This book brings new ideas to bear on an old problem. The old problem is that of self-knowledge and the self; the new ideas are based on analyses of ecological and social perception. James J. Gibson (1979) was the first theorist to insist that perceiving the self is an inevitable counterpart of perceiving the environment. Gibson's ideas are basic to the notion of an ecological self, which will be elaborated in this chapter. But the view of perception to be presented here is not simply ecological; it is social as well. Face-to-face interaction between individuals establishes a sense of an interpersonal self that is very different from anything the inanimate environment can offer. Both forms of self-perception appear very early in life, and both give rise to the experience of effective agency that is such an important component of self-awareness. They are the foundation on which other, more intellectual aspects of the self are built.

Because the term self has more than one meaning, it is best to begin with definitions. Distinctions among various kinds of self have been proposed for more than a century: William James's (1890) contrast between the “I” and the “me” was only the first of many such contrasts.

Experimental background

The first experimental test of self-recognition in animals was conducted on a group of preadolescent chimpanzees and several species of monkeys (Gallup, 1970). Initially all of the animals acted as if they were seeing other animals when they looked at themselves in the mirror. After a couple of days, however, the chimpanzees (but not the monkeys) began to respond as if they had come to appreciate the dualism implicit in mirrors and now realized that their behavior was the source of the behavior being depicted in the reflection. That is, rather than responding to the mirror as such with species-typical patterns of social behavior, they began to show self-directed responding by using the mirror to respond to themselves (e.g., to investigate parts of their bodies that they had not seen before). In an attempt to validate my impressions of what had transpired, I devised a more rigorous, unobtrusive test of selfrecognition. After the 10th day of mirror exposure the chimpanzees were placed under anesthesia and removed from their cage. While the animals were unconscious, I applied a bright red, odorless, alcohol-soluble dye (rhodamine-B base) to the uppermost portion of an eyebrow ridge and the top half of the opposite ear. The subjects were then returned to their cages in the absence of the mirror and allowed to recover from anesthetization.

Bonobos are the only species of great ape for which there are no data concerning self-recognition. Although there is little evidence reported for self-recognition in New or Old World monkeys (see Anderson, 1984; Boccia, SAAH23; Thompson & Boatright-Horowitz, SAAH22), mirror image stimulation (MIS) has been established to elicit behaviors indicative of visual selfrecognition in humans, chimpanzees, orangutans, and gorillas (see Gallup, 1987; Lewis & Brooks-Gunn, 1979, for reviews; Miles, SAAH16; Patterson & Cohn, SAAH17). In an effort to determine to what extent, if any, visual selfrecognition exists in bonobos, a study was conducted at the Yerkes Regional Primate Research Center main station and at the Yerkes field station.

Bonobos have until recently been classified as pygmy chimpanzees, but closer examination has revealed significant differences between what are now recognized as two distinct species of the genus Pan (see reviews by Susman, 1984; de Waal, 1991). Bonobos are physically smaller, walk bipedally more often (Doran, 1992), and exist in larger and more sexually active social groups than do “common” chimpanzees (Kano, 1982). Bonobos also exist in smaller ranges and total numbers in the wild than do chimpanzees, and so their exposure to and interaction with humans has been limited. Less than fifty bonobos are currently in captivity in the United States. The language-trained bonobos Matata and her son Kanzi (see Savage-Rumbaugh, 1986) have been observed by the authors to engage in mirror-aided grooming of their teeth and heads; yet until now, no controlled studies have been conducted on selfawareness in bonobos.

Abstract: The posterior parietal cortex (PPC) is the most likely site where egocentric spatial relationships are represented in the brain. PPC cells receive visual, auditory, somaesthetic, and vestibular sensory inputs; oculomotor, head, limb, and body motor signals; and strong motivational projections from the limbic system. Their discharge increases not only when an animal moves towards a sensory target, but also when it directs its attention to it. PPC lesions have the opposite effect: sensory inattention and neglect. The PPC does not seem to contain a “map” of the location of objects in space but a distributed neural network for transforming one set of sensory vectors into other sensory reference frames or into various motor coordinate systems. Which set of transformation rules is used probably depends on attention, which selectively enhances the synapses needed for making a particular sensory comparison or aiming a particular movement.

