Slater Mel, Ehrsson H Henrik
Event Lab, Department of Clinical Psychology and Psychobiology, University of Barcelona, Barcelona, Spain.
Institute of Neurosciences of the University of Barcelona, Barcelona, Spain.
Front Hum Neurosci. 2022 Jun 16;16:834492. doi: 10.3389/fnhum.2022.834492. eCollection 2022.
Some recent papers by P. Lush and colleagues have argued that the rubber hand illusion (RHI), where participants can feel a rubber hand as their own under appropriate multisensory stimulation, may be caused mainly by hypnotic suggestibility and expectations (demand characteristics). These papers rely primarily on a study with 353 participants who took part in a RHI experiment carried out in a classical way with brush stroking. Participants experienced a synchronous condition where the rubber hand was seen to be touched in synchrony with touch felt on their corresponding hidden real hand, or the touches were applied asynchronously as a control. Each participant had a related measure of their hypnotisability on a scale known as the Sussex-Waterloo Scale of Hypnotisability (SWASH). The authors found a correlation between the questionnaire ratings of the RHI in the synchronous condition and the SWASH score. From this, they concluded that the RHI is largely driven by suggestibility and further proposed that suggestibility and expectations may even entirely explain the RHI. Here we examine their claims in a series of extensive new analyses of their data. We find that at every level of SWASH, the synchronous stimulation results in greater levels of the illusion than the asynchronous condition; moreover, proprioceptive drift is greater in the synchronous case at every level of SWASH. Thus, while the level of hypnotisability does modestly influence the subjective reports (higher SWASH is associated with somewhat higher illusion ratings), the major difference between the synchronous and asynchronous stimulation is always present. Furthermore, by including in the model the participants' expectancy ratings of how strongly they initially believed they would experience the RHI in the two conditions, we show that expectations had a very small effect on the illusion ratings; model comparisons further demonstrate that the multisensory condition is two-to-three-times as dominant as the other factors, with hypnotisability contributing modestly and expectations negligibly. Thus, although the results indicate that trait suggestibility may modulate the RHI, presumably through intersubject variations in top-down factors, the findings also suggest that the primary explanation for the RHI is as a multisensory bodily illusion.
P. 勒什及其同事近期发表的一些论文认为，在适当的多感官刺激下，参与者会将橡胶手当作自己的手来感受的橡皮手错觉（RHI），可能主要是由催眠易感性和期望（需求特征）引起的。这些论文主要依据一项针对353名参与者的研究，这些参与者参加了一项以经典方式用刷子轻抚进行的橡皮手错觉实验。参与者经历了同步条件，即看到橡胶手与他们相应隐藏的真实手部所感受到的触摸同步被触摸，或者触摸以异步方式施加作为对照。每个参与者都有一个在名为苏塞克斯 - 滑铁卢催眠易感性量表（SWASH）上的相关催眠易感性测量值。作者发现同步条件下橡皮手错觉的问卷评分与SWASH分数之间存在相关性。据此，他们得出结论，橡皮手错觉在很大程度上是由易受暗示性驱动的，并进一步提出易受暗示性和期望甚至可能完全解释橡皮手错觉。在此，我们通过对他们的数据进行一系列广泛的新分析来检验他们的说法。我们发现，在SWASH的每个水平上，同步刺激产生的错觉水平都高于异步条件；此外，在SWASH的每个水平上，同步情况下本体感觉漂移都更大。因此，虽然催眠易感性水平确实会适度影响主观报告（较高的SWASH与略高的错觉评分相关），但同步和异步刺激之间的主要差异始终存在。此外，通过在模型中纳入参与者对他们最初认为在两种条件下体验橡皮手错觉的强烈程度的期望评分，我们表明期望对错觉评分的影响非常小；模型比较进一步证明，多感官条件的主导作用是其他因素的两到三倍，催眠易感性的贡献适度，期望的贡献可忽略不计。因此，尽管结果表明特质易受暗示性可能会调节橡皮手错觉，大概是通过自上而下因素的个体间差异，但研究结果也表明，橡皮手错觉的主要解释是一种多感官身体错觉。
