Conscious Vision for Action Versus Unconscious Vision for Action?

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.     

Two visual systems and two theories of perception: An attempt to reconcile the constructivist and ecological approaches

The two contrasting theoretical approaches to visual perception, the constructivist and the ecological, are briefly presented and illustrated through their analyses of space and size perception. Earlier calls for their reconciliation and unification are reviewed. Neurophysiological, neuropsychological, and psychophysical evidence for the existence of two quite distinct visual systems, the ventral and the dorsal, is presented. These two perceptual systems differ in their functions; the ventral system's central function is that of identification, while the dorsal system is mainly engaged in the visual control of motor behavior. The strong parallels between the ecological approach and the functioning of the dorsal system, and between the constructivist approach and the functioning of the ventral system are noted. It is also shown that the experimental paradigms used by the proponents of these two approaches match the functions of the respective visual systems. A dual-process approach to visual perception emerges from this analysis, with the ecological-dorsal process transpiring mainly without conscious awareness, while the constructivist-ventral process is normally conscious. Some implications of this dual-process approach to visual-perceptual phenomena are presented, with emphasis on space perception.     

动允直接知觉的共鸣原理

传统认知理论认为我们只能间接知觉动允,而生态认知心理学则认为对动允的知觉是个体与环境信息直接共鸣的过程。生态认知心理学首先判定动允并不是存在于我们头脑中的认识,而是实际存在于个体-环境系统中的事实,对动允的直接知觉就是对动允的检测而非推测,是对动允信息的拾取而非对记忆内容的提取。这种直接知觉表现为身体的相关动作机制（动作神经元、肌肉组织等）与环境中动允信息的共鸣。进化与学习在共鸣的形成与发展中具有重要作用。     

The Ecology of Human-Machine Systems I: Introduction

A symposium entitled, The Ecology of Human-Machine Systems, was held at the Fifth International Conference on Event Perception and Action. This sympo- sium examined the challenges that human-machine systems hold for an ecological approach to perception, cognition, and action and the promises that an ecological approach holds for problems that traditionally have been the domain of human factors psychology. The presenters from this symposium have been invited to submit articles about an applied ecological psychology to Ecological Psychology. Articles that are accepted for publication will be appearing in future issues of this journal. It is hoped that these articles will stimulate productive interaction between ecological and human factors psychology. This correspondence reflects the natural affinity between ecological and human factors psychology. It examines some of the issues that distinguish basic and applied research. It also considers the contribution that ecological physics can make for improving tradi- tional approaches to task analysis. Finally, this article speculates about emerging areas of research in which the ecological approach may contribute to the design of human-machine systems.     

Computational Cognitive Neuroscience of the Visual System

ABSTRACT— Should psychologists care about functional magnetic resonance imaging (fMRI)? Within the field of visual perception, the answer to this question is an emphatic "yes." There is a long history of close interactions between psychology and neuroscience in the study of vision. In the 1980s, vision researchers developed a general framework for combining the two fields, and that framework still supports much current research. This article will briefly cover this general approach and then will illustrate how neuroimaging allows the framework to be applied to human perception. In short, fMRI can measure how information is represented in sequential stages of processing. These same representations can also be measured behaviorally. Theories of vision specify how the sequential representations participate in well-defined computations that underlie perception.     

Visual space perception and action: Introductory remarks

Vision evolved from the vital necessity to act in a dynamic environment. Following this view it is clear that perceptual processes and action planning are much more interlocked than is evident at first sight. This is especially evident in visual space perception; actions are performed in space and are guided and controlled by objects in spatial positions. Here we shortly introduce the three research camps dealing with the relationship between space perception and action: the ecological camp, the two‐visual‐systems camp, and the constructivist camp. We show that these camps emphasize and open different theoretical and empirical perspectives, but that they can be seen to complement each other. We end with an overview of the papers in this special issue.     