The aim of this chapter is to develop the idea that an important part of human action is driven by internal rather than external factors. The basic postulates are that internally driven actions result from autonomous processes, that they are based on representations that anticipate the effects of interaction of the self with the external milieu, and finally, that they play an important role in structuring the self. The first part of the chapter presents a brief historical account of the notions of intention and representation as envisioned in the context of the generation and control of actions. A second part is devoted to exploring the field of mental imagery, which represents a new approach to representational phenomena. Finally, the third part deals with the nature of representational systems that may account for producing voluntary action.

The neurophysiological correlates of intention

What are the respective roles of stimulus-driven and representation-driven actions in structuring our knowledge about the external world? The issue is at the core of a long-lasting debate between two schools of thought. I will call centralist the school that holds that experience and knowledge grow from actions that are the expression of a mental content.

“The stage is set, enter the hero of the play… We take a new step, long deferred and often anticipated, and introduce the Ego” (Koffka, 1935, p. 319). So begins the second half of a book that played an important role in my early education as a psychologist. This was Kurt Koffka's way of introducing his treatment of action. The ego he considered a field object, segregated from other objects, and also the “executive” in control of behavior.

There are many other ways of discussing the ego (see Neisser, 1988). I am going to refer to the “self,” as Neisser did, rather than the ego, because the term carries less literary and moral baggage. My aim is to show the way in which the self is rooted in perception. “You” are an object in a world of other objects, and I perceive you as such. So, indeed, am “I,” and just as surely I perceive myself as an object in the same world of things and events that I locate you in.

Introduction

Several studies of how chimpanzees (Pan troglodytes) and orangutans (Pongo pygmaeus) respond to their reflections in a mirror have established that these primates share with humans the capacity for self-recognition (Gallup, 1970; Lethmate & Dücker, 1973; Miles, SAAH16; Suarez & Gallup, 1981). Recent data on gorillas (Gorilla gorilla) (Patterson & Cohn, SAAH17; Swartz & Evans, SAAH11) strongly suggest that these great apes also are capable of self-recognition. Although the relationship between mirror self-recognition (MSR) and self-awareness in the sense used by social psychologists remains to be clarified (see Mitchell, SAAH6), there is general agreement that selfrecognition implies the existence of some kind of cognitive (as opposed to a merely kinesthetic) self-awareness. This may in turn allow for the expression of a range of behaviors reflecting a “theory of mind” (Crook, 1988; Gallup, 1982; Humphrey, 1984; Whiten, 1991), although the relationship between self-recognition and theory of mind (ToM) remains to be clarified, as certain subjects (e.g., autistic children, Baron-Cohen, 1992) may show the former but not the latter (Gergely, SAAH5; Mitchell, 1993).

In contrast to the numerous demonstrations of self-recognition in great apes, studies of reactions to mirror-image stimulation (MIS) in monkeys have consistently failed to find evidence of self-recognition (reviews: Anderson, 1984a; Gallup, 1987). It has been suggested that the contrasting performances between great apes and monkeys on tests of self-recognition reflect the existence of a fundamental difference in cognition – concerning self-awareness – between the self-recognizing Pongidae and other nonhuman primates (Gallup, 1982, 1987).

Abstract: The hypothesis that the central nervous system (CNS) generates movement as a shift of the limb's equilibrium posture has been corroborated experimentally in studies involving single- and multijoint motions. Posture may be controlled through the choice of muscle length-tension curve that set agonist-antagonist torque-angle curves determining an equilibrium position for the limb and the stiffness about the joints. Arm trajectories seem to be generated through a control signal defining a series of equilibrium postures. The equilibrium-point hypothesis drastically simplifies the requisite computations for multijoint movements and mechanical interactions with complex dynamic objects in the environment. Because the neuromuscular system is springlike, the instantaneous difference between the arm's actual position and the equilibrium position specified by the neural activity can generate the requisite torques, avoiding the complex “inverse dynamic” problem of computing the torques at the joints. The hypothesis provides a simple, unified description of posture and movement as well as contact control task performance, in which the limb must exert force stably and do work on objects in the environment. The latter is a surprisingly difficult problem, as robotic experience has shown. The prior evidence for the hypothesis came mainly from psychophysical and behavioral experiments. Our recent work has shown that microstimulation of the frog spinal cord's premotoneural network produces leg movements to various positions in the frog's motor space. The hypothesis can now be investigated in the neurophysiological machinery of the spinal cord.

