The use of realistic and mechanical hands in the rubber hand illusion,and the relationship to hemispheric differences

Embodiment, as measured through the rubber-hand illusion (RHI), depends on the similarity between object to be embodied and part of the body it replaces. We compared a fake hand similar to a real hand, and one matched in size but made of wires (mechanical). Left and right versions were tested to investigate whether the effect of appearance was stronger in the left hand. We found that the mechanical hand induced embodiment, though to a reduced degree relative to the realistic hand (N = 120). Left and right versions of the mechanical hand did not differ in strength of the illusion. However, with the left realistic hand there was a stronger relationship between drift (an objective measure of the illusion) and agreement on the questionnaire (subjective experience). With the mechanical hand, objective and subjective measures were unrelated. We discuss the results in relation to factors that influence the RHI and hemispheric differences.     

Inverse effectiveness, multisensory integration, and the bodily self: Some statistical considerations

A recent report in Consciousness and Cognition provided evidence from a study of the rubber hand illusion (RHI) that supports the multisensory principle of inverse effectiveness (PoIE). I describe two methods of assessing the principle of inverse effectiveness (‘a priori’ and ‘post-hoc’), and discuss how the post-hoc method is affected by the statistical artefact of ‘regression towards the mean’. I identify several cases where this artefact may have affected particular conclusions about the PoIE, and relate these to the historical origins of ‘regression towards the mean’. Although the conclusions of the recent report may not have been grossly affected, some of the inferential statistics were almost certainly biased by the methods used. I conclude that, unless such artefacts are fully dealt with in the future, and unless the statistical methods for assessing the PoIE evolve, strong evidence in support of the PoIE will remain lacking.     

When I saw me standing there: first-person and third-person memories and future projections,and how they relate to the self

We studied visual perspective of three autobiographical memories and three projected future events (i.e. whether the events were experienced from a first-person or third-person perspective, or in between) in 117 undergraduate students. Perspective proved to be a reliable individual-differences variable. The majority of narratives trended toward the first-person perspective, with memories more likely to yield first-person perspective than future events. Perspective was predicted by detail (higher level of participant-reported visual detail was more likely to elicit first-person perspective), and temporal distance (events reported as being further away in time were more likely to elicit third-person perspective). Detail, in turn, was explained (among others) by the individual-differences variable of depression/social uncertainty (a factor-derived scale consisting of rumination scales, the inverse of the Sense Of Self Scale, the Social Phobia Scale, and, to a lesser extent, the Social Interaction Anxiety Scale). Generally, predictors for memories and future events overlapped. The results underscore the need for including individual-differences variables in research on the determinants of memory perspective.