Change blindness

Although at any instant we experience a rich, detailed visual world, we do not use such visual details to form a stable representation across views. Over the past five years, researchers have focused increasingly on 'change blindness' (the inability to detect changes to an object or scene) as a means to examine the nature of our representations. Experiments using a diverse range of methods and displays have produced strikingly similar results: unless a change to a visual scene produces a localizable change or transient at a specific position on the retina, generally, people will not detect it. We review theory and research motivating work on change blindness and discuss recent evidence that people are blind to changes occurring in photographs, in motion pictures and even in real-world interactions. These findings suggest that relatively little visual information is preserved from one view to the next, and question a fundamental assumption that has underlain perception research for centuries: namely, that we need to store a detailed visual representation in the mind/brain from one view to the next.     

Change blindness in driving scenes

One of the key perceptual errors that contributes to accidents on the road is ‘looking but failing to see’. Though this has previously been attributed to failures of attention or time gaps, the recent change blindness literature suggests another alternative. Researchers have proposed that we have a poor memory for the visual world, and as such, participants find it very hard to notice a change between two successive pictures providing the transients that normally catch attention are masked. Such masking can occur naturally due to blinks and saccadic suppression. It is suggested that these effects may contribute to accident liability. An experiment was undertaken to test the application of the change blindness paradigm to the driving domain. It was predicted that experienced drivers may have greater visual persistence for changed targets in a road scene provided they are relevant to a driver’s parsing of the road (i.e. if the targets are potential hazards such as pedestrians, rather than changes in background scenery). The experiment required drivers and non-drivers to view a complex driving-related visual scene that was constantly interrupted by a flash once per second. During the flashes one item in the scene was changed. This target was manipulated according to location and semantic relevance. Results showed an interaction between central and peripheral items with semantic relevance. Participants found it hard to detect central items that were inconsequential, relative to other classifications of targets. No effect of experience was noted. The results are discussed in relation to the general theoretical literature and their potential applications to the driving domain.     

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.     

Change blindness and eyewitness testimony

The authors explored the relevance of research on change blindness to eyewitness identification and testimony under intentional and incidental memory conditions. Participants (N = 80, 40 men and 40 women) viewed a video enactment of a burglary in which the identity of the burglar changed at the halfway point of the film. Half of participants were briefed to remember the content, and the other half were not. All were tested for the recall of the content, awareness of the change, and ability to identify either or both of the burglars. Some 61% of participants did not notice the identity change. Rates of detection were significantly higher in participants in the intentional condition, who also recalled significantly more detail from the film. Awareness of change was also significantly related to content recall scores and accuracy of identification of both burglars. The results illustrate the interrelation between the eyewitness and change blindness literatures.     

Auditory attention causes visual inattentional blindness

When engaged in a visual task, we can fail to detect unexpected events that would otherwise be very noticeable. Here we ask whether a common auditory task, such as that of attending to a verbal stream, can also make us blind to the presence of visual objects that we do not anticipate. In two experiments, one hundred and twenty observers watched a dynamic display while performing either a visual or an auditory attention task, or both simultaneously. When observers were listening to verbal material, in order to either understand it or to remember it (auditory task), their probability of detecting an unexpected visual object was no higher than when they were counting bounces of moving items (visual task), although in the former case the observers' eyes and attention could move around the display freely rather than remaining focused on tracked items. Previous research has shown that attending to verbal material does not affect responses to lights flashing at irregular intervals, suggesting that driving performance is not hampered by listening. The lights, however, were expected. Our data imply that listening to the radio while driving, or to a portable audio player while walking or biking, can impair our reactions to objects or events that we do not expect.     

Change blindness and the primacy of object appearance

A large body of work suggests that the visual system is particularly sensitive to the appearance of new objects. This is based partly on evidence from visual search studies showing that onsets capture attention whereas many other types of visual event do not. Recently, however, the notion that object onset has a special status in visual attention has been challenged. For instance, an object that looms toward an observer has also been shown to capture attention. In two experiments, we investigated whether onset receives processing priority over looming. Observers performed a change detection task in which one of the display objects either loomed or receded, or a new object appeared. Results showed that looming objects were more resistant to change blindness than receding objects. Crucially, however, the appearance of a new object was less susceptible to change blindness than both looming and receding. We argue that the visual system is particularly sensitive to object onsets.     

Perceptual, not memorial, disruption underlies emotion-induced blindness

Emotion-induced blindness refers to impaired awareness of stimuli appearing in the temporal wake of an emotionally arousing stimulus (S. B. Most, Chun, Widders, & Zald, 2005). In previous emotion-induced blindness experiments, participants withheld target responses until the end of a rapid stream of stimuli, even though each target appeared in the middle of the stream. The resulting interval between the targets' offset and participants' initiation of a response leaves open the possibility that emotion-induced blindness reflects a failure to encode or maintain target information in memory rather than a failure of perception. In the present study, participants engaged in a typical emotion-induced blindness task but initiated a response immediately upon seeing each target. Emotion-induced blindness was nevertheless robust. This suggests that emotion-induced blindness is not attributable to the delay between awareness of a target and the initiation of a response, but rather reflects the disruptive impact of emotional distractors on mechanisms driving conscious perception.     

Preserved visual representations despite change blindness in infants

Combining theoretical hypotheses of infant cognition and adult perception, we present evidence that infants can maintain visual representations despite their failure to detect a change. Infants under 12 months typically fail to notice a change to an object's height in a covering event. The present experiments demonstrated that 11‐month‐old infants can nevertheless maintain a viable representation of both the pre‐ and post‐change heights despite their ‘change blindness’. These results suggest that infants, like adults, can simultaneously maintain multiple representations, even if they do not optimally use them.     

