The time course of preview search with color-defined, not luminance-defined, stimuli

We examined the time course of preview search, using stimuli that were defined by color, but not by luminance changes. We demonstrate that, under these conditions, search performance in a preview condition improved selectively over time, relative to a baseline condition in which all the items appeared together. The data confirm earlier reports from Humphreys, Kyllinsbaek, et al. (2004) and Watson and Humphreys (1997), who used luminance-defined stimuli and showed a long time course to preview search. The data contradict Donk and Verburg (2004), who argued that the preview benefit was instantaneous but did not include baseline conditions with which to test for any influence of distractors equivalent to the old items in preview search, even under nonpreview conditions. The data support the proposal that the prioritization of new items in preview search is a time-consuming business.     

Rethinking perceptual organization: The role of uniform connectedness

A principle of perceptual organization, calleduniform connectedness (UC), is described, and a theoretical approach to perceptual organization is proposed in which this principle plays a fundamental role. The principle of UC 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 UC 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 UC accounts for the initial (orentry level) organization of the visual field into primitive units. Classical principles of grouping operate after UC, creating superordinate units consisting of two or more basic-level units. Parsing processes also operate after UC, dividing basic-level units into subordinate parts. UC 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 onperceived (rather than retinal) relations, suggests that the organization of visual stimulation into UC objects is ultimately achieved within a relatively late, postconstancy representation of environmental surfaces. The implications of this possibility are discussed in light of present theories of visual perception.     

On the nature and order of organizational processing: A reply to Peterson

Several points in the original article by Palmer and Rock (1994) are clarified in light of Peterson’s (1994) commentary. First, we address several issues related to the nature and order of organizational processes in our theory. We argue that many of her objections result from misconceptions about our theory. We attempt to clarify the relevant issues, including the fact that we intended the theory to describe an ordering of processes in cascade rather than as a sequence of classical discrete stages. Second, we discuss Peterson’s objections to our discussion of her findings on the relation between figure-ground processing and object recognition. We argue against her “prefigural recognition” proposal on logical grounds and provide an alternative account of her findings in terms of our theory.     

Perception without attention: results of a new method.

Having found by the use of a new method for examining perception without attention that grouping and texture segregation do not seem to occur (see Mack, Tang, Tuma, Kahn, & Rock (1992) Cognitive Psychology, 24, we go on to ask what is perceived without attention using this new method. Our subjects receive only one inattention trial in a sequence of trials involving a visual distraction task. In addition to the distraction task in the inattention trial, subjects received a stimulus of which they had no prior knowledge or expectation and were questioned or tested directly afterward for their perception of that stimulus. Two subsequent trials containing test stimuli serve as within-subject controls. The results of a series of experiments indicate that the presence of one or more stimulus objects and their locations are preattentively perceived, as is their color, but shape is not. Because individual items are detected without attention, we conclude that perceptual organization is initially based on a principle in which connected regions of uniform stimulation are inferred to be discrete units (the principle of uniform connectedness). One striking, unexpected finding is that without attention many subjects have no awareness at all of the stimulus object, an effect we call inattentional blindness.     

Immediate correction and adaptation based on viewing a prismatically displaced scene

It was shown that when observers view a scene of a room through displacing prisms there is an immediate correction of the prismatic distortion. Objects appear to lie in a direction closer to their true direction than to that produced by the refraction of the prisms. It was also shown that a brief period of exposure to the prismatically viewed scene, without movement or sight of the body, results in substantial adaptation to the displacement.     

Sex-Related HIV/AIDS Prevention Among African American College Students: Issues for Preventive Counseling

This study examined condom use during oral and anal sex among 1,593 African American male and female college undergraduates. Findings suggest a high level of concordance between men and women on several measures. However, female participants were more likely to use condoms during oral and anal sex than were male participants.     

Inglehart's Materialism-Postmaterialism Concept: Clarifying the Dimensionality Debate Through Rokeach's Model of Social Values1

This paper addresses an ongoing debate concerning the dimensionality of Inglehart's (1971, 1977, 1981, 1990) concept of materialism-postmaterialism. According to Inglehart, this concept is unidimensional, distinct from the traditional left-right political belief continuum, and central to explaining the changes taking place in the values of advanced industrial societies. To date, the debate has sought answers in different item sets, factor analytic solutions, and rotations. This paper approaches the problem through psychological models of social values. Materialism-postmaterialism, it is argued, involves a prioritizing of values from two orthogonal value orientations which have grown out of the work of Rokeach (1973): national strength and order and international harmony and equality.