Biomedical subjects

Daniel T Levin

Publications and source records attributed to Daniel T Levin.

13 recordsLinked to original sources

PubMed2006

Change blindness blindness: beliefs about the roles of intention and scene complexity in change detection.

Observers have difficulty detecting visual changes. However, they are unaware of this inability, suggesting that people do not have an accurate understanding of visual processes. We explored whether this error is related to participants' beliefs about the roles of intention and scene complexity in detecting changes. In Experiment 1 participants had a higher failure rate for detecting changes in an incidental change detection task than an intentional change detection task. This effect of intention was greatest for complex scenes. However, participants predicted equal levels of change detection for both types of changes across scene complexity. In Experiment 2, emphasizing the differences between intentional and incidental tasks allowed participants to make predictions that were less inaccurate. In Experiment 3, using more sensitive measures and accounting for individual differences did not further improve predictions. These findings suggest that adults do not fully understand the role of intention and scene complexity in change detection.

Awareness↗

PubMed2006

Distortions in the perceived lightness of faces: the role of race categories.

Although lightness perception is clearly influenced by contextual factors, it is not known whether knowledge about the reflectance of specific objects also affects their lightness. Recent research by O. H. MacLin and R. Malpass (2003) suggests that subjects label Black faces as darker than White faces, so in the current experiments, an adjustment methodology was used to test the degree to which expectations about the relative skin tone associated with faces of varying races affect the perceived lightness of those faces. White faces were consistently judged to be relatively lighter than Black faces, even for racially ambiguous faces that were disambiguated by labels. Accordingly, relatively abstract expectations about the relative reflectance of objects can affect their perceived lightness.

Adolescent↗

PubMed2006

Change blindness and visual memory: visual representations get rich and act poor.

Change blindness is often taken as evidence that visual representations are impoverished, while successful recognition of specific objects is taken as evidence that they are richly detailed. In the current experiments, participants performed cover tasks that required each object in a display to be attended. Change detection trials were unexpectedly introduced and surprise recognition tests were given for nonchanging displays. For both change detection and recognition, participants had to distinguish objects from the same basic-level category, making it likely that specific visual information had to be used for successful performance. Although recognition was above chance, incidental change detection usually remained at floor. These results help reconcile demonstrations of poor change detection with demonstrations of good memory because they suggest that the capability to store visual information in memory is not reflected by the visual system's tendency to utilize these representations for purposes of detecting unexpected changes.

Adult↗

PubMed2005

Inattentional blindness for a noxious multimodal stimulus.

Previous research has shown that people can miss salient stimuli outside the focus of their attention. This phenomenon, called inattentional blindness, typically is observed when people are given a task requiring them to focus their attention on one aspect of a complex visual scene. While participants are doing this task, an unexpected stimulus appears, and participants' awareness of it is tested shortly thereafter. In the present experiments, noxious bimodal stimuli were used as a test case to measure the strength of inattentional blindness. We tested whether participants would notice a person enter a scene and scratch her fingernails down a chalkboard (thus making a sound called a "gride"). A large proportion of participants failed to detect this event even when the noxious audio associated with it was strengthened and isolated in time from surrounding noises.

Awareness↗

PubMed2004

No pause for a brief disruption: failures of visual awareness during ongoing events.

Past research has repeatedly documented the close relationship between visual attention and awareness. Most recently, research exploring change blindness, inattentional blindness, repetition blindness, and the attentional blink has converged on the conclusion that attention to one aspect of a scene or event may lead to a highly circumscribed awareness of only the specific information attended, while other information, even that which is spatially or temporally nearby can go completely unnoticed. In the present report, we extend these observations to the dynamic allocation of attention during a well-structured meaningful event. In two experiments, subjects viewed brief videos of simple events and were told to pay close attention to them. During the events, an unexpected disruption consisting of a brief low spatial frequency motion field occurred. Despite intensive questioning and opportunities for recognition, the majority of subjects reported no awareness of 200, 400, or 600 ms disruptions. In a second experiment, blank-screen disruptions were added, and these resulted in no increase in detection. We conclude that visual attention may result in far more transitory awareness of visual information than previously appreciated.

Attention↗

PubMed2004

Knowledge about the probability of change affects change detection performance.

The visual system continually selects some information for processing while bypassing the processing of other information, and as a consequence, participants often fail to notice large changes to visual stimuli. In the present studies, the authors investigated whether knowledge about the probability of particular changes occurring over time increased the likelihood that changes that were likely to occur in the real world (probable changes) would be detected. The results of two experiments showed that participants were more likely to detect probable changes. This occurred whether or not they were processing the scene in a meaningful manner or actively searching the scene for changes. Furthermore, participants were unable to accurately predict change detection performance for probable and improbable changes.

Cognition↗

PubMed2004

Nothing compares 2 views: change blindness can occur despite preserved access to the changed information.

Change blindness, the failure to detect visual changes that occur during a disruption, has increasingly been used to infer the nature of internal representations. If every change were detected, detailed representations of the world would have to be stored and accessible. However, because many changes are not detected, visual representations might not be complete, and access to them might be limited. Using change detection to infer the completeness of visual representations requires an understanding of the reasons for change blindness. This article provides empirical support for one such reason: change blindness resulting from the failure to compare retained representations of both the pre- and postchange information. Even when unaware of changes, observers still retained information about both the pre- and postchange objects on the same trial.

