In The Roots of Thinking (1990), Sheets-Johnstone argues that several concepts fundamental to human thought first originated from bodily experience in pre-humans. Relatively few cognitive or neurobiological findings appear in the primarily philosophical and anthropological text. As the book discusses several intriguing ideas for which disappointingly few laboratory findings pertain, this review advocates experimental research on three such topics.
2. After bracketing, the next methodological step ("corporeal scanning") involves noticing correspondence between experientially accessible attributes (e.g., felt hardness and utility for food processing) which are available in both the body (teeth) and beyond the body (stone). Given a particular concept, bodily experience is scanned to determine whether one or more aspects of the lived body match the target concept. "The concept of hardness, for instance, is latent in the tactile-kinesthetic act of brushing the tongue across the teeth (p. 18)." Sheets-Johnstone argues that it is the experienced sensory attributes which provided the semantic foundation for the origin of several novel concepts (e.g., flaked-edge stone tools) based on intrinsically familiar bodily experiences (with teeth). After deducing somatic origins of several concepts via corporeal analysis, Sheets- Johnstone concludes that "the body... is not simply implicated in meanings through its very acts but is the very source or standard upon which those meanings are forged in the first place (p. 361)."
3. Corporeal analysis is brought to life through numerous experiential descriptions, but the reader is warned not to rely too heavily on language: "The analyses describe corporeal experience -- they are phenomenological, which means that they are empirically verifiable by the reader.. Taking time to have the experience is thus clearly a first step the reader must take... Thus the analyses... can be validated only on their own ground -- by readers who allow their bodies to be heard (p. 19)." This combined warning and invitation might be more accessible to some readers than others. We should remember that previous debate on the existence of "mental imagery" (i.e., visual imagery) hinged in part on individual differences in phenomenology amongst the debating scientists and philosophers. If we are not careful, a similar, uneven distribution of somesthetic attentional skills might initially confuse our collective thought regarding bodily perception tasks such as corporeal scanning. Perhaps, as with visual imagery, the most convincing arguments will be based on experimental findings. Regardless of the status accorded to the phenomenological method of corporeal analysis, in Sheets-Johnstone's hands it has revealed at least three topics which should be investigated in a full-bodied experimental psychology.
4. Before discussing particular topics deserving greater study, here are a few comments for potential readers of the book. The book conists of several self-encapsulated chapters. To a nonphilosopher, the terminology appears abstruse at first glance, but explicit definitions are usually provided. Redundant elucidation of key concepts throughout the book facilitates the understanding of single chapters read in isolation. The thoughtful narrative offers highly skilled word-crafting, convincing descriptions fueled by keen observation, and plenty of logical argument. Sometimes complicated, the arguments are clearly laid out and cover important ground.
5. Bodily perception, sense modalities, and space perception are three psychological issues discussed in this book which offer clear opportunities for experimental investigation. Bodily perception, which forms the backbone of Sheets-Johnstone's methodology, constitutes one of the largest sparsely studied topics in psychology. This scientific neglect stems in part from inherent difficulty in controlling somatic stimuli for experimentation, though modern innovations in psychophysiological measurement and experimental design might now contribute to more rapid progress in this area. Bodily perception is distinguished by several intriguing aspects. For example, the external and the internal environments can be confounded in initial stages of somatosensory input. That is, some of the receptors in skin, tendons, and joints which provide haptic information (concerning attributes of touched or held objects) may also contribute to somesthesis (e.g., perception of tissue states). Yet somehow this mixture at the input stage does not usually lead to confused perception of external and internal stimuli. Though haptic cognition already constitutes a nascent area of research (Lederman & Klatzky, 1987) , the possible topic of "somesthetic cognition", concerning mental processes related to the body as such, still awaits investigation.
6. The nature of body as physical self poses difficult questions for bodily perception. Consider the experience of bodily states which occur in cases of influenza, broken bones, or amputation. To the extent that perceived bodily states compel shifts in self-image, might somesthetic perception uniquely contribute to self-perception? What psychological mechanisms mediate relations between self-awareness, self-concept, and somesthetic perception? Moreover, perception of the internal environment must have unique relations with the myriad neural control systems which regulate bodily organs. For example, the constant opportunity for feedback regulation within the body suggests peculiar links between imagery and perception whereby imagined warmth or relaxation can lead to physical changes in blood circulation or muscle tension. These physical changes can lead to changes in perceived temperature or muscle stiffness. Such covert control of tissue states which modulate somesthetic stimuli reveals a profound difference from exteroceptive sense modalities: imagining the color green does not produce green stimuli in the world.
