Failures of retrieval and comparison constrain change detection in natural scenes

Verbal interference paradigms: A systematic review investigating the role of language in cognition

This paper presents a systematic review of the empirical literature that uses dual-task interference methods for investigating the on-line involvement of language in various cognitive tasks. In these studies, participants perform some primary task X putatively recruiting linguistic resources while also engaging in a secondary, concurrent task. If performance on the primary task decreases under interference, there is evidence for language involvement in the primary task. We assessed studies (N = 101) reporting at least one experiment with verbal interference and at least one control task (either primary or secondary). We excluded papers with an explicitly clinical, neurological, or developmental focus. The primary tasks identified include categorization, memory, mental arithmetic, motor control, reasoning (verbal and visuospatial), task switching, theory of mind, visual change, and visuospatial integration and wayfinding. Overall, the present review found that covert language is likely to play a facilitative role in memory and categorization when items to be remembered or categorized have readily available labels, when inner speech can act as a form of behavioral self-cuing (inhibitory control, task set reminders, verbal strategy), and when inner speech is plausibly useful as "workspace," for example, for mental arithmetic. There is less evidence for the role of covert language in cross-modal integration, reasoning relying on a high degree of visual detail or items low on nameability, and theory of mind. We discuss potential pitfalls and suggestions for streamlining and improving the methodology.

A major role for retrieval and/or comparison in the set-size effects of change detection

Set-size effects in change detection have been attributed to capacity limits in a variety of processes, including perception, memory encoding, memory storage, memory retrieval, comparison, and decision. In this study, we investigated the locus of the effect of increasing set size from 1 to 2. The task was to detect a 90 degree change in the orientation of 1 or 2 briefly presented Gabor patterns in noise. To measure purely attentional effects and not another phenomena, such as crowding, a precue was used to manipulate relevant set size while keeping the display constant. The locus of the capacity limit was determined by varying when observers were cued to a single relevant stimulus. To begin, we measured the baseline set-size effect for change detection. Next, a dual-task procedure and a 100% valid postcue was added to test for an effect of decision: This modification did not reliably change the set-size effects. In the critical experiments, a 100% valid cue was provided during the retention interval between displays, or only one stimulus was presented in the second display (local recognition). For both of these conditions, there was only a relatively small set-size effect. These results are consistent with the bulk of capacity limits being in memory retrieval or comparison and not in perception, memory encoding, or memory storage.

Knowledge guides attention to goal-relevant information in older adults

How does viewers’ knowledge guide their attention while they watch everyday events, how does it affect their memory, and does it change with age? Older adults have diminished episodic memory for everyday events, but intact semantic knowledge. Indeed, research suggests that older adults may rely on their semantic memory to offset impairments in episodic memory, and when relevant knowledge is lacking, older adults’ memory can suffer. Yet, the mechanism by which prior knowledge guides attentional selection when watching dynamic activity is unclear. To address this, we studied the influence of knowledge on attention and memory for everyday events in young and older adults by tracking their eyes while they watched videos. The videos depicted activities that older adults perform more frequently than young adults (balancing a checkbook, planting flowers) or activities that young adults perform more frequently than older adults (installing a printer, setting up a video game). Participants completed free recall, recognition, and order memory tests after each video. We found age-related memory deficits when older adults had little knowledge of the activities, but memory did not differ between age groups when older adults had relevant knowledge and experience with the activities. Critically, results showed that knowledge influenced where viewers fixated when watching the videos. Older adults fixated less goal-relevant information compared to young adults when watching young adult activities, but they fixated goal-relevant information similarly to young adults, when watching more older adult activities. Finally, results showed that fixating goal-relevant information predicted free recall of the everyday activities for both age groups. Thus, older adults may use relevant knowledge to more effectively infer the goals of actors, which guides their attention to goal-relevant actions, thus improving their episodic memory for everyday activities.

