In this updated and extended edition of their book, Goodale and Milner explore one of the most extraordinary neurological cases of recent years--one that profoundly changed scientific views on the visual brain. Taking us on a journey into the unconscious brain, this book is a fascinating illustration of the power of the 'unconscious' mind.

Vision, more than any other sense, dominates our mental life. Our visual experience is just so rich, so detailed, that we can hardly distinguish that experience from the world itself. Even when we just think about the world and don't look at it directly, we can't help but 'imagine' what it looks like. We think of 'seeing' as being a conscious activity--we direct our eyes, we choose what we look at, we register what we are seeing. The series of events (...) described in this book radically altered this attitude towards vision. This book describes one of the most extraordinary neurological cases of recent years--one that profoundly changed scientific views on consciousness. It is the story of Dee Fletcher--a woman recently blinded--who became the subject of a series of scientific studies. As events unfolded, Milner and Goodale found that Dee wasn't in fact blind--she just didn't know that she could see. Taking us on a journey into the unconscious brain, the two scientists who made this incredible discovery tell the amazing story of their work, and the surprising conclusion they were forced to reach. Written to be accessible to students and popular science readers, this book is a fascinating illustration of the power of the 'unconscious' mind. (shrink)

Although the mechanics of how the eye works are well understood, debate still exists as to how the complex machinery of the brain interprets neural impulses...

It is our contention that the concept of planning in Glover's model is too broadly defined, encompassing both action/goal selection and the programming of the constituent movements required to acquire the goal. We argue that this monolithic view of planning is untenable on neuropsychological, neurophysiological, and behavioural grounds. The evidence demands instead that a distinction be made between action planning and the specification of the initial kinematic parameters, with the former depending on processing in the ventral stream and the latter (...) on processing in the dorsal stream. (shrink)

O'Regan & Noë run into some difficulty in trying to reconcile their “seeing as acting” proposal with the perception and action account of the functions of the two streams of visual projections in the primate cerebral cortex. I suggest that part of the problem is their reluctance to acknowledge that the mechanisms in the ventral stream may play a more critical role in visual awareness and qualia than mechanisms in the dorsal stream.

Dijkerman & de Haan (D&dH) propose a convincing model of somatosensory organization that is inspired by earlier perception-action models of the visual system. In this commentary, we suggest that the dorsal and ventral visual streams both contribute to the control of action, but in different ways. Using the example of grip and load force calibration, we show how the ventral stream can invoke stored information about the material properties of objects originally derived from the somatosensory system.

Visual systems first evolved not to enable animals to perceive the world, but to provide distal sensory control of their movements. Conscious sight is a relatively recent invention, but its emergence has enabled organisms such as humans and other primates to carry out complex cognitive operations on a detailed perceptual representation of the world. The two streams of visual processing that have been identified in the primate cerebral cortex are a reflection of these two functions of vision. The dorsal 'action' (...) stream projecting from early visual areas to the posterior parietal cortex mediates the visual control of skilled motor acts. The ventral 'perceptual' stream projecting from early visual areas to the temporal lobe provides a perceptual experience of the world beyond our bodies. Both streams work together in the production of adaptive behavior. (shrink)

Vision is so closely identified with visual phenomenology that we sometimes forget that the visual system does more than deliver our experience of the world. Vision also plays a critical role in the control of our movements, from picking up our coffee cups to playing tennis. But the visual control of movement has, until recently, been relatively neglected. Indeed, traditional accounts of vision, while acknowledging the role of vision in motor control, have simply regarded such control as part of a (...) larger function—that of constructing an internal model of the external world. Even though such accounts might postulate separate ‘modules’ for the processing of different visual features, such as motion, colour, texture, and form, in most of these accounts there is an implicit assumption that, in the end, vision delivers a single representation of the external world—a kind of simulacrum of the real thing that serves as the perceptual foundation for all visually driven thought and action. (shrink)

Vision is so closely identified with visual phenomenology that we sometimes forget that the visual system does more than deliver our experience of the world. Vision also plays a critical role in the control of our movements, from picking up our coffee cups to playing tennis. But the visual control of movement has, until recently, been relatively neglected. Indeed, traditional accounts of vision, while acknowledging the role of vision in motor control, have simply regarded such control as part of a (...) larger function – that of constructing an internal model of the external world. Even though such accounts might postulate separate ‘modules’ for the processing of different visual features, such as motion, colour, texture, and form, in most of these accounts there is an implicit assumption that, in the end, vision delivers a single representation of the external world – a kind of simulacrum of the real thing that serves as the perceptual foundation for all visually driven thought and action. (shrink)

