The roles of encoding, retrieval, and awareness

Consciousness and Cognition, 2010

The goal of this study is to characterize observers' abilities to detect gradual changes and to explore putative dissociations between conscious experience of change and behavioral adaptation to a changing stimulus. We developed a new experimental paradigm in which, on each trial, participants were shown a dot pattern on the screen. Next, the pattern disappeared and participants had to reproduce it. In some conditions, the target pattern was incrementally rotated over successive trials and participants were either informed or not of this change. We analyzed both awareness of the changes and the dynamics of behavioral adaptation, in a way that makes it possible to assess both variability and accuracy as they change over time. Results indicate a dissociation between change awareness and behavioral adaptation to the changes, and support the notion that unconscious representations of visual stimuli are more precise and detailed than previously suggested. We discuss the implications of these results for theories of change detection. Crown steps of 1°of visual angle on each display, with each display separated from the next one by a brief blank screen (1500 ms). Participants were instructed to press a button if they had noticed the scene change. The results indicated that half of the participants remained unaware of the change up to a dramatic rotation of 48°. However, when a shift back to the original scene was produced after a cumulated rotation of 20°or 30°that had so far remained undetected, most subjects could then clearly see the change. Authors concluded that visual memory had been updated, albeit in the absence of awareness. Indeed, if visual memory had not been updated at all, participants would not have been able to detect the change when presented anew with the original display. These results clearly challenge the idea that change blindness arises from a failure to maintain relevant information in memory (see also, .

Current Directions in Psychological …, 2005

People often fail to notice large changes to visual scenes, a phenomenon now known as change blindness. The extent of change blindness in visual perception suggests limits on our capacity to encode, retain, and compare visual information from one glance to the next; our awareness of our visual surroundings is far more sparse than most people intuitively believe. These failures of awareness and the erroneous intuitions that often accompany them have both theoretical and practical ramifications. This article briefly summarizes the current state of research on change blindness and suggests future directions that promise to improve our understanding of scene perception and visual memory.

Psychologia, 2008

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.

Encyclopedia of Cognitive Science

This study examined the notion that visually fixating at a stimulus can help prevent change blindness from occurring and looks at change blindness blindness, a common metacognitive error shown by participants. 77 participants were randomly selected and assigned to different conditions. Experimental group had an extra task that they had to perform while attending to the video and the control group only had to watch the video. Participants in both conditions were required to fill out a questionnaire measuring their confidence levels to notice the change. Both conditions failed to detect changes with insignificant difference between the groups, even though the stimulus was visually fixated. Most participants overestimated their change detecting abilities, predicting in the questionnaire that they would notice the change, while in practice they did not. Thus an extra task in the experimental condition did not produce a cognitive overload leading to change blindness. Still participants failed to detect changes when the stimulus was fixated and failed to measure their change detecting abilities realistically.

Psychonomic Bulletin & Review, 2004

Neuropsychologia, 2011

Visual short-term memory (VSTM) capacity is often assessed using change detection tasks, and individual differences in performance have been shown to predict cognitive aptitudes across a range of domains in children and adults. We recently showed that intelligence correlates with an attentional component necessary for change detection rather than with memory capacity per se ). It remained unclear, however, whether different attentional strategies during change detection have most impact during the encoding or maintenance of information. Here we present recent findings from our laboratory supporting the hypothesis that attentional selection during encoding dominates individual differences in change detection measures of visual short-term memory.

Consciousness and Cognition, 2011

Wiley Interdisciplinary …, 2011

Change blindness is the failure to notice an obvious change. Inattentional blindness is the failure to notice the existence of an unexpected item. In each case, we fail to notice something that is clearly visible once we know to look for it. Despite similarities, each type of blindness has a unique background and distinct theoretical implications. Here, we discuss the central paradigms used to explore each phenomenon in a historical context. We also outline the central findings from each field and discuss their implications for visual perception and attention. In addition, we examine the impact of task and observer effects on both types of blindness as well as common pitfalls and confusions people make while studying these topics.

In a series of three experiments, we explored the nature of implicit representations in change blindness (CB). Using 3 x 3 letter arrays, we asked subjects (Ss) to locate changes in paired arrays separated by 80 ms ISIs, in which one, two or three letters of a row in the second array changed. In one testing version, a tone followed the second array, signaling a row for partial report (PR). In the other version, no PR was required. After Ss reported whether a change had been detected and the PR had been completed (if required), they were asked to identify a degraded letter trigram that was either novel, or from a previously shown row (repetition priming). Our findings indicate that when CB occurs, both the pre-change and post-change stimulus information primes despite its unavailability to consciousness. Surprisingly, findings also indicate that when change detection occurs only the post-change information primes.

