误差。为了研究感知距离在碰撞时间判断中的作用，我们要求观察者在两个观察距离（100厘米和500厘米）之间交替。对于500厘米的观察距离，我们将视觉显示放大了五倍，以便两个观察距离的视网膜图像[以及随时间变化的θ/(dθ/dt)值]相同。所有距离的视觉线索都是可用的。在两个观察距离下对碰撞时间的估计之间没有显著差异。我们得出结论，我们的观察者在估计碰撞时间时忽略了感知距离，并根据θ/(dθ/dt)做出反应。我们赞同最近的提议，即在未来，碰撞时间研究应从以往主导研究的对不同信息源的非此即彼分析，转向对不同信息源如何整合的研究。