Hommel et al. propose that high-level perception and action planning share a common representational domain, which facilitates the control of intentional actions. On the surface, this point of view appears quite different from an alternative account that suggests that “action” and “perception” are functionally and neurologically dissociable processes. But it is difficult to reconcile these apparently different perspectives, because Hommel et al. do not clearly specify what they mean by “perception” and “action planning.” With respect to the visual control of (...) action, a distinction must be made between conscious visual perception and unconscious visuomotor processing. Hommel et al. must also distinguish between the what and how aspects of action planning, that is, planning what to do versus planning how to do it. (shrink)

The visual control of action is a critical ability for interacting with the visual environment. Visual perception, however, is necessary for recognizing and memorizing different aspects of this environment. According to an influential proposal by Goodale and Milner, these two distinct visual functions are mediated by different cortical areas. The ventral visual stream mediates perception and the dorsal stream mediates the visual control of action. In this review, we focus on behavioral evidence looking at potential differences in the principles (...) governing visual organization for perception and action. We propose that, unlike visual perception, which is largely governed by relational and Gestalt representations of objects, visually-guided action treats objects in a more analytic fashion. We review evidence from visual illusions, studies of object–shape perception, and psychophysical studies of visual resolution of size to support this idea. We conclude that the visual perception of objects and their relations tends to be holistic and contextual in nature, whereas the visual control of skilled actions is more analytical, circumscribed, and tuned to the real metrics of the visual environment. (shrink)

The McCollough effect, an orientation-contingent color aftereffect, has been known for over 30 years and, like other aftereffects, has been taken as a means of probing the brain's operations psychophysically. In this paper, we review psychophysical, neuropsychological, and neuroimaging studies of the McCollough effect. Much of the evidence suggests that the McCollough effect depends on neural mechanisms that are located early in the cortical visual pathways, probably in V1. We also review evidence showing that the aftereffect can be induced without (...) conscious perception of the induction patterns. Based on these two lines of evidence, it is argued that our conscious visual experience of the world arises in the cortical visual system beyond V1. (shrink)

Many studies have argued for distinct but complementary contributions from each hemisphere in the control of movements to visual targets. Investigators have attempted to extend observations from patients with unilateral left- and right-hemisphere damage, to those using neurologically-intact participants, by assuming that each hand has privileged access to the contralateral hemisphere. Previous attempts to illustrate right hemispheric contributions to the control of aiming have focussed on increasing the spatial demands of an aiming task, to attenuate the typical right hand advantages, (...) to try to enhance a left hand reaction time advantage in right-handed participants. These early attempts have not been successful. The present study circumnavigates some of the theoretical and methodological difficulties of some of the earlier experiments, by using three different tasks linked directly to specialized functions of the right hemisphere: bisecting, the gap effect, and visuospatial localization. None of these tasks were effective in reducing the magnitude of left hand reaction time advantages in right handers. Results are discussed in terms of alternatives to right hemispheric functional explanations of the effect, the one-dimensional nature of our target arrays, power and precision given the size of the left hand RT effect, and the utility of examining the proportions of participants who show these effects, rather than exclusive reliance on measures of central tendency and their associated null hypothesis significance tests. (shrink)

When we reach to pick up an object, our actions are effortlessly informed by the object’s spatial information, the position of our limbs, stored knowledge of the object’s material properties, and what we want to do with the object. A substantial body of evidence suggests that grasps are under the control of “automatic, unconscious” sensorimotor modules housed in the “dorsal stream” of the posterior parietal cortex. Visual online feedback has a strong effect on the hand’s in-flight grasp aperture. Previous work (...) of ours exploited this effect to show that grasps are refractory to cued expectations for visual feedback. Nonetheless, when we reach out to pretend to grasp an object (pantomime grasp), our actions are performed with greater cognitive effort and they engage structures outside of the dorsal stream, including the ventral stream. Here we ask whether our previous finding would extend to cued expectations for haptic feedback. Our method involved a mirror apparatus that allowed participants to see a “virtual” target cylinder as a reflection in the mirror at the start of all trials. On “haptic feedback” trials, participants reached behind the mirror to grasp a size-matched cylinder, spatially coincident with the virtual one. On “no-haptic feedback” trials, participants reached behind the mirror and grasped into “thin air” because no cylinder was present. To manipulate haptic expectation, we organized the haptic conditions into blocked, alternating, and randomized schedules with and without verbal cues about the availability of haptic feedback. Replicating earlier work, we found the strongest haptic effects with the blocked schedules and the weakest effects in the randomized uncued schedule. Crucially, the haptic effects in the cued randomized schedule was intermediate. An analysis of the influence of the upcoming and immediately preceding haptic feedback condition in the cued and uncued random schedules showed that cuing the upcoming haptic condition shifted the haptic influence on grip aperture from the immediately preceding trial to the upcoming trial. These findings indicate that, unlike cues to the availability of visual feedback, participants take advantage of cues to the availability of haptic feedback, flexibly engaging pantomime, and natural modes of grasping to optimize the movement. (shrink)