Catastrophic individuation failures in infancy: A new model and predictions

Comparison of infant findings from the physical-reasoning and object-individuation literatures reveals a contradictory picture. On the one hand, physical-reasoning results indicate that young infants can use featural information to guide their actions on objects and to detect interaction violations (when objects interact in ways that are not physically possible) as well as change violations (when objects spontaneously undergo featural changes that are not physically possible). On the other hand, object-individuation results indicate that young infants typically cannot use featural information to detect individuation violations (when the number of objects revealed at the end of an event is less than the number of objects introduced during the event). In this article, we attempt to reconcile these two bodies of research. In a new model of early individuation, we propose that two systems help infants individuate objects in physical events: the object-file and physical-reasoning systems. Under certain conditions, disagreements between the systems result in catastrophic individuation failures, leading infants to hold no expectation at all about how many objects are present. We report experiments with 9- to 11-month-old infants (N = 216) that tested predictions from the model. After two objects emerged in alternation from behind a screen, infants detected no violation when the screen was lowered to reveal no object. Similarly, after two objects emerged in alternation from inside a box, which was then shaken, infants detected no violation when the box remained silent, as though empty. We end with new directions, suggested by our model, for research on early object representations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

In search of the focus of attention in working memory: 13 years of the retro-cue effect

The concept of attention has a prominent place in cognitive psychology. Attention can be directed not only to perceptual information, but also to information in working memory (WM). Evidence for an internal focus of attention has come from the retro-cue effect: Performance in tests of visual WM is improved when attention is guided to the test-relevant contents of WM ahead of testing them. The retro-cue paradigm has served as a test bed to empirically investigate the functions and limits of the focus of attention in WM. In this article, we review the growing body of (behavioral) studies on the retro-cue effect. We evaluate the degrees of experimental support for six hypotheses about what causes the retro-cue effect: (1) Attention protects representations from decay, (2) attention prioritizes the selected WM contents for comparison with a probe display, (3) attended representations are strengthened in WM, (4) not-attended representations are removed from WM, (5) a retro-cue to the retrieval target provides a head start for its retrieval before decision making, and (6) attention protects the selected representation from perceptual interference. The extant evidence provides support for the last four of these hypotheses.

Dimension-based attention in visual short-term memory

We investigated how dimension-based attention influences visual short-term memory (VSTM). This was done through examining the effects of cueing a feature dimension in two perceptual comparison tasks (change detection and sameness detection). In both tasks, a memory array and a test array consisting of a number of colored shapes were presented successively, interleaved by a blank interstimulus interval (ISI). In Experiment 1 (change detection), the critical event was a feature change in one item across the memory and test arrays. In Experiment 2 (sameness detection), the critical event was the absence of a feature change in one item across the two arrays. Auditory cues indicated the feature dimension (color or shape) of the critical event with 80 % validity; the cues were presented either prior to the memory array, during the ISI, or simultaneously with the test array. In Experiment 1, the cue validity influenced sensitivity only when the cue was given at the earliest position; in Experiment 2, the cue validity influenced sensitivity at all three cue positions. We attributed the greater effectiveness of top-down guidance by cues in the sameness detection task to the more active nature of the comparison process required to detect sameness events (Hyun, Woodman, Vogel, Hollingworth, & Luck, Journal of Experimental Psychology: Human Perception and Performance, 35; 1140-1160, 2009).

Evidence for unlimited capacity processing of simple features in visual cortex

Performance in many visual tasks is impaired when observers attempt to divide spatial attention across multiple visual field locations. Correspondingly, neuronal response magnitudes in visual cortex are often reduced during divided compared with focused spatial attention. This suggests that early visual cortex is the site of capacity limits, where finite processing resources must be divided among attended stimuli. However, behavioral research demonstrates that not all visual tasks suffer such capacity limits: The costs of divided attention are minimal when the task and stimulus are simple, such as when searching for a target defined by orientation or contrast. To date, however, every neuroimaging study of divided attention has used more complex tasks and found large reductions in response magnitude. We bridged that gap by using functional magnetic resonance imaging to measure responses in the human visual cortex during simple feature detection. The first experiment used a visual search task: Observers detected a low-contrast Gabor patch within one or four potentially relevant locations. The second experiment used a dual-task design, in which observers made independent judgments of Gabor presence in patches of dynamic noise at two locations. In both experiments, blood-oxygen level-dependent (BOLD) signals in the retinotopic cortex were significantly lower for ignored than attended stimuli. However, when observers divided attention between multiple stimuli, BOLD signals were not reliably reduced and behavioral performance was unimpaired. These results suggest that processing of simple features in early visual cortex has unlimited capacity.