Defining the cortical visual systems: "what", "where", and "how"

The visual system historically has been defined as consisting of at least two broad subsystems subserving object and spatial vision. These visual processing streams have been organized both structurally as two distinct pathways in the brain, and functionally for the types of tasks that they mediate. The classic definition by Ungerleider and Mishkin labeled a ventral "what" stream to process object information and a dorsal "where" stream to process spatial information. More recently, Goodale and Milner redefined the two visual systems with a focus on the different ways in which visual information is transformed for different goals. They relabeled the dorsal stream as a "how" system for transforming visual information using an egocentric frame of reference in preparation for direct action. This paper reviews recent research from psychophysics, neurophysiology, neuropsychology and neuroimaging to define the roles of the ventral and dorsal visual processing streams. We discuss a possible solution that allows for both "where" and "how" systems that are functionally and structurally organized within the posterior parietal lobe.     

Visual processing for action resists similarity of relevant and irrelevant object features

It has been suggested that the human brain processes visual information in different manners, depending on whether the information is used for perception or for action control. This distinction has been criticized for the lack of behavioral dissociations that unambiguously support the proposed two-visual-pathways model. Here we present a new and simple dissociation between vision for perception and vision for action: Perceptual judgments are affected by the similarity of relevant and irrelevant stimulus features, while object-oriented actions are not. This dissociation overcomes the methodological problems of previously proposed differences in terms of vulnerability to visual illusions or to variability in irrelevant object features, and it can also serve as an easily applicable behavioral indicator of underlying processing modes.     

Conscious Vision in Action

It is natural to assume that the fine‐grained and highly accurate spatial information present in visual experience is often used to guide our bodily actions. Yet this assumption has been challenged by proponents of the Two Visual Systems Hypothesis (TVSH), according to which visuomotor programming is the responsibility of a “zombie” processing stream whose sources of bottom‐up spatial information are entirely non‐conscious (Clark, 2007, 2009; Goodale & Milner, 1992, 2004a; Milner & Goodale, 1995/2006, 2008). In many formulations of TVSH, the role of conscious vision in action is limited to “recognizing objects, selecting targets for action, and determining what kinds of action, broadly speaking, to perform” (Clark, 2007, p. 570). Our aim in this study is to show that the available evidence not only fails to support this dichotomous view but actually reveals a significant role for conscious vision in motor programming, especially for actions that require deliberate attention.     

Direct Perception Requires an Animal-Dependent Concept of Specificity and of Information

Specificity and information are at center stage in ecological psychology. Nevertheless, the usual theorizing on these concepts may have made the problem of accounting for perception and action more difficult by so far underestimating the role of animals as both meaning-detectors and meaning-determiners. The usual understanding of information and specificity in ecological psychology seems neither necessary nor even compatible with ecological premises and empirical findings. I argue that a reframing of these concepts to fully take animals into account is necessary to explain perception of action-specific meanings. The reframing proposed converges on ideas from developmental systems theory and in no way concedes to inputs-followed-by-processing-followed-by-representation models. Fully acknowledging the animal for properly defining information over the animal-environment system poses no threat lawfulness, realism, or direct perception. It also invites serious consideration of self-organization and interactivism as sources for further development of ecological science.     

Getting the closer object? An information‐based dissociation between vision for perception and vision for movement in early infancy

In human adults two functionally and neuro‐anatomically separate systems exist for the use of visual information in perception and the use of visual information to control movements (Milner & Goodale, 1995 , 2008 ). We investigated whether this separation is already functioning in the early stages of the development of reaching. To this end, 6‐ and 7‐month‐old infants were presented with two identical objects at identical distances in front of an illusory Ponzo‐like background that made them appear to be located at different distances. In two further conditions without the illusory background, the two objects were presented at physically different distances. Preferential reaching outcomes indicated that the allocentric distance information contained in the illusory background affected the perception of object distance. Yet, infants' reaching kinematics were only affected by the objects' physical distance and not by the perceptual distance manipulation. These findings were taken as evidence for the two‐visual systems, as proposed by Milner and Goodale ( 2008 ), being functional in early infancy. We discuss the wider implications of this early dissociation.     

The Ecological Level of Analysis: Can Neogibsonian Principles be Applied Beyond Perception and Action?