Acta Psychologica, 2008

People often fail to detect a change between two visual scenes, a phenomenon referred to as change blindness. This study investigates how a post-change object's similarity to the pre-change object influences memory of the pre-change object and affects change detection. The results of Experiment 1 showed that similarity lowered detection sensitivity but did not affect the speed of identifying the pre-change object, suggesting that similarity between the pre-and post-change objects does not degrade the pre-change representation. Identification speed for the pre-change object was faster than naming the new object regardless of detection accuracy. Similarity also decreased detection sensitivity in Experiment 2 but improved the recognition of the pre-change object under both correct detection and detection failure. The similarity effect on recognition was greatly reduced when 20% of each pre-change stimulus was masked by random dots in Experiment 3. Together the results suggest that the level of pre-change representation under detection failure is equivalent to the level under correct detection and that the pre-change representation is almost complete. Similarity lowers detection sensitivity but improves explicit access in recognition. Dissociation arises between recognition and change detection as the two judgments rely on the match-to-mismatch signal and mismatch-to-match signal, respectively.

2006

The mismatch negativity is an event-related potential that represents a preattentive change detection process. The aim of this study was to determine whether the mismatch negativity was present during 'change blindness', a striking phenomenon in which surprisingly large changes in a complex scene are not seen when they occur during a blink or an eye movement. In this study, large orientation changes elicited a candidate mismatch negativity between 180 and 320 ms that appeared to be independent of participants' performance (uncued 76% correct, miscued 59% correct with chance performance at 50%). This negativity, however, disappeared in the miscued 'change blind' condition. In conclusion, the mismatch negativity does not appear to be present during change blindness suggesting that in complex scenes even large changes may not trigger preattentive change detection processes. NeuroReport17:1011^1015

Trends in Cognitive Sciences, 2005

Change blindness is the striking failure to see large changes that normally would be noticed easily. Over the past decade this phenomenon has greatly contributed to our understanding of attention, perception, and even consciousness. The surprising extent of change blindness explains its broad appeal, but its counterintuitive nature has also engendered confusions about the kinds of inferences that legitimately follow from it. Here we discuss the legitimate and the erroneous inferences that have been drawn, and offer a set of requirements to help separate them. In doing so, we clarify the genuine contributions of change blindness research to our understanding of visual perception and awareness, and provide a glimpse of some ways in which change blindness might shape future research.

Neuropsychologia, 2010

It is commonly accepted that right posterior parietal cortex (PPC) plays an important role in updating spatial representations, directing visuospatial attention, and planning actions. However, recent studies suggest that right PPC may also be involved in processes that are more closely associated with our visual awareness as its activation level positively correlates with successful conscious change detection (Beck, D.M., Rees, G., Frith, C.D., & Lavie, N. (2001). Neural correlates of change detection and change blindness. Nature Neuroscience, 4, 645-650.). Furthermore, disruption of its activity increases the occurrences of change blindness, thus suggesting a causal role for right PPC in change detection (Beck, D.M., Muggleton, N., Walsh, V., & Lavie, N. (2006). Right parietal cortex plays a critical role in change blindness. Cerebral Cortex, 16, 712-717.). In the context of a 1-shot change detection paradigm, we applied transcranial magnetic stimulation (TMS) during different time intervals to elucidate the temporally precise involvement of PPC in change detection. While subjects attempted to detect changes between two image sets separated by a brief time interval, TMS was applied either during the presentation of picture 1 when subjects were encoding and maintaining information into visual short-term memory, or picture 2 when subjects were retrieving information relating to picture 1 and comparing it to picture 2. Our results show that change blindness occurred more often when TMS was applied during the viewing of picture 1, which implies that right PPC plays a crucial role in the processes of encoding and maintaining information in visual short-term memory. In addition, since our stimuli did not involve changes in spatial locations, our findings also support previous studies suggesting that PPC may be involved in the processes of encoding non-spatial visual information (Todd, J.J. & Marois, R. (2004). Capacity limit of visual short-term memory in human posterior parietal cortex. Nature, 428, 751-754.).