In this commentary we review evidence concerning the true sensitivity of viewers to visual changes in scene images. We argue that the data strongly suggest that "change blindness" experiments, while revealing of a variety of important constraints on encoding and retrieval processes in visual memory, do not demonstrate the lack of scene representations assumed by O&N. Instead, the data suggest that detailed scene representations can be generated and survive relatively intact across views (e.g., across saccades) and over extended periods of time. Of course, as we have known at least since the seminal work of Sperling (1960) and Averbach and Coriell (1961), these representations are not "iconic" in nature. CommentaryIn the target article, O'Regan and Nöe (O&N) reject the assumption prevalent in computational vision and visual cognition that the visual system generates an accurate, detailed, and stable scene representation. Instead, O&N propose that the experience of visual coherence is an illusion brought about by the fact that visual information can be sampled from the world when needed via sensory motor interaction, i.e., via shifts of attention and fixation. In this view, there is no need for an internal scene representation because the world can serve as its own external memory, and it is the ability of the system to sample this outside memory at will in the service of ongoing perceptual and cognitive processing that produces perceptual experience.O&N suggest that an important prediction of their theory is that viewers should be insensitive to what appear to be relatively large and obvious changes when detecting the change depends on visual memory rather than on the perception of image transients; that is, the theory predicts "change blindness". Aside from the issue of whether the theory motivated the experiments or vice versa (in fact, change blindness as a phenomenon has been known at least since the mid-1970s, and the most recent demonstrations of these phenomena in images of real-world scenes were produced by McConkie and

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In visual science the term filling-in is used in different ways, which often leads to confusion. This target article presents a taxonomy of perceptual completion phenomena to organize and clarify theoretical and empirical discussion. Examples of boundary completion (illusory contours) and featural completion (color, brightness, motion, texture, and depth) are examined, and single-cell studies relevant to filling-in are reviewed and assessed. Filling-in issues must be understood in relation to theoretical issues about neural–perceptual isomorphism and linking propositions. Six main conclusions are drawn: (1) visual filling-in comprises a multitude of different perceptual completion phenomena; (2) certain forms of visual completion seem to involve spatially propagating neural activity (neural filling-in) and so, contrary to Dennett's (1991; 1992) recent discussion of filling-in, cannot be described as results of the brain's “ignoring an absence” or “jumping to a conclusion”; (3) in certain cases perceptual completion seems to have measurable effects that depend on neural signals representing a presence rather than ignoring an absence; (4) neural filling-in does not imply either “analytic isomorphism” or “Cartesian materialism,” and thus the notion of the bridge locus – a particular neural stage that forms the immediate substrate of perceptual experience – is problematic and should be abandoned; (5) to reject the representational conception of vision in favor of an “enactive” or “animate” conception reduces the importance of filling-in as a theoretical category in the explanation of vision; and (6) the evaluation of perceptual content should not be determined by “subpersonal” considerations about internal processing, but rather by considerations about the task of vision at the level of the animal or person interacting with the world.

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