Infants Actively Construct and Update Their Representations of Physical Events: Evidence from Change Detection by 12-Month-Olds

The present research investigates the effects of top-down information on 12-month-olds’ representations of physical events, focusing on their ability to detect an object change across different events. Infants this age typically fail to detect height changes in events with tubes even though they successfully do so in events with covers. In Experiment  1, infants who saw a tube event in which objects did not interact successfully detected a change in an object’s height, suggesting that object interaction affects infants’ categorization of physical events. Experiments 2 and 3 examined the fine-grained process of event representation. In Experiment  2, infants detected the change in the tube event if they were led by pretest exposure to believe that the event was conducted with a cover. In Experiment  3, infants who initially believed so updated their representation if shown a tube before object interaction occurred (but not after). Together, these findings provide new evidence that infants, like older children and adults, actively construct physical events. Whether they notice a change depends on their existing knowledge and the current representation of the event.

Comparison and Representation Failures Both Cause Real-World Change Blindness

Change blindness (CB) occurs when people miss changes across views. Hypothetically, CB would occur if observers failed to represent information about the changing object, but CB would also occur if observers represented and failed to compare information across views, or represented only the pre- or post-change object. For a variety of reasons, previous studies have been unable to determine which of these alternatives contribute to CB in an incidental real-world setting. To address these ambiguities, we conducted two real-world experiments using stimuli that changed on only one feature and tested recognition memory for both the changing feature and a non-changing feature. Participants also provided confidence ratings on recognition responses, allowing us to test whether CB has multiple causes within a single task setting. The results suggest that, in a single real-world setting, CB can be caused by both a failure to represent and a failure to compare information across views.

Temporal and Spatial Predictability of an Irrelevant Event Differently Affect Detection and Memory of Items in a Visual Sequence

We examined how the temporal and spatial predictability of a task-irrelevant visual event affects the detection and memory of a visual item embedded in a continuously changing sequence. Participants observed 11 sequentially presented letters, during which a task-irrelevant visual event was either present or absent. Predictabilities of spatial location and temporal position of the event were controlled in 2 × 2 conditions. In the spatially predictable conditions, the event occurred at the same location within the stimulus sequence or at another location, while, in the spatially unpredictable conditions, it occurred at random locations. In the temporally predictable conditions, the event timing was fixed relative to the order of the letters, while in the temporally unpredictable condition; it could not be predicted from the letter order. Participants performed a working memory task and a target detection reaction time (RT) task. Memory accuracy was higher for a letter simultaneously presented at the same location as the event in the temporally unpredictable conditions, irrespective of the spatial predictability of the event. On the other hand, the detection RTs were only faster for a letter simultaneously presented at the same location as the event when the event was both temporally and spatially predictable. Thus, to facilitate ongoing detection processes, an event must be predictable both in space and time, while memory processes are enhanced by temporally unpredictable (i.e., surprising) events. Evidently, temporal predictability has differential effects on detection and memory of a visual item embedded in a sequence of images.

Change Detection in Visual Short-Term Memory: The Relative Impact of Pairwise Switches and Identity Substitutions

Numerous kinds of visual event challenge our ability to keep track of the objects that populate our visual environment from moment to moment. These include blinks, occlusion, shifting visual attention, and changes to object's visual and spatial properties over time. These visual events may lead to objects falling out of our visual awareness, but can also lead to unnoticed changes, such as undetected object replacements and positional exchanges. Current visual memory models do not predict which visual changes are likely to be the most difficult to detect. We examine the accuracy with which switches (where two objects exchange locations) and substitutions (where one or two objects are replaced) are detected. Inferior performance for one-object substitutions versus two-objects switches, along with superior performance for two-object substitutions versus two-object switches was found. Our results are interpreted in terms of object file theory, trade-offs between diffused and localized attention, and net visual change.

