Graduate School of Design and Architecture, Nagoya City University Nagoya, Japan.
Front Hum Neurosci. 2014 Jun 17;8:422. doi: 10.3389/fnhum.2014.00422. eCollection 2014.
In the self-touch illusion (STI), some can feel that both hands are touching each other even when they are separated actually. This is achieved by giving synchronized touches to both hands. Because the STI involves both hands (an administrating hand and a receptive hand) of a single person, two types of proprioceptive drifts (PDs) simultaneously occur in such a way that both hands are attracted to each other. It is known that the PD distance is generally larger for the administrating hand than for the receptive hand when the two hands are uncrossed. However, it remains unclear why such an asymmetrical relationship is observed universally. In this study, we conducted two types of experiment to induce the STI. The first experiment involved four conditions combining a factor of "whether the hands are uncrossed or crossed" and a factor of "whether the administrating hand is resting or active on the surface," with the receptive (left) hand located at the body's midline. The result demonstrated that crossing hands and resting on surface (ROS) induced the STI. Specifically, crossing hands enhanced the amount of PD distance by more than two or three times. Moreover, it is interesting that strong PD with dominance of the receptive hand, which did not appear in the uncrossed condition, was observed frequently. The second experiment collected seven "illusion-sensitive" participants from the first experiment, all of whom had a strong tendency to feel the self-touch, and examined the effect of the location of the body midline on the PD when hands are crossed with the administrating hand ROS. The result demonstrated that the dominant hand on the PD completely differed among participants, but was relatively stable over the midline position and time in the same person. We also found that a small number of participants exhibited quite a different pattern of the PD in the identical posture. On the basis of the results, we analyze in detail how the dominant hand on the PD is determined in the STI.
在自我触摸错觉（STI）中，有些人即使双手实际上分开了，也能感觉到它们在互相触摸。这是通过同时给双手同步触摸来实现的。因为 STI 涉及到一个人的双手（施动手和接受手），所以会同时出现两种类型的本体感觉漂移（PD），从而使双手相互吸引。已知当双手不交叉时，PD 距离通常对于施动手比接受手更大。然而，为什么会普遍观察到这种不对称关系仍然不清楚。在这项研究中，我们进行了两种类型的实验来诱导 STI。第一项实验涉及四个条件，结合了“双手是否交叉”和“施动手是否在表面上休息或活动”的因素，接受手（左手）位于身体中线。结果表明，交叉双手和在表面上休息（ROS）会诱导 STI。具体来说，交叉双手使 PD 距离增加了两倍或三倍以上。此外，有趣的是，在不交叉的情况下没有出现的优势接受手的强烈 PD 经常出现。第二项实验从第一项实验中收集了七个“错觉敏感”参与者，他们都强烈倾向于感觉到自我触摸，并检查了当双手交叉并施动手 ROS 时身体中线位置对 PD 的影响。结果表明，PD 上的优势手在参与者之间完全不同，但在同一人的中线位置和时间上相对稳定。我们还发现，少数参与者在相同的姿势下表现出非常不同的 PD 模式。基于这些结果，我们详细分析了在 STI 中如何确定 PD 上的优势手。
