The experience of body boundaries by Siamese twins

Siamese twins share some body surface, and may also share organs and/or lim bs, as well as having areas of joint sensation and movement. Apart from iss ues relating to the nature-nurture debate, psychology has paid little atten tion to the phenomena of Siamese twinning. This paper discusses the phenome nal experience of body boundaries by Siamese twins in relation to issues of self and identity. It is argued that aspects of individual embodiment prov ide an ambiguous body boundary for this group. Specifically, it is argued t hat phenomena such as areas of common tactile sensation (overlapping 'senso ry rims') and the ability to move shared limbs (divided 'authorship of acti on'), fosters an experience of body as sentiently and spatially extended in to their sibling. (C) 2001 Elsevier Science Ltd. All rights reserved.