The double-drift illusion produces a large deviation in perceived direction that strongly dissociates physical position from perceived position. Surprisingly, saccades do not seem to be affected by the illusion (Lisi & Cavanagh, 2015). When targeting a double-drift stimulus, the saccade system is driven by retinal rather than perceived position. Here, using paired double-drift targets, we test whether the smooth pursuit system is driven by perceived or physical position. Participants (n = 7) smoothly pursued the inferred midpoint (Steinbach, 1976) between two horizontally aligned Gabor patches that were separated by 20° and moving on parallel, oblique paths. On the first half of each trial, the Gabors' internal textures were static while both drifted obliquely downward. On the second half of each trial, while the envelope moved obliquely upward, the internal texture drifted orthogonally to the envelope's motion, producing a large perceived deviation from the downward path even though the upward and downward trajectories always followed the same physical path but in opposite directions. We find that smooth pursuit eye movements accurately followed the nonillusory downward path of the midpoint between the two Gabors, but then followed the illusory rather than the physical trajectory on the upward return. Thus, virtual targets for smooth pursuit are derived from perceived rather than retinal coordinates.

中文翻译：

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平滑追踪在双漂移刺激的感知而非物理位置上运行。

双漂移错觉会在感知方向上产生很大的偏差，从而强烈地将物理位置与感知位置分离。令人惊讶的是，眼跳似乎不受错觉的影响（Lisi & Cavanagh, 2015）。当针对双漂移刺激时，扫视系统由视网膜而不是感知位置驱动。在这里，使用成对的双漂移目标，我们测试平滑追踪系统是由感知还是物理位置驱动。参与者 (n = 7) 顺利地追踪了两个水平对齐的 Gabor 斑块之间的推断中点 (Steinbach, 1976)，这些斑块相隔 20°，并在平行的倾斜路径上移动。在每次试验的前半部分，Gabors 的内部纹理都是静态的，而两者都倾斜向下漂移。在每次试验的后半段，当包络线倾斜向上移动时，内部纹理与包络线的运动正交漂移，即使向上和向下的轨迹始终遵循相同的物理路径但方向相反，也会产生与向下路径的较大感知偏差。我们发现平滑的追踪眼球运动准确地跟随两个 Gabor 之间中点的非虚幻向下路径，但随后在向上返回时跟随虚幻而不是物理轨迹。因此，平滑追踪的虚拟目标来源于感知而不是视网膜坐标。即使向上和向下的轨迹始终遵循相同的物理路径但方向相反，也会产生与向下路径的较大感知偏差。我们发现平滑的追踪眼球运动准确地跟随两个 Gabor 之间中点的非虚幻向下路径，但随后在向上返回时跟随虚幻而不是物理轨迹。因此，平滑追踪的虚拟目标来源于感知而不是视网膜坐标。即使向上和向下的轨迹始终遵循相同的物理路径但方向相反，也会产生与向下路径的较大感知偏差。我们发现平滑的追踪眼球运动准确地跟随两个 Gabor 之间中点的非虚幻向下路径，但随后在向上返回时跟随虚幻而不是物理轨迹。因此，平滑追踪的虚拟目标来源于感知而不是视网膜坐标。