Awareness↗

PubMed2003

The relationship between change detection and recognition of centrally attended objects in motion pictures.

Observers typically detect changes to central objects more readily than changes to marginal objects, but they sometimes miss changes to central, attended objects as well. However, even if observers do not report such changes, they may be able to recognize the changed object. In three experiments we explored change detection and recognition memory for several types of changes to central objects in motion pictures. Observers who failed to detect a change still performed at above chance levels on a recognition task in almost all conditions. In addition, observers who detected the change were no more accurate in their recognition than those who did not detect the change. Despite large differences in the detectability of changes across conditions, those observers who missed the change did not vary in their ability to recognize the changing object.

Attention↗

PubMed2003

The role of representational volatility in recognizing pre- and postchange objects.

Theories relating attention to change blindness (CB) imply that representations of objects in the focus of attention are stable and coherent. However, CB occurs for objects in the focus of attention. Here, we explore this apparent contradiction and the possibility that changes can be detected without having a complete and stable representation of the prechange object. The first experiment required observers to recognize a prechange object and a postchange object after viewing arrays of various sizes in which the prechange object was replaced by the postchange object after a brief delay. Results indicated that the representation of the prechange object was strong enough to cue a change but not strong enough to support accurate recognition. The remaining experiments demonstrated that the representation of the prechange object is volatile in that a shift in the display or the presence of a postchange object can disrupt the representation. These findings add to current theories of attention and representations by showing that attention may result in volatile representations that can support change detection without supporting accurate recognition.

Humans↗

PubMed2002

Evidence for preserved representations in change blindness.

People often fail to detect large changes to scenes, provided that the changes occur during a visual disruption. This phenomenon, known as "change blindness," occurs both in the laboratory and in real-world situations in which changes occur unexpectedly. The pervasiveness of the inability to detect changes is consistent with the theoretical notion that we internally represent relatively little information from our visual world from one glance at a scene to the next. However, evidence for change blindness does not necessarily imply the absence of such a representation---people could also miss changes if they fail to compare an existing representation of the pre-change scene to the post-change scene. In three experiments, we show that people often do have a representation of some aspects of the pre-change scene even when they fail to report the change. And, in fact, they appear to "discover" this memory and can explicitly report details of a changed object in response to probing questions. The results of these real-world change detection studies are discussed in the context of broader claims about change blindness.

Attention↗

PubMed2002

False predictions about the detectability of visual changes: the role of beliefs about attention, memory, and the continuity of attended objects in causing change blindness blindness.

Recently, a number of experiments have emphasized the degree to which subjects fail to detect large changes in visual scenes. This finding, referred to as "change blindness," is often considered surprising because many people have the intuition that such changes should be easy to detect. documented this intuition by showing that the majority of subjects believe they would notice changes that are actually very rarely detected. Thus subjects exhibit a metacognitive error we refer to as "change blindness blindness." Here, we test whether CBB is caused by a misestimation of the perceptual experience associated with visual changes and show that it persists even when the pre- and postchange views are separated by long delays. In addition, subjects overestimate their change detection ability both when the relevant changes are illustrated by still pictures, and when they are illustrated using videos showing the changes occurring in real time. We conclude that CBB is a robust phenomenon that cannot be accounted for by failure to understand the specific perceptual experience associated with a change.

Adult↗

PubMed2002

Categorical perception of race.

Traditionally, research demonstrating categorical perception (CP) has assumed that CP occurs only in cases where natural continua are divided categorically by long-term learning or innate perceptual programming. More recent research suggests that this may not be true, and that even novel continua between novel stimuli such as unfamiliar faces can show CP effects as well. Given this, we ask whether CP is dependent solely on the representation of individual stimuli, or whether stimulus categories themselves can also cause CP. Here, we test the hypothesis that continua between individual faces that cross the categorical boundary between races show an enhanced CP effect. We find that continua running from a black face to a white face do, indeed, show stronger CP effects than continua between two black faces or two white faces. This suggests that CP effects are enhanced when continua run between two distinctly represented individual stimuli, and are further enhanced when those individuals are, in turn, members of different stimulus categories.

Discrimination, Psychological↗

PubMed2002

Memory for centrally attended changing objects in an incidental real-world change detection paradigm.

People often have difficulty detecting visual changes in scenes, a phenomenon referred to as 'change blindness'. Although change blindness is usually observed in pictures of objects that are not the focus of attention, it also occurs for attended objects in the real world. Here, we further explore the finding that many participants fail to detect the unexpected substitution of one conversation partner for another. We show that change blindness for a conversation partner occurs in a variety of situations. Furthermore, when tested with a photographic lineup following the change, participants who noticed the substitution showed better memory for both pre- and post-change experimenters than participants who did not detect the change. We conclude that change blindness in this case is associated with relatively ineffective or inaccessible representations of previously attended objects, and we contrast these results with others indicating that change blindness arises from a failure to compare the original and changed object.

Adolescent↗