Online research in philosophy

Vision constitutes an interesting domain, or range of domains, for debate over the extended mind thesis, the idea that minds physically extend beyond the boundaries of the body. In part this is because vision and visual experience more particularly are sometimes presented as a kind of line in the sand for what we might call externalist creep about the mind: once all reasonable concessions have been made to externalists about the mind, visual experience marks a line beyond which lies a safe haven for individualists. Here I want to put a little more pressure on such a view of visual experience, as well as to offer a more constructive, positive argument in defense of the idea of extended vision.

Large changes in a scene often become difficult to notice if made during an eye movement, image flicker, movie cut, or other such disturbance. It is argued here that this _change blindness_ can serve as a useful tool to explore various aspects of vision. This argument centers around the proposal that focused attention is needed for the explicit perception of change. Given this, the study of change perception can provide a useful way to determine the nature of visual attention, and to cast new light on the way that it is?and is not?involved in visual perception. To illustrate the power of this approach, this paper surveys its use in exploring three different aspects of vision. The first concerns the general nature of _seeing_. To explain why change blindness can be easily induced in experiments but apparently not in everyday life, it is proposed that perception involves a _virtual representation_, where object representations do not accumulate, but are formed as needed. An architecture containing both attentional and nonattentional streams is proposed as a way to implement this scheme. The second aspect concerns the ability of observers to detect change even when they have no visual experience of it. This _sensing_ is found to take on at least two forms: detection without visual experience (but still with conscious awareness), and detection without any awareness at all. It is proposed that these are both due to the operation of a nonattentional visual stream. The final aspect considered is the nature of visual attention itself?the mechanisms involved when _scrutinizing_ items. Experiments using controlled stimuli show the existence of various limits on visual search for change. It is shown that these limits provide a powerful means to map out the attentional mechanisms involved.

Reflection on the fine-grained information required for visual guidance of action has suggested that visual content is non-conceptual. I argue that in a common type of visually guided action, namely the use of manipulable artefacts, vision has conceptual content. Specifically, I show that these actions require visual attention and that concepts are involved in directing attention. In acting with artefacts, there is a way of doing it right as determined by the artefact’s conventional use. Attention must reflect our understanding of the function and appropriate ways to use these artefacts, understanding that requires possession of the relevant concept. As a result, we attend to the artefact’s relevant functional properties. In these cases, attention is structured by concepts. This discussion has a bearing on the dual visual stream hypothesis. While it is often held that the two visual streams are functionally independent, the argument of this essay is that the constraints on attention suggest a functional interaction between them.

Alva Noë’s version of the enactive conception in _Action in Perception_ is an important contribution to the study of visual perception. First, I argue, however, that it is unclear (at best) whether, as the enactivists claim, work on change blindness supports the denial of the existence of detailed visual representations. Second, I elaborate on what Noë calls the ‘puzzle of perceptual presence’. Thirdly, I question the enactivist account of perceptual constancy. Finally, I draw attention to the tensions between enactivism and two trends in cognitive neuroscience: the two-visual systems model of human vision and the theory of internal forward models of action.

This article defends the claim that a significant part of visual perception (called “early vision”) is impervious to the influence of beliefs, expectations or knowledge. We examine a wide range of empirical evidence that has been cited in support of the continuity of vision and cognition and argue that the evidence either shows within- vision top-down effects, or else the extra-visual effects that are demonstrated occur before the operation of the autonomous early vision system (through the allocation of focal attention) or after the visual system has produced its 3D shape-description (through the intervention of post-visual decision processes).

The target article proposes that visual experience arises when sensorimotor contingencies are exploited in perception. This novel analysis of visual experience fares no better than the other proposals that the article rightly dismisses, and for the same reasons. Extracting invariants may be needed for recognition, but it is neither necessary nor sufficient for having a visual experience. While the idea that vision involves the active extraction of sensorimotor invariants has merit, it does not replace the need for perceptual representations. Vision is not just for the immediate controlling of action; it is also for finding out about the world, from which inferences may be drawn and beliefs changed.

The problem of the richness of visual experience is that of finding principled grounds for claims about how much of the world a person actually sees at any given moment. It is argued that there are suggestive parallels between the two-component analysis of experience defended by Wilfrid Sellars, and certain recently advanced information processing accounts of visual perception. Sellars' later account of experience is examined in detail, and it is argued that there are good reasons in support of the claim that the sensory nonconceptual content of experience can vary independently of conceptual awareness. It is argued that the Sellarsian analysis is not undermined by recent work on change blindness and related phenomena; a model of visual experience developed by Ronald Rensink is shown to be in essential harmony with the framework provided by Sellars, and provides a satisfactory answer to the problem of the richness of visual experience.

The strong sensorimotor account of perception gives self-induced movements two constitutive roles in explaining visual consciousness. The first says that self-induced movements are vehicles of visual awareness, and for this reason consciousness ‘does not happen in the brain only’. The second says that the phenomenal nature of visual experiences is consists in the action-directing content of vision. In response I suggest, first, that the sense in which visual awareness is active should be explained by appeal to the role of attention in visual consciousness, rather than self-induced movements; and second, that the sense in which perceptual consciousness does not happen in the brain only should be explained by appeal to the relational nature of perceptual consciousness, appeal to which also shows why links with action cannot exhaust phenomenal content.