Eye movements, visual search and scene memory, in an immersive virtual environment

Visual memory has been demonstrated to play a role in both visual search and attentional prioritization in natural scenes. However, it has been studied predominantly in experimental paradigms using multiple two-dimensional images. Natural experience, however, entails prolonged immersion in a limited number of three-dimensional environments. The goal of the present experiment was to recreate circumstances comparable to natural visual experience in order to evaluate the role of scene memory in guiding eye movements in a natural environment. Subjects performed a continuous visual-search task within an immersive virtual-reality environment over three days. We found that, similar to two-dimensional contexts, viewers rapidly learn the location of objects in the environment over time, and use spatial memory to guide search. Incidental fixations did not provide obvious benefit to subsequent search, suggesting that semantic contextual cues may often be just as efficient, or that many incidentally fixated items are not held in memory in the absence of a specific task. On the third day of the experience in the environment, previous search items changed in color. These items were fixated upon with increased probability relative to control objects, suggesting that memory-guided prioritization (or Surprise) may be a robust mechanisms for attracting gaze to novel features of natural environments, in addition to task factors and simple spatial saliency.

Angular declination and the dynamic perception of egocentric distance

The extraction of the distance between an object and an observer is fast when angular declination is informative, as it is with targets placed on the ground. To what extent does angular declination drive performance when viewing time is limited? Participants judged target distances in a real-world environment with viewing durations ranging from 36-220 ms. An important role for angular declination was supported by experiments showing that the cue provides information about egocentric distance even on the very first glimpse, and that it supports a sensitive response to distance in the absence of other useful cues. Performance was better at 220-ms viewing durations than for briefer glimpses, suggesting that the perception of distance is dynamic even within the time frame of a typical eye fixation. Critically, performance in limited viewing trials was better when preceded by a 15-s preview of the room without a designated target. The results indicate that the perception of distance is powerfully shaped by memory from prior visual experience with the scene. A theoretical framework for the dynamic perception of distance is presented.

Neural mechanisms by which attention modulates the comparison of remembered and perceptual representations

Attention is important for effectively comparing incoming perceptual information with the contents of visual short-term memory (VSTM), such that any differences can be detected. However, how attentional mechanisms operate upon these comparison processes remains largely unknown. Here we investigate the underlying neural mechanisms by which attention modulates the comparisons between VSTM and perceptual representations using functional magnetic resonance imaging (fMRI). Participants performed a cued change detection task. Spatial cues were presented to orient their attention either to the location of an item in VSTM prior to its comparison (retro-cues), or simultaneously (simultaneous-cues) with the probe array. A no-cue condition was also included. When attention cannot be effectively deployed in advance (i.e. following the simultaneous-cues), we observed a distributed and extensive activation pattern in the prefrontal and parietal cortices in support of successful change detection. This was not the case when participants can deploy their attention in advance (i.e. following the retro-cues). The region-of-interest analyses confirmed that neural responses for successful change detection versus correct rejection in the visual and parietal regions were significantly different for simultaneous-cues compared to retro-cues. Importantly, we found enhanced functional connectivity between prefrontal and parietal cortices when detecting changes on the simultaneous-cue trials. Moreover, we demonstrated a close relationship between this functional connectivity and d′ scores. Together, our findings elucidate the attentional and neural mechanisms by which items held in VSTM are compared with incoming perceptual information.

Attention is required for maintenance of feature binding in visual working memory

