Haptic perception after a change in hand size

doi:10.1016/j.neuropsychologia.2010.01.006

Neuropsychologia

Volume 48, Issue 6, May 2010, Pages 1853-1856

https://doi.org/10.1016/j.neuropsychologia.2010.01.006 Get rights and content

Abstract

When we actively explore with our hands (haptics), the brain must combine diverse sensory signals into a unified percept. Presumably, a key role is played by an internal model of the body, but the processes responsible for forming and maintaining such a model are poorly understood. We used a multisensory illusion to alter the internal model of one's hand by using fake hands smaller or larger than the participant's hand. After such brief illusion we observed a change in haptically perceived object size. These results demonstrate that the brain rapidly recalibrates haptic signals using an internal model of the hand and that this model is multisensory rather than merely visual or memory-based.

Section snippets

Participants

Fifty-six members of the University of Liverpool student population took part in the study (mean age 21 years). Half were assigned to the synchronous condition and half to the a synchronous condition. They were unaware of the hypothesis under investigation.

Materials

We cast two pairs of hands from alginate molds of real hands (Fig. 1), selected to be approximately at the 5th and 95th percentiles of male and female hand sizes, respectively. Therefore, they were within the range of anatomically plausible

Participant hand sizes

As a measure of hand size we used the linear extent between the base of the palm and the tip of the middle finger. The hand replicas for the female group were 142 and 185 cm, whereas those for the male group were 165 and 205 cm. The distribution of the hand sizes in the two participant groups are summarized by the boxplots in Fig. 1. All participant hands were indeed within the range of small and large hand replicas. Because there were individual differences in hand size, we expect differences in

Conclusion

In our experiment, participants were exposed to multisensory stimulation that led them to report (in a questionnaire) that an enlarged or reduced hand replica had become their own hand (the fake-hand illusion, Botvinick & Cohen, 1998). Immediately after stimulation, they judged an actively felt object to be larger (after exposure to the enlarged hand) or smaller (after exposure to the reduced hand) than a standard object of identical size felt by the other hand. Therefore, a short exposure to

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Therefore, tasks that compare the body with external stimuli may also dissociate from and develop differently than what is recorded using proprioceptive drift measures. Indeed, another study that implemented the RHI over different hand sizes in adults and found similar recalibration of the hand for both large and small fake hands also used a task comparing the body with external stimuli (Bruno & Bertamini, 2010). In that study, participants needed to estimate the diameter of a disk relative to a reference disk using only haptics, which was found to be modulated by induction of the RHI over a small hand and a large hand.
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If I were a grown-up: Children's response to the rubber hand illusion with different hand sizes
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These findings corroborate the plasticity of bodily self-consciousness across development; however, a more in-depth investigation of the interplay between changes (or stability) in body size representation and related perception of external objects in children could provide a better understanding of the relationship between body size representation and bodily self-consciousness. A similar approach has already been applied in research with adults by asking participants to complete perceptual tasks following the RHI (Bruno & Bertamini, 2010; Haggard & Jundi, 2009; Kilteni, Normand, Sanchez-Vives, & Slater, 2012; Pavani & Zampini, 2007) or its full body equivalent (full body illusion; Banakou et al., 2013; Normand et al., 2011; Tajadura-Jiménez et al., 2017; van der Hoort et al., 2011). Bruno and Bertamini (2010) found that, after exposure to the RHI using an enlarged or smaller fake hand (with respect to the size of participants’ own hand), participants reported objects to be larger or smaller, respectively.
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However, if the hand is also experienced as much smaller than the forearm, then an object placed on the hand must be relatively smaller than an object placed on the forearm. Indeed, the tactile size perception of objects increases when the rubber hand illusion is used to make individuals feel as if their hand is larger (Bruno & Bertamini, 2010) or when a part of the body is visually magnified (Taylor-Clarke et al., 2004). In support of reverse distortion, when comparing a body part to a non-corporal object, these distortions become severely reduced in magnitude (Linkenauger et al., 2015).
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Brief communicationHaptic perception after a change in hand size

Abstract

Section snippets

Participants

Materials

Participant hand sizes

Conclusion

Current Biology

Consciousness and Cognition

Behavioural Brain Research

Cortex

An integrated system for dextrous manipulation

Proceedings of the IEEE International Conference on Robotics and Automation

Representation of object size in the somatosensory system

Journal of Neurophysiology

Rubber hands ‘feel’ touch that eyes see

Nature

Observations on active touch

Psychological Review

Brief communication
Haptic perception after a change in hand size