Arien Mack and Irvin Rock make the radical claim that there is no conscious perception of the visual world without attention to it. Many people believe that merely by opening their eyes, they see everything in their field of view; in fact, a line of psychological research has been taken as evidence of the existence of so-called preattentional perception. In Inattentional Blindness, Arien Mack and Irvin Rock make the radical claim that there is no such thing—that there is no conscious perception of the visual world without attention to it. The authors present a narrative chronicle of their research. Thus, the reader follows the trail that led to the final conclusions, learning why initial hypotheses and explanations were discarded or revised, and how new questions arose along the way. The phenomenon of inattentional blindness has theoretical importance for cognitive psychologists studying perception, attention, and consciousness, as well as for philosophers and neuroscientists interested in the problem of consciousness. Bradford Books imprint

A principle of perceptual organization, called uniform connectedness (DC), is described, and a theoretical approach to perceptual organization is proposed in which this principle plays a fundamental role. The principle of DC states that closed regions of homogeneous properties-such as lightness, chromatic color, texture, and so forth-tend to be perceived initially as single units. We demonstrate its effects and show that they occur even when opposed by powerful grouping principles such as proximity and similarity. We argue that DC cannot be reduced to such grouping principles, because it is not a form of grouping at all. We then propose a theoretical framework within which DC accounts for the initial (or entry level) organization of the visual field into primitive units. Classical principles of grouping operate after DC, creating superordinate units consisting of two or more basic-level units. Parsing processes also operate after DC, dividing basic-level units into subordinate parts. DC in the retinal image is proposed to be a necessary, but not a sufficient, condition for unit formation, since connected elements on the retina that are perceived to lie in separate depth planes fail to be perceived as units. This fact, together with other evidence that the Gestalt principles of grouping are based on perceived (rather than retinal) relations, suggests that the organization of visual stimulation into DC objects is ultimately achieved within a relatively late, postconstancy representation of environmental surfaces. The implications ofthis possibility are discussed in light of present theories of visual perception.In 1923, Max Wertheimer raised the fundamental question of perceptual organization: Why is it that people perceive an organized visual world consisting of discrete objects coherently arranged in space? Without some process of organization, he argued, perception should consist of a chaotic juxtaposition of different elementary sensations based on the intensities and colors registered by individual retinal receptors. Wertheimer recognized that perception cannot be explained by the mere presence of an image containing two-dimensional (2-D) regions that correspond to external objects. Rather, processesof organization within the visual nervous system must be hypothesized as appropriately unifying receptor stimulation that arises from a single object and as separating that which arises from two or more different objects.Wertheimer's major contribution to the solution of this problem was his proposal that perception organizes stimulation by grouping elements together according to certain properties present in the retinal image. He initially inves-

Observers were presented with an object whose visual shape, because of optical distortion, differed considerably from its tactual shape. After simultaneously grasping and viewing the object, the observers were required to indicate their impression of it by drawing it or by matching another object to it. The results reveal that vision is strongly dominant, often without the observer's being aware of a conflict.

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