Koenderink Jan J, van Doorn Andrea J, Lappin Joseph S
Utrecht University, Faculteit Natuur- en Sterrenkunde, Princetonplein 5, 3584 CC Utrecht, Netherlands.
Acta Psychol (Amst). 2003 Jan;112(1):71-87. doi: 10.1016/s0001-6918(02)00101-4.
We use an exocentric pointing task to study exocentric visual directions to targets that are opposite to a pointer relative to the observer. (The apparent distance between the target and the pointer always exceeded 90 degrees of visual angle.) All pointing takes place in the horizontal plane at eye height. Observers could not see both target and pointer at a single glance. They had to look back and forth between them, using combinations of eye movements, head turns, twists at the waist and turning on the feet. In the limit of diametrically opposite targets we find that the observers pick either one of two distinct orientations of the pointer as equally "visually correct". Which one results depends on the stance assumed by the observer. The difference between the two equally acceptable pointings is between 5 degrees and 10 degrees. Such a result is predicted from earlier measurements in the context of a model that describes the geometry of the horizon as a Riemannian space with varying intrinsic curvature. The present results thus fit--perhaps surprisingly--very well in such a picture.
我们使用一种外心指向任务来研究相对于观察者而言与指针方向相反的目标的外心视觉方向。（目标与指针之间的视距始终超过90度视角。）所有指向操作均在与眼睛等高的水平面上进行。观察者无法一眼同时看到目标和指针。他们必须在两者之间来回看，通过眼球运动、头部转动、腰部扭转和原地转身等动作组合来实现。在直径相对的目标的极限情况下，我们发现观察者会将指针的两种不同方向中的任意一种视为同样“视觉上正确”。最终选择哪一种取决于观察者所采取的姿势。两种同样可接受的指向之间的差异在5度到10度之间。在一个将地平线几何形状描述为具有变化内在曲率的黎曼空间的模型背景下，根据早期测量结果可以预测到这样的结果。因此，目前的结果——也许令人惊讶——在这样的图景中非常吻合。