Is it useful to apply ecological principles, developed to understand perception and action, in research areas such as social psychology? Charles (Integrative Psychological &; Behavioral Sciences 43(1) 53–66 2009) warns ecological psychologists interested in this question that much time and effort can be saved through a backwards extension to or rediscovery of the New Realism tradition. In response, we analyze what ecological psychology risks to lose with such a backwards extension and describe existing extensions of the approach not considered by Charles. According to Charles, New Realism holds that: (1) we experience reality, (2) relations are real, and (3) things are what you see when you see those things. Our arguments originate from a comparison of these principles with six recently described ecological ones: (1) organism-environment systems are the proper units of analysis, (2) environmental realities should be defined at the ecological scale, (3) behavior is emergent and self-organized, (4) perception and action are continuous and cyclic, (5) information is specificational, and (6) perception is of affordances (Richardson et al. 2008).     

Visual illusions affect both movement planning and on-line control: a multiple cue position on bias and goal-directed action

Over the last decade, there has been an interest in the impact of visual illusions on the control of action. Much of this work has been motivated by Milner and Goodale's two visual system model of visual processing. This model is based on a hypothesized dissociation between cognitive judgments and the visual control of action. It holds that action is immune to the visual context that provides the basis for the illusion-induced bias associated with cognitive judgments. Recently, Glover has challenged this position and has suggested that movement planning, but not movement execution is susceptible to visual illusions. Research from our lab is inconsistent with both models of visual-motor processing. With respect to the planning and control model, kinematic evidence shows that the impact of an illusion on manual aiming increases as the limb approaches the target. For the Ebbinghaus illusion, this involved a decrease in the time after peak velocity to accommodate the 'perceived' size of the target. For the Müller-Lyer illusion, the influence of the figure's tails increased from peak velocity to the end of the movement. Although our findings contradict a strong version of the two visual systems hypothesis, we did find dissociations between perception and action in another experiment. In this Müller-Lyer study, perceptual decisions were influenced by misjudgment of extent, while action was influenced by misjudgment of target position. Overall, our findings are consistent with the idea that it is often necessary to use visual context to make adjustments to ongoing movements.     

The Separation of Action and Perception and the Issue of Affordances

Michaels's (2000) reassessment of the relation between action and perception is endorsed. In alignment with Milner and Goodale (1995), she proposed a separation between action (i.e., control of movement) and perception (i.e., the explicit knowledge of environmental properties, including animal-referential ones), the separation being based on the reliance on different optical variables. However, how should the concept of affordances be incorporated into this scheme? We present data showing that affordances, both when perceived and acted on, are not susceptible to optical illusions. Because action and perception are distinguished on the basis of information used, but are also proposed to interact, it is hypothesized that, dependent on the task goal, "information for action" may be used in perception, and "information for perception" may be used in action. Participants may become more attuned to information for action when perception serves to acquire explicit knowledge about what the environment affords for action.     

2-D tilt and 3-D slant illusions in perception and action tasks

There is now a well established dissociation between perception and action based primarily on neuropsychological evidence [Milner and Goodale, 1995 The Visual Brain in Action (Oxford: Oxford University Press)]. Although equivocal, an important source of evidence from normal observers is that 'perceptual illusions' may affect the systems differently. We investigated the relative effects of 2-D tilt and 3-D slant illusions in the two domains, using similar tasks to those employed originally by Milner and Goodale. Subjects were required to either post a card through, or set a paddle to match the orientation of, a plane that was presented in two conditions: surrounded by a striped surface tilted between +90 degrees and -90 degrees (2-D tilt contrast), or surrounded by a disparity defined surface slanted in depth between +60 degrees and -60 degrees (3-D depth contrast). For 2-D tilt, action and perception were equally affected by the illusion, whereas in the 3-D condition they were not. Here, the illusion appeared greater in the posting than in the perceptual task. We conclude that, although no qualitative differences exist, there were quantitative differences between perception and action tasks in the binocular condition.     