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.     

Aftereffect of visual movement: Storage in the absence of a patterned surround

Storage of the visual movement aftereffect is shown to occur if, after movement, the stationary target remains clearly visible in a surround that is dark and featureless. This finding is considered in terms of the earlier observation that the movement aftereffect is reduced or eliminated when the target surround is featureless. It is noted that current hypotheses in terms of direction-specific units cannot easily explain the storage of the movement aftereffect.     

On the disruption of visual memory: Interference produced by visual report cues

Report of single letters from centrally-fixated, seven-letter, target rows was probed by either auditory or visual cues. The target rows were presented for 100 ms, and the report cues were single digits which indicated the spatial location of a letter. In three separate experiments, report was always better with the auditory cues. The advantage for the auditory cues was maintained both when target rows were masked by a patterned stimulus and when the auditory cues were presented 500 ms later than comparable visual cues. The results indicate that visual cues produce modality-specific interference which operates at a level of processing beyond iconic representation.     

Perception in the absence of attention: perceptual processing in the Roelofs effect during inattentional blindness

We present two experiments that examine sensory processing during conditions of inattentional blindness. A large rectangular frame that normally induces a Roelofs effect can go unreported due to inattentional blindness. Even when participants fail to report the frame, they mislocalize an attended target in a way consistent with having processed the frame. A more demanding visuospatial distractor task can increase inattentional blindness during conditions of divided attention, but has no effect on the spatial mislocalization illusion. Our results support theories that postulate a significant amount of perceptual processing in the absence of attention.     

Repetition blindness and illusory conjunctions: errors in binding visual types with visual tokens.

Repetition blindness (Kanwisher, 1986, 1987) has been defined as the failure to detect or recall repetitions of words presented in rapid serial visual presentation (RSVP). The experiments presented here suggest that repetition blindness (RB) is a more general visual phenomenon, and examine its relationship to feature integration theory (Treisman & Gelade, 1980). Experiment 1 shows RB for letters distributed through space, time, or both. Experiment 2 demonstrates RB for repeated colors in RSVP lists. In Experiments 3 and 4, RB was found for repeated letters and colors in spatial arrays. Experiment 5 provides evidence that the mental representations of discrete objects (called "visual tokens" here) that are necessary to detect visual repetitions (Kanwisher, 1987) are the same as the "object files" (Kahneman & Treisman, 1984) in which visual features are conjoined. In Experiment 6, repetition blindness for the second occurrence of a repeated letter resulted only when the first occurrence was attended to. The overall results suggest that a general dissociation between types and tokens in visual information processing can account for both repetition blindness and illusory conjunctions.     

The dark side of visual awareness in sport: Inattentional blindness in a real-world basketball task

Most research in the field of decision making in sports has focused on the bright side of visual attention and has not taken the dark side of visual awareness into account. Understanding the costs of such inattention should be complementary to the study of how attention facilitates perception. In the present study, we provide evidence for the existence of inattentional blindness (IB) in a real-world basketball setting among adults (Experiment 1). In Experiment 2, we found that players with hardly any basketball experience were more likely to experience IB in a real-world basketball setting, as compared with experienced athletes. Improving the ecological validity of the setting by enhancing the perception-action coupling (Experiment 3) and increasing task difficulty (Experiment 4) did not appear to affect the occurrence of IB among experienced athletes. IB can be considered a limitation of the visual system, but it also highlights a critical aspect of visual processing, which allows us to remain focused on the important aspects of the world. But as is shown in the present experiments, it is possible to induce an attentional set—for example, by sport-specific instructions—that leads to players’ missing important game-relevant information.     

Intact visual perceptual discrimination in humans in the absence of perirhinal cortex

While the role of the perirhinal cortex in declarative memory has been well established, it has been unclear whether the perirhinal cortex might serve an additional nonmnemonic role in visual perception. Evidence that the perirhinal cortex might be important for visual perception comes from a recent report that monkeys with perirhinal cortical lesions are impaired on difficult (but not on simple) visual discrimination tasks. We administered these same tasks to nine amnesic patients, including three severely impaired patients with complete damage to perirhinal cortex bilaterally (E.P., G.P., and G.T.). The patients performed all tasks as well as controls. We suggest that the function of perirhinal cortex as well as antero-lateral temporal cortex may differ between humans and monkeys.     

Discrimination of compound stimuli involving the presence or absence of a distinctive visual feature

Pigeons learned a free operant, go/no-go discrimination between stimuli produced by rapid alternation of different features on the response key. The 0 degrees -B compound consisted of a vertical black line on a white background (the 0 degrees feature) alternated with a blank white field (the B feature), with successive 0.75-sec feature on periods separated by 0.20-sec dark periods. Pecks at the alternating 0 degrees and B features were recorded separately. When pecks at the 0 degrees -B compound were reinforced and pecks at the B-B stimulus (repeated brief presentations of the B feature) were extinguished, the birds pecked more at the 0 degrees feature than at the B feature in the 0 degrees -B compound; subsequently, decremental line-tilt generalization gradients were obtained. When pecks at B-B were reinforced and pecks at 0 degrees -B were extinguished, the rate of pecking at the 0 degrees feature decreased to a low level much more rapidly than did the rate of pecking at the B feature in the 0 degrees -B compound; incremental line-tilt gradients were obtained. Following training with pecks at 0 degrees -B reinforced and pecks at 0 degrees -0 degrees extinguished, incremental line-tilt gradients were obtained, whereas the gradients were decremental following training with 0 degrees -0 degrees reinforced and 0 degrees -B extinguished.