Baurès Robin, Hecht Heiko
Department of Psychology, Johannes Gutenberg-Universität Mainz, Mainz, Germany.
Perception. 2011;40(6):674-81. doi: 10.1068/p6945.
On Earth, gravity accelerates freely moving objects downward, whereas upward-moving objects are being decelerated. Do humans take internalised knowledge of gravity into account when estimating time-to-contact (TTC, the time remaining before the moving object reaches the observer)? To answer this question, we created a motion-prediction task in which participants saw the initial part of an object's trajectory moving on a collision course prior to an occlusion. Observers had to judge when the object would make contact with them. The visual scene was presented with a head-mounted display. Participants lay either supine (looking up) or prone (looking down), suggestive of the ball either rising up or falling down toward them. Results showed that body posture had a significant effect on time-to-contact estimation, but only when occlusion times were long (2.5 s). The effect was also rather small. This lack of immediacy in the posture effect suggests that TTC estimation is initially robust toward the effect of gravity, which comes to bear only as more time is allowed for post-processing of the visual information.
在地球上，重力使自由移动的物体向下加速，而向上移动的物体则减速。人类在估计接触时间（TTC，即移动物体到达观察者之前剩余的时间）时，是否会考虑内化的重力知识呢？为了回答这个问题，我们创建了一个运动预测任务，在该任务中，参与者在遮挡之前看到物体在碰撞轨道上移动的初始部分。观察者必须判断物体何时会与他们接触。视觉场景通过头戴式显示器呈现。参与者要么仰卧（向上看）要么俯卧（向下看），这暗示着球是朝着他们上升还是下降。结果表明，身体姿势对接触时间估计有显著影响，但仅在遮挡时间较长（2.5秒）时才会如此。这种影响也相当小。姿势效应缺乏即时性表明，TTC估计最初对重力效应具有较强的抗性，只有在有更多时间对视觉信息进行后期处理时，重力效应才会起作用。