Working memory and attention are intimately connected. However, understanding the relationship between the two is challenging. Currently, there is an important controversy about whether objects in working memory are maintained automatically or require resources that are also deployed for visual or auditory attention. Here we investigated the effects of loading attention resources on precision of visual working memory, specifically on correct maintenance of feature-bound objects, using a dual-task paradigm. Participants were presented with a memory array and were asked to remember either direction of motion of random dot kinematograms of different colour, or orientation of coloured bars. During the maintenance period, they performed a secondary visual or auditory task, with varying levels of load. Following a retention period, they adjusted a coloured probe to match either the motion direction or orientation of stimuli with the same colour in the memory array. This allowed us to examine the effects of an attention-demanding task performed during maintenance on precision of recall on the concurrent working memory task. Systematic increase in attention load during maintenance resulted in a significant decrease in overall working memory performance. Changes in overall performance were specifically accompanied by an increase in feature misbinding errors: erroneous reporting of nontarget motion or orientation. Thus in trials where attention resources were taxed, participants were more likely to respond with nontarget values rather than simply making random responses. Our findings suggest that resources used during attention-demanding visual or auditory tasks also contribute to maintaining feature-bound representations in visual working memory—but not necessarily other aspects of working memory.

Differential functioning of retrieval/comparison processing in detection of the presence and absence of change

Background

The phenomenon of change blindness may reflect the failure to detect the presence of change or the absence of change. Although performing the latter is considered more difficult than the former, the differential functioning of retrieval/comparison processing that leads to differences between the detection of the presence and the absence of change has not been clarified. This study aimed to fill this research gap by comparing performance in the detection of the presence and the absence of a change in one item among a set of items.

Methodology/Principal Findings

Twenty subjects performed two types of change detection tasks, the first task was detection of one changed item among a set of unchanged items (detection of the presence of a change) and the other was the detection of one unchanged item among a set of changed items (detection of the absence of a change). The ANOVA results for the percentage of correct responses and signal detection measurement of A’ values regarding change detection and the pattern of the results indicate that the subjects found (1) detection of the presence of change less difficult than detection of the absence of change (2), rejection of the presence of change less difficult than acceptance of the presence of change, and (3) rejection of the absence of change as difficult as acceptance of the absence of change.

Conclusions/Significance

Retrieval/comparison processing for the detection of the presence of change differs from that for the absence of change, likely because the retrieval/comparison process appears aimed at determining whether an item has changed but not whether an item appears the same as it had previously. This conclusion suggests the existence of an identification process that recognizes each item as the same as that observed previously that exists apart from the mechanism underlying retrieval/comparison processing.

The strategic retention of task-relevant objects in visual working memory

The serial and spatially extended nature of many real-world visual tasks suggests the need for control over the content of visual working memory (VWM). We examined the management of VWM in a task that required participants to prioritize individual objects for retention during scene viewing. There were 5 principal findings: (a) Strategic retention of task-relevant objects was effective and was dissociable from the current locus of visual attention; (b) strategic retention was implemented by protection from interference rather than by preferential encoding; (c) this prioritization was flexibly transferred to a new object as task demands changed; (d) no-longer-relevant items were efficiently eliminated from VWM; and (e) despite this level of control, attended and fixated objects were consolidated into VWM regardless of task relevance. These results are consistent with a model of VWM control in which each fixated object is automatically encoded into VWM, replacing a portion of the content in VWM. However, task-relevant objects can be selectively protected from replacement.

Are multiple visual short-term memory storages necessary to explain the retro-cue effect?

Recent research has shown that change detection performance is enhanced when, during the retention interval, attention is cued to the location of the upcoming test item. This retro-cue advantage has led some researchers to suggest that visual short-term memory (VSTM) is divided into a durable, limited-capacity storage and a more fragile, high-capacity storage. Consequently, performance is poor on the no-cue trials because fragile VSTM is overwritten by the test display and only durable VSTM is accessible under these conditions. In contrast, performance is improved in the retro-cue condition because attention keeps fragile VSTM accessible. The aim of the present study was to test the assumptions underlying this two-storage account. Participants were asked to encode an array of colors for a change detection task involving no-cue and retro-cue trials. A retro-cue advantage was found even when the cue was presented after a visual (Experiment 1) or a central (Experiment 2) interference. Furthermore, the magnitude of the interference was comparable between the no-cue and retro-cue trials. These data undermine the main empirical support for the two-storage account and suggest that the presence of a retro-cue benefit cannot be used to differentiate between different VSTM storages.