Abstract: Prevailing engineering-inspired theories of motor control based on sequential/algorithmic or motor-programming models are difficult to reconcile with what is known about the anatomy and physiology of the motor areas. This is partly because of certain problems with the theories themselves and partly because of features of the cortical and basal ganglionic motor circuits that seem illsuited for most engineering analyses of motor control. Recent developments in computational neuroscience offer more realistic, that is, connectionist, models of motor processing. The distributed, highly parallel, and nonalgorithmic processes in these models are inherently self-organizing and hence more plausible biologically than their more traditional algorithmic or motor-programming counterparts. The newer models also have the potential to explain some of the unique features of natural, brain-based motor behavior and to avoid some of the computational dilemmas associated with engineering approaches.

Abstract: To investigate neural mechanisms of movement, physiologists have analyzed the activity of task-related neurons in behaving animals. The relative onset latencies of neural activity have been scrutinized for evidence of a functional hierarchy of sequentially recruited centers, but experiments reveal that activity changes occur largely in parallel. Neurons whose activity covaries with movement parameters have been sought for evidence of explicit coding of parameters such as active force, limb displacement, and behavioral set. Neurons with recognizable relations to the task are typically selected from a larger population, ignoring those cells with complex relations to the task and unmodulated cells. Selective interpretations are also used to support the notion that different motor regions perform different motor functions; again, current evidence suggests that units with similar properties are distributed over widely different regions.

These coding issues are reexamined for premotoneuronal (PreM) cells, whose correlational links with motoneurons are revealed by spike-triggered averages. PreM cells are recruited over long times relative to their target muscles; they show diverse response patterns relative to the muscle force they produce; functionally disparate PreM cells such as afferent fibers and descending corticomotoneuronal and rubromotoneuronal cells can exhibit similar patterns. Neural mechanisms have been further elucidated by neural network simulations of sensorimotor behavior; the pre-output hidden units typically show diverse response patterns in relation to their target units.

This fifth Emory Symposium in Cognition is both like and unlike its predecessors. It resembles them in its recognizably ecological emphasis, as well as in its attempt to integrate the study of adult cognition with that of development. Unlike them, however, its scope is not defined by a traditional field like “memory” or “categorization.” Instead, it is delineated by a more fundamental distinction, that between the self and everything else. William James said it best: “Each of us dichotomizes the Kosmos at a different place” (1890: 290). As perceivers and thinkers, all human beings learn things about both sides of that dichotomy. We perceive, remember, and think about the world around us, but also about ourselves. This book, the first of three projected volumes, deals with perceiving. It focuses on two forms of self perception, the ecological and the interpersonal A companion volume on the remembering self follows soon; a third, still in preparation, will focus on self-concepts.

The self may be a new topic for cognitive psychologists, but not for everyone. Philosophers and psychologists of various persuasions have written about it for many years with considerable insight.

Abstract: This target article draws together two groups of experimental studies on the control of human movement through peripheral feedback and centrally generated signals of motor commands. First, during natural movement, feedback from muscle, joint, and cutaneous afferents changes; in human subjects these changes have reflex and kinesthetic consequences. Recent psychophysical and microneurographic evidence suggests that joint and even cutaneous afferents may have a proprioceptive role. Second, the role of centrally generated motor commands in the control of normal movements and movements following acute and chronic deafferentation is reviewed. There is increasing evidence that subjects can perceive their motor commands under various conditions, but that this is inadequate for normal movement; deficits in motor performance arise when the reliance on proprioceptive feedback is abolished either experimentally or because of pathology. During natural movement, the CNS appears to have access to functionally useful input from a range of peripheral receptors as well as from internally generated command signals. The unanswered questions that remain suggest a number of avenues for further research.