| Summary: | Thesis (Ph.D.)--Memorial University of Newfoundland, 1978. Psychology Bibliography : leaves 231-239 This paper is composed of two parts, the first being a theoretical account of the topic at hand, the knowledge of limb-length, and the second being a description of a series of experiments designed to demonstrate that knowledge of limb-length constitutes a newly-discovered adaptive mechanism. -- In Part I, it is suggested that in order to carry out a wide variety of kinesthetic and motor functions, the brain must have a knowledge of the lengths of all of the body segments, including the length of the limbs, which is of particular present concern. However, a search of the relevant literature in human experimental psychology, medicine, and general biological science has revealed that this is a topic which has, by and large, been completely overlooked and unexplored prior to the present investigation. Therefore, argument by example, by logical necessity, and by inference from a few medical and psychological phenomena (e.g. phantom limb), is given in support of the contention that knowledge of limb-length is a real, existing cerebral mechanism and that it constitutes an integral, essential, and prerequisite part of human kinesthetic and motor function. -- Since such a system has never been considered before, a brief theoretical proposal is given concerning the underlying basis of such a mechanism with respect to other known kinesthetic and proprioceptive systems. It is proposed that knowledge of limb-length — termed 'registered limb-length1— along with knowledge of body volume, constitutes one part of a larger and superordinate system of body knowledge, termed the 'proprioceptive knowledge system'. The other sub-systems involved in this latter system are the joint-angle knowledge system and the system involving knowledge of cutaneous stimulation. It is further argued that all three sub-systems are cross-calibrated and that each is also calibrated against other spatial systems, particularly vision. Finally, it is suggested that registered limb-length might also be capable of recalibration in response to adaptive requirements. -- In Part II, brief consideration is given to a set of experiments on perceptual adaptation to displacing prisms which led to the present proposal concerning knowledge of limb-length. This is followed by a description of six experiments which attempt to demonstrate that registered limb-length can be recalibrated in response to imposed perceptual discrepancies. It is concluded from analyses of subject performance in reaching tasks following exposure to both displacing prisms and kinesthetic discrepancies, that a system involving registered limb-length does exist and that it is, in fact, capable of recalibrated change under certain circumstances. Some implications of this discovery are discussed.
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