Semantic and pragmatic integration in vision for action

According to an influential view, the detection of action possibilities and the selection of a plan for action are two segregated steps throughout the processing of visual information. This classical approach is committed with the assumption that two independent types of processing underlie visual perception: the semantic one, which is at the service of the identification of visually presented objects, and the pragmatic one which serves the execution of actions directed to specific parts of the same objects. However, as our knowledge of vision has improved over the years, this established view has turned out to be only an approximation. This paper sets out the details of a non-modularist approach to visual perception of action possibilities and explains how to resist the lure of cognitive segregation.     

Visual and tactual texture perception: Intersensory cooperation

In three experiments, subjects were required to make texture judgments about abrasive surfaces. Touch and vision provided comparable levels of performance when observers attempted to select the smoothest of three surfaces, but bimodal visual and tactual input led to greater accuracy. The superiority of bimodal perception was ascribed to visual guidance of tactual exploration. The elimination of visual texture cues did not impair bimodal performance if vision of hand movements were permitted. It is suggested that touch may preempt vision when both sources of texture information are simultaneously available. The results support the notion that perception is normally multimodal, since restriction of the observer to either sense in isolation produces lower levels of performance.     

Visually Controlled Locomotion: 40 years Later

Gibson's article, Visually Controlled Locomotion and Visual Orientation in Animals(1958/this issue), is the leading statement of a nonrepresentational, information-based approach to visual control. The core ideas he introduced 40 years ago resurface, explicitly or implicitly, in much contemporary work on perception and action in humans, insects, robots, and autonomous agents. The purpose of this special issue is to assess the continuing pertinence of these insights and illustrate current directions in research on visually controlled locomotion. In this article, I locate the 1958 article in the context of Gibson's emerging theory of perception, contrast information-based control with standard model-based and cybernetic control architectures, evaluate the current status of Gibson's visual control formulae, and situate visual control within an informational-dynamical approach to agent-environment systems. Locomotion is a biologically basic function, and if that can be accounted for then the problem of human space perception may appear in a new light. The question, then, is how an animal gets about by vision.     

ON RELATIVISM IN CONSTRUCTIVIST PSYCHOLOGY

Many scholars criticize constructivist approaches to psychology for culminating in a nihilistic relativism. This article reviews the problem of relativism within personal construct psychology and social constructionism. It argues that labeling constructivist approaches to psychology as essentially relativist or nonrelativist simplifies the debate by assigning indisputable characteristics to a family of theories. Both relativist and nonrelativist interpretations of personal constructivism and social constructionism are presented in suggesting that the current terms of the relativism debate often hinder constructivists, who are forced to defend themselves against charges of relativism using objectivist terminology. Some common arguments about the advantages and disadvantages of constructivist relativism are outlined and discussed. Further, the implications of relativism for constructivist ethics and action are contemplated, with particular attention paid to the roles of commitment and hermeneutic understanding. The article concludes that, while constructivist psychologists may not agree on whether to endorse or reject relativism, in order to maintain the viability of the constructivist viewpoint, they need to be able to formulate thoughtful responses to those accusing them of relativism.     

On specification and the senses

In this target article we question the assumption that perception is divided into separate domains of vision, hearing, touch, taste, and smell. We review implications of this assumption for theories of perception and for our understanding of ambient energy arrays (e.g., the optic and acoustic arrays) that are available to perceptual systems. We analyze three hypotheses about relations between ambient arrays and physical reality: (1) that there is an ambiguous relation between ambient energy arrays and physical reality, (2) that there is a unique relation between individual energy arrays and physical reality, and (3) that there is a redundant but unambiguous relation, within or across arrays, between energy arrays and physical reality. This is followed by a review of the physics of motion, focusing on the existence and status of referents for physical motion. Our review indicates that it is not possible, in principle, for there to be a unique relation between physical motion and the structure of individual energy arrays. We argue that physical motion relative to different referents is specified only in the global array, which consists of higher-order relations across different forms of energy. The existence of specificity in the global array is consistent with the idea of direct perception, and so poses a challenge to traditional, inference-based theories of perception and cognition. However, it also presents a challenge to much of the ecological approach to perception and action, which has accepted the assumption of separate senses.