Universiteit Leiden

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Dissertation

Is this really my hand?

A virtual hand that feels as if it is your own. Feeling happier because a virtual face is smiling with you. Cognitive Psychologist Ke Ma discovered using virtual reality that the way we experience our body is more flexible than we thought. Ma: ‘We can think up some fantastic applications.' PhD defence 18 February.

Author
Ke Ma
Date
22 July 2016
Links
Investigating self-representation with virtual reality

Body ownership

We have no difficulty at all distinguishing our own body from that of other people. Our experience of 'body ownership' tells us that this is our body. PhD candidate Ma has discovered that people can easily integrate objects into their body ownership. It is the feeling of controlling a virtual body part  that gives us the idea that that virtual body part is actually ours. If a virtual person laughs at the same time as a real person, that can even influence our mood.  

Virtual reality

In his PhD research Ke Ma used virtual reality to project images of a virtual hand and a virtual face. He then conducted a number of studies with between 20 and 60 test subjects. In these tests the participants could move a virtual hand - and even a virtual face - themselves. Ma: ‘This experiment showed us that having control is what largely determines whether you feel that your body - or a particular body part - is yours.’

Virtual hand

This experience of body ownership seems to be very flexible and can extend to 'foreign' body parts. Traditional studies generally use the 'rubber hand illusion', but a problem with this method is that the test subject cannot move the hand himself or herself. This makes the illusion rather limited because in real life people can move their hand; it's something we do to determine whether it is actually our hand. Compared to the rubber hand illusion, the virtual hand illusion gives you the feeling of being able to control the hand, which reinforces the feeling that the limb belongs to you. Ma's findings go even further: 'We have also shown with the virtual face illusion that we can influence mood and behaviour. If the virtual face smiles and you then control the movement of the virtual face by moving your own head, this increases your feeling of happiness.' This applies even if you can only move the face, but without affecting the facial expression.

Fantastic applications 

PhD candidate Ma wanted to know more about the experience of body ownership and whether this is a flexible concept. 'Now we have some clearer ideas about it, we can think of some fantastic applications. We can, for example, let people think that they have foreign body parts.' Are there medical applications that can come out of this research? Ma: ‘We have already done research with healthy test subjects, so I would say it definitely has potential. It is difficult, though, because you have to combine a lot of expertise and technical skill.'

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