Wertheim Alexander H, Paffen Chris L E
Helmholtz Institute and Department of Experimental Psychology, Utrecht University, Heidelberglaan 2, 3584-CS Utrecht, The Netherlands.
Perception. 2009;38(11):1610-20. doi: 10.1068/p6387.
In the Freezing Rotation illusion a stimulus rotating with a constant velocity is perceived as stationary on the screen, when it is presented in front of a background pattern that moves with a sinusoidal velocity profile, during the phase in which stimulus and background rotate in the same direction. It has been suggested that this illusion is caused by the interfering effect of induced motion resulting from the relative motion between the centre and the surround. Since the magnitude of such an induced motion component presumably relates to the difference between background and centre velocities, the illusion itself should also be related to the amount of relative motion between the centre and the surround, and it should not occur when this difference is zero. We present evidence here that this hypothesis is incorrect. First, we show that the illusion also occurs when the background moves with a constant velocity instead of sinusoidally. Second, we show that the illusion consists of a fixed underestimation of centre velocity when the centre and the surround move in the same direction and a fixed overestimation of centre velocity when they move in opposite directions or when the background remains stationary. The amount of underestimation and overestimation of velocity is not related to the velocity difference between the centre and the surround. Some factors that may be relevant to the explanation of the illusion are discussed.
在冻结旋转错觉中，当一个以恒定速度旋转的刺激物呈现在以正弦速度分布移动的背景图案前，且在刺激物和背景沿相同方向旋转的阶段，该刺激物会被视为在屏幕上静止不动。有人认为这种错觉是由中心与周围环境之间的相对运动所导致的诱导运动的干扰效应引起的。由于这种诱导运动成分的大小大概与背景和中心速度之间的差异有关，那么错觉本身也应该与中心和周围环境之间的相对运动量有关，并且当这种差异为零时错觉不应出现。我们在此提供证据表明这一假设是错误的。首先，我们表明当背景以恒定速度而非正弦方式移动时，错觉同样会出现。其次，我们表明错觉包括当中心和周围环境沿相同方向移动时对中心速度的固定低估，以及当它们沿相反方向移动或背景保持静止时对中心速度的固定高估。速度的低估和高估程度与中心和周围环境之间的速度差异无关。我们还讨论了一些可能与解释该错觉相关的因素。