David Milner and Melvyn Goodale’s dissociation hypothesis is commonly taken to state that there are two functionally specialized cortical streams of visual processing originating in striate (V1) cortex: a dorsal, action-related “unconscious” stream and a ventral, perception-related “conscious” stream. As Milner and Goodale acknowledge, findings from blindsight studies suggest a more sophisticated picture that replaces the distinction between unconscious vision for action and conscious vision for perception with a tripartite division between unconscious vision for action, conscious vision (...) for perception, and unconscious vision for perception. The combination excluded by the tripartite division is the possibility of conscious vision for action. But are there good grounds for concluding that there is no conscious vision for action? There is now overwhelming evidence that illusions and perceived size can have a significant effect on action (Bruno & Franz, 2009; Dassonville & Bala, 2004; Franz & Gegenfurtner, 2008; McIntosh & Lashley, 2008). There is also suggestive evidence that any sophisticated visual behavior requires collaboration between the two visual streams at every stage of the process (Schenk & McIntosh, 2010). I nonetheless want to make a case for the tripartite division between unconscious vision for action, conscious vision for perception, and unconscious vision for perception. My aim here is not to refute the evidence showing that conscious vision can affect action but rather to argue (a) that we cannot gain cognitive access to action-guiding dorsal stream representations, and (b) that these representations do not correlate with phenomenal consciousness. This vindicates the semi-conservative view that the dissociation hypothesis is best understood as a tripartite division. (shrink)

David Milner and Melvyn Goodale, and the many psychologists and philosophers who have been influenced by their work, claim that ‘the visual system that gives us our visual experience of the world is not the same system that guides our movements in the world’. The arguments that have been offered for this surprising claim place considerable weight on two sources of evidence — visual form agnosia and the reaching behaviour of normal subjects when picking up objects that induce (...) visual illusions. The present article shows that, if we are careful to consider the possibility that a demonstrative gesture can contribute content to a conscious experience, then neither source of evidence is compelling. (shrink)

here was a brief inaugural session of the Association for the Scientific Study of Consciousness during the Psychonomic Society Conference in Los Angeles in November 1995, but the first full conference of the Association was held this June in the very pleasant surroundings of the Claremont Colleges. Being at this conference was very different from being at ‘Tucson II’ the previous year. This was a less ballyhooed, more intimate event, maybe less exciting, and less intellectually eclectic, but also perhaps more (...) conducive to serious scientific exchange. Certainly the roster of speakers was replete with luminaries of the consciousness studies movement, and highly respected names from psychology, neuroscience and philosophy: Christof Koch, Bernard Baars, Ned Block, Philip Merikle, Daniel Schacter, Larry Jacoby, Walter Freeman, Valerie Hardcastle, both Churchlands, Melvyn Goodale, Owen Flanagan . . . to unfairly pick out just a few. (shrink)

In this paper I present a psychofunctionalist argument for conceptualism, the thesis that conscious visual experience is a conceptual state rather than a nonconceptual state. The argument draws on the holistic character of functionalist accounts of mind, together with the “Two Visual Systems Hypothesis” notably defended by Melvyn Goodale and David Milner.

Neuropsychological findings used to motivate the "two visual systems" hypothesis have been taken to endanger a pair of widely accepted claims about spatial representation in conscious visual experience. The first is the claim that visual experience represents 3-D space around the perceiver using an egocentric frame of reference. The second is the claim that there is a constitutive link between the spatial contents of visual experience and the perceiver's bodily actions. In this paper, I review and assess three main sources (...) of evidence for the two visual systems hypothesis. I argue that the best interpretation of the evidence is in fact consistent with both claims. I conclude with some brief remarks on the relation between visual consciousness and rational agency. (shrink)

In a publication of 1831 later seen as a milestone in the development of chemistry, Justus Liebig announced a new apparatus for the analysis of organic compounds and provided analytical results for fifteen substances. In this paper we used the detailed descriptions published by Liebig in 1837 to reconstruct his apparatus and methods for hydrogen, carbon and nitrogen analysis. Our replications of his analyses of racemic acid, cinchonine, narcotine, and urea reveal that his two pieces of apparatus give excellent results (...) for carbon and hydrogen content, but erratic results for nitrogen. The results corroborate the assessments of Liebig and his contemporaries, and show that the analytical method for carbon and hydrogen analysis was remarkably accurate. We offer this case, with its convincing replicability, not only to clarify the nature of Liebig's innovations, but also as a new model for understanding broader contested issues in the philosophy and sociology of science. Our analysis suggests that the great shift in science from gentlemanly avocation to professional vocation was tightly linked to laboratory practice, and not just to social networks and context. It also provides the basis for a critique of H. M. Collins's theory of the 'experimenters' regress'. (shrink)