Five aspects of visual change detection are reviewed. The first concerns the concept of change itself, in particular the ways it differs from the related notions of motion and difference. The second involves the various methodological approaches that have been developed to study change detection; it is shown that under a variety of conditions observers are often unable to see large changes directly in their field of view. Next, it is argued that this “change blindness” indicates that focused attention is (...) needed to detect change, and that this can help map out the nature of visual attention. The fourth aspect concerns how these results affect our understanding of visual perception—for example, the implication that a sparse, dynamic representation underlies much of our visual experience. Finally, a brief discussion is presented concerning the limits to our current understanding of change detection. (shrink)

It is an orthodoxy in cognitive science that perception can occur unconsciously. Recently, Hakwan Lau, Megan Peters and Ian Phillips have argued that this orthodoxy may be mistaken. They argue that many purported cases of unconscious perception fail to rule out low degrees of conscious awareness while others fail to establish genuine perception. This paper presents a case of unconscious perception that avoids these problems. It also advances a general principle of ‘phenomenal coherence’ that can insulate some forms of evidence (...) for unconscious perception from the methodological critiques of Lau, Peters and Phillips. (shrink)

Contextual regularities, that is, objects’ tendency to appear with certain other objects, facilitate the processing of visual scenes and confer contextually incongruent objects with a special attentional status. This study was aimed at investigating the mechanisms underlying this attentional advantage using Binocular Rivalry . In two experiments, congruent and incongruent images were pitted against each other, yielding a version of BR in which two objects rival within a given scene. Incongruent objects predominated in awareness longer than congruent ones. This effect (...) stemmed from the fact that their dominance epochs lasted longer on the average than those of congruent objects, suggesting a difficulty to disengage attention from such objects. On the other hand, no support was found for the notion that incongruent objects also attract attention. (shrink)

Change blindness illustrates a remarkable limitation in visual processing by demonstrating that substantial changes in a visual scene can go undetected. Because these changes can ultimately be detected using top–down driven search processes, many theories assign a central role to spatial attention in overcoming change blindness. Surprisingly, it has been reported that change blindness can occur during blink-contingent changes even when observers fixate the changing location [O’Regan, J. K., Deubel, H., Clark, J. J., & Rensink, R. A. . Picture changes (...) during blinks: Looking without seeing and seeing without looking. Visual Cognition, 7, 191–212]. However, eye blinks produce a transient disruption of vision that is independent of any associated changes in the retinal image. We determined whether these ‘attentive blank stares’ could occur in the absence of blink-mediated visual suppression. Using a flicker change-blindness paradigm we confirm that despite direct attentive fixations, obvious scene changes often remain undetected. We conclude that change detection involves object or feature based attentional mechanisms, which can be ‘misdirected’ despite the allocation of spatial attention to the position of the change. (shrink)

Changes made during a brief visual interruption sometimes go undetected, even when the object undergoing the change is at the center of the observer's interest and spatial attention. This study examined two potentially important attentional variables in change blindness: spatial distribution, manipulated via set size, and detail level, varied by having the change at either the global or local level of a compound letter. Experiment 1 revealed that both types of change were equally detectable in a single item, but that (...) global change was detected more readily when attention was distributed among several items. Variation of target level probability in Experiment 2 showed further that observers could flexibly set the detail level in monitoring both single and multiple items. Sensitivity to change therefore depends not only on the spatial focus of attention; it depends critically on the match between the detail level of the change and the level-readiness of the observer. (shrink)

Several studies (e.g., Becklen & Cervone, 1983; Mack & Rock, 1998; Neisser & Becklen, 1975) have found that observers attending to a particular object or event often fail to report the presence of unexpected items. This has been interpreted as inattentional blindness (IB), a failure to see unattended items (Mack & Rock, 1998). Meanwhile, other studies (e.g., Pashler, 1988; Phillips, 1974; Rensink et al., 1997; Simons, 1996) have found that observers often fail to report the presence of large changes in (...) a display when these changes occur simultaneously with a transient such as an eye movement or flash of the display. This has been interpreted as change blindness (CB), a failure to see unattended changes (Rensink et al., 1997). In both cases there is a striking failure to report an object or event that would be quite visible under other circumstances. And in both cases there is a widespread (although not universal) belief that the underlying cause has to do with the absence of attention. The question then arises as to how these effects might be related. Is CB the same thing as IB? If not, what is the relation between them? And given that these phenomena deal with failures of subjective perception, what can they teach us about the nature of our visual experience? In particular, what can they teach us about the role played by visual attention? (shrink)

An overview is presented of the ways that change blindness has been applied to the study of various issues in perception and cognition. Topics include mechanisms of change perception, allocation of attention, nonconscious perception, and cognitive beliefs. Recent work using change blindness to investigate these topics is surveyed, along with a brief discussion of some of the ways that these approaches may further develop over the next few years.

& Awareness of change within a visual scene only occurs in subjects were aware of, replicated those attentional effects, but the presence of focused attention. When two versions of a.

b>—Several paradigms (e.g. change blindness, inattentional blindness, transsaccadic integra- tion) indicate that observers are often very poor at reporting changes to their visual environment. Such evidence has been used to suggest that the spatio-temporal coherence needed to represent change can only occur in the presence of focused attention. However, those studies almost always rely on explicit reports. It remains a possibility that the visual system can implicitly detect change, but that in the absence of focused attention, the change does not (...) reach awareness and consequently is not reported. To test this possibility, we used a simple change detection paradigm coupled with a speeded orien- tation discrimination task. Even when observers reported being unaware of a change in an item’s orientation, its nal orientation effectively biased their response in the orientation discrimination task. Both in aware and unaware trials, errors were most frequent when the changed item and the probe had incongruent orientations. These results demonstrate that the _nature _of the change can be represented in the absence of awareness. (shrink)