7. Comparable to the enigmas of bodily perception, psychological relations between sense modalities are also poorly understood. For example, Sheets-Johnstone attributes pervasive bias for vision superseding somatosensation to cultural factors, but some of this visual dominance might stem from neurobiological constraints. Modality bias is not the only unsolved problem in this area which concerns bodily perception. Psychologists and other scientists have not yet agreed on a classification of sense modalities. As there is no single definition which distinguishes each sense modality from the others, lists of sense modalities vary in number from five to many more than five. All the non-unanimously designated modalities pertain to somesthesis (Geldard, 1948), revealing the corporeal locus of this dispute.
8. Though sense modalities are usually studied "in isolation", it seems likely that intermodal relations are central to several core areas of cognitive psychology. For example, abundant correspondences among sensory dimensions from different sense modalities (such as high vs. low auditory pitch and visual vertical location) may provide a framework for semantic structure (see Marks, 1978). Moreover, many objects may be recognized even when using only one of several possible sense modalities, so some correspondence among modalities may be linked to physical object properties. For example, surface roughness can be seen or felt with the skin, and this coherence between visible and tangible aspects of texture seems to constrain the psychological representation of fingertip vibrations (Grossenbacher, 1993). Further investigation of relations between sense modalities requires expertise spanning more than one classically defined psychological area, so we should encourage collaboration among like-minded but differently trained investigators.
9. The third topic which requires greater scrutiny has already attracted sustained investigation by many psychologists and neurobiologists, though with relatively little emphasis on the body. Space perception operates through multiple sense modalities and entails representations having a variety of spatial frameworks, with different boundaries, metrics, and dimensions. Some dimensions, such as left-right laterality, appear to span several modalities (Stein & Meredith, 1993). For Sheets-Johnstone, the concepts of left and right arise from human bodily experience (p. 289), and upright posture constrains behavior and experience in other important ways (p. 336). For example, spatial relations between head-centered and torso-centered frameworks hinge on the distinction between quadrupedal and bipedal stance. Moreover, control of binary gait and manual activities may require unique spatial representations for navigation and object manipulation. These representations can be studied experimentally. For example, selective attention to one hand can be more efficient when the other hand, which receives simultaneous distracting stimulation, is positioned far from, rather than near to, the attended hand (Driver & Grossenbacher, in press). This recent finding underscores the importance of proprioceptive contributions (specifying limb positions) to spatial representations in which attention operates.
10. In summary, The Roots of Thinking offers an instructive application of somatic phenomenology to the problem of conceptual origins. But perhaps the current psychological understanding of bodily perception too closely resembles knowledge of visual perception during the Gestalt era. Several of the psychological issues encountered in this book appear strikingly accessible to experimental study without reliance on introspection. Fortunately, there are two areas of research involving cognition and the body which have blossomed in the last decade. Indeed, recent developments in haptic perception and motor control might spur new advances in the psychological study of sensory and non-motoric control functions of the body. Of course, technical difficulty (e.g., stimulus control) still offers a compelling reason why advances in the study of somesthetic perception may be difficult to achieve. But now the gauntlet has been thrown, and it will be our loss if we do not attempt to meet Sheets-Johnstone's challenge. The body offers great opportunity as a multi-faceted subject for psychological inquiry. "Clearly there is a vast field of corporeal understandings awaiting discovery and cultivation by many people (p. 19)."
Driver, J. & Grossenbacher, P.G. (in press) Multimodal spatial constraints on tactile selective attention. Attention and Performance, XVI.
Geldard, F.A. (1948) Somesthesis. in E.G. Boring, H.S. Langfeld & H.P. Weld (Eds.) Foundations of Psychology. New York: John Wiley.
Grossenbacher, P.G. (1993) Interaction between touch and vision: Correspondence between frequency dimensions (Doctoral Dissertation, University of Oregon, 1992). Dissertation Abstracts International, 54, 526B.
Lederman, S.J. & Klatzky, R.L. (1987). Hand movements: A window into haptic object recognition. Cognitive Psychology, 19, 342-368.
Marks, L.E. (1978) The unity of the senses: Interrelations among the modalities. New York: Academic Press.
Sheets-Johnstone, M. (1990) The Roots of Thinking. Philadelphia: Temple University Press.
Sheets-Johnstone, M. (1994) Precis of: The Roots of Thinking. PSYCOLOQUY 5(8) evolution-thinking.1.sheets-johnstone.
Stein, B.E. & Meredith, M.A. (1993) The merging of the senses. Cambridge, MA: MIT Press.