Shepard R N, Metzler J
Science. 1971 Feb 19;171(3972):701-3. doi: 10.1126/science.171.3972.701.
The time required to recognize that two perspective drawings portray objects of the same three-dimensional shape is found to be (i) a linearly increasing function of the angular difference in the portrayed orientations of the two objects and (ii) no shorter for differences corresponding simply to a rigid rotation of one of the two-dimensional drawings in its own picture plane than for differences corresponding to a rotation of the three-dimensional object in depth.
人们发现，识别出两幅透视图描绘的是具有相同三维形状的物体所需的时间：（i）是这两个物体所描绘方向的角度差的线性递增函数；（ii）对于仅相当于二维图形之一在其自身画面平面内的刚体旋转所对应的差异，并不比对三维物体深度旋转所对应的差异所需时间更短。