From distributed resources to limited slots in multiple-item working memory: a spiking network model with normalization

Recent behavioral studies have given rise to two contrasting models for limited working memory capacity: a "discrete-slot" model in which memory items are stored in a limited number of slots, and a "shared-resource" model in which the neural representation of items is distributed across a limited pool of resources. To elucidate the underlying neural processes, we investigated a continuous network model for working memory of an analog feature. Our model network fundamentally operates with a shared resource mechanism, and stimuli in cue arrays are encoded by a distributed neural population. On the other hand, the network dynamics and performance are also consistent with the discrete-slot model, because multiple objects are maintained by distinct localized population persistent activity patterns (bump attractors). We identified two phenomena of recurrent circuit dynamics that give rise to limited working memory capacity. As the working memory load increases, a localized persistent activity bump may either fade out (so the memory of the corresponding item is lost) or merge with another nearby bump (hence the resolution of mnemonic representation for the merged items becomes blurred). We identified specific dependences of these two phenomena on the strength and tuning of recurrent synaptic excitation, as well as network normalization: the overall population activity is invariant to set size and delay duration; therefore, a constant neural resource is shared by and dynamically allocated to the memorized items. We demonstrate that the model reproduces salient observations predicted by both discrete-slot and shared-resource models, and propose testable predictions of the merging phenomenon.

Iconic memory requires attention

Two experiments investigated whether attention plays a role in iconic memory, employing either a change detection paradigm (Experiment 1) or a partial-report paradigm (Experiment 2). In each experiment, attention was taxed during initial display presentation, focusing the manipulation on consolidation of information into iconic memory, prior to transfer into working memory. Observers were able to maintain high levels of performance (accuracy of change detection or categorization) even when concurrently performing an easy visual search task (low load). However, when the concurrent search was made difficult (high load), observers' performance dropped to almost chance levels, while search accuracy held at single-task levels. The effects of attentional load remained the same across paradigms. The results suggest that, without attention, participants consolidate in iconic memory only gross representations of the visual scene, information too impoverished for successful detection of perceptual change or categorization of features.

Efficient summary statistical representation when change localization fails

People are sensitive to the summary statistics of the visual world (e.g., average orientation/speed/facial expression). We readily derive this information from complex scenes, often without explicit awareness. Given the fundamental and ubiquitous nature of summary statistical representation, we tested whether this kind of information is subject to the attentional constraints imposed by change blindness. We show that information regarding the summary statistics of a scene is available despite limited conscious access. In a novel experiment, we found that while observers can suffer from change blindness (i.e., not localize where change occurred between two views of the same scene), observers could nevertheless accurately report changes in the summary statistics (or "gist") about the very same scene. In the experiment, observers saw two successively presented sets of 16 faces that varied in expression. Four of the faces in the first set changed from one emotional extreme (e.g., happy) to another (e.g., sad) in the second set. Observers performed poorly when asked to locate any of the faces that changed (change blindness). However, when asked about the ensemble (which set was happier, on average), observer performance remained high. Observers were sensitive to the average expression even when they failed to localize any specific object change. That is, even when observers could not locate the very faces driving the change in average expression between the two sets, they nonetheless derived a precise ensemble representation. Thus, the visual system may be optimized to process summary statistics in an efficient manner, allowing it to operate despite minimal conscious access to the information presented.

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.

Control of working memory content in schizophrenia

People with schizophrenia (PSZ) exhibit signs of reduced working memory (WM) capacity. However, this may reflect an impairment in managing its content, e.g. preventing irrelevant information from taking up available storage space, rather than a true capacity reduction. We tested the ability to eliminate and update WM content in 38 PSZ and 30 healthy control subjects (HCS). Images of real-world objects were presented consecutively, and a tone cued the item most likely to be tested for memory. On half the trials, randomly intermixed, a second tone occurred. Participants were informed that the item cued by the second tone was now the most likely to be tested, and the item cued by the first tone now the least likely, providing incentive to eliminate the first cued item from WM. Both HCS and PSZ displayed a robust performance advantage for cued items. Unexpectedly, PSZ more efficiently removed the no-longer-essential item from WM than HCS. The magnitude of the WM clearance of this first cued item correlated with memory performance for the newly prioritized second cued item in PSZ, indicating that it was adaptive. However, WM clearance was not associated with WM capacity, ruling out the need to budget limited resources as an explanation for greater clearance in PSZ. A robust correlation between WM clearance and poverty of speech in PSZ instead suggests that the propensity to rapidly clear non-essential information and minimize the number of items in WM may be the reflection of a negative symptom trait. This finding may reflect a more general tendency of PSZ to focus processing more narrowly than HCS.

Change blindness and inattentional blindness

Change blindness and inattentional blindness are both failures of visual awareness. 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. WIREs Cogni Sci 2011 2 529-546 DOI: 10.1002/wcs.130 For further resources related to this article, please visit the WIREs website.

Age-related decline of visual processing components in change detection

Previous research has suggested that an age-related decline in change detection may be due to older adults using a more conservative response criterion. However, this finding may reflect methodological limitations of the traditional change detection design, in which displays are presented continuously until a change is detected. Across 2 experiments, the authors assessed adult age differences in a version of change detection that required a response after each pair of pre- and postchange displays, thus reducing the potential contribution of response criterion. Older adults performed worse than younger adults, committing more errors and requiring a greater number of display cycles for correct detection. These age-related performance declines were substantially reduced after controlling statistically for elementary perceptual speed. Search strategy was largely similar for the 2 age groups, but perceptual speed was less successful in accounting for age-related variance in detectability when a more precise spatial localization of change was required (Experiment 2). Thus, the negative effect of aging in the present tasks lies in a reduction of detection efficiency due largely to processing speed, though some strategy-level effects may also contribute. (PsycINFO Database Record (c) 2010 APA, all rights reserved).

[Visual representation of natural scenes in flicker changes]

Coherence theory in scene perception (Rensink, 2002) assumes the retention of volatile object representations on which attention is not focused. On the other hand, visual memory theory in scene perception (Hollingworth & Henderson, 2002) assumes that robust object representations are retained. In this study, we hypothesized that the difference between these two theories is derived from the difference of the experimental tasks that they are based on. In order to verify this hypothesis, we examined the properties of visual representation by using a change detection and memory task in a flicker paradigm. We measured the representations when participants were instructed to search for a change in a scene, and compared them with the intentional memory representations. The visual representations were retained in visual long-term memory even in the flicker paradigm, and were as robust as the intentional memory representations. However, the results indicate that the representations are unavailable for explicitly localizing a scene change, but are available for answering the recognition test. This suggests that coherence theory and visual memory theory are compatible.

The advantage of a ground surface in the representation of visual scenes

The present study used change detection tasks to examine whether there is an advantage of a ground surface in representing visual scenes. In 6 experiments, a flicker paradigm (Experiments 1 through 4) or a one-shot paradigm (Experiments 5 and 6) was used to examine whether changes on a ground surface were easier to detect than changes on a ceiling surface. Overall, we found that: (1) there was an advantage in detecting changes on a ground surface or changes to objects on a ground surface; (2) this advantage was dependent on the presence of a coherent ground surface; (3) this advantage could propagate to objects connected to the ground surface through "nested" contact relations; (4) this advantage was mainly due to improved encoding rather than improved retrieval and comparison of the ground surface; and (5) this advantage was dependent on the presentation duration of the scene but not the number of objects presented in the scene. Together, these results suggest a unique role of the ground surface in organizing visual scenes.

Effects of Viewing Time, Fixations, and Viewing Strategies on Visual Memory for Briefly Presented Natural Objects

We investigated the impact of viewing time and fixations on visual memory for briefly presented natural objects. Participants saw a display of eight natural objects arranged in a circle and used a partial report procedure to assign one object to the position it previously occupied during stimulus presentation. At the longest viewing time of 7,000 ms or 10 fixations, memory performance was significantly higher than at the shorter times. This increase was accompanied by a primacy effect, suggesting a contribution of another memory component—for example, visual long-term memory (VLTM). We found a very limited beneficial effect of fixations on objects; fixated objects were only remembered better at the shortest viewing times. Our results revealed an intriguing difference between the use