How well do you know the back of your hand?

Image: Solipsist (Wikipedia)

Of all the many and varied objects we encounter in the world, we would ordinarily presume that we know none better than our own body. Descartes describes his pre-theoretical view of himself and his state of knowledge in Meditation 2: “As regarded the body, I did not even doubt of its nature, but thought I distinctly knew it”. However, new research reported on the BBC suggests that we do not accurately represent that most familiar of objects half as accurately as we might think. In fact, the evidence suggest that our conception of our own body is systematically misleading.

Neuroscientists at University College London set up an experiment as follows. Subjects would place a hand flat on a table. The experimenter would then cover the hand with a board, and ask the volunteer to indicate where they thought certain key points of their hand – fingertips, knuckles and joints – were located. These points allow the scientists to plot a ‘represented’ model (or “brains image”) of the subjects hand, which could then be compared with the real appendage.

The results were striking: subjects systematically represented their hands to be considerably wider than they really were: many increased the width by 80%. Likewise, the length of fingers were dramatically under-estimated, by a factor in some cases as great as 30-40%. In general, the trend is towards representing hands as broader and ‘stumpier’ than the they in fact are.

The research (available here) is focussed purely on that one specific part of the body; however, the researchers anticipate that similar findings would extend to body image and perception more generally. Lead researcher Dr Matthew Longo expects that the study’s findings could provide an explanatory basis for certain psychiatric conditions, such as anorexia.

Hence we have still greater reason to doubt Descartes’ proclamation. It seems that our bodies are a good deal less familiar to ourselves than they might seem.

Related Article:

Self-Knowledge: Rationalism vs. Empiricism
By Aaron Z. Zimmerman
University of California, Santa Barbara
(Vol.3, January 2008)
Philosophy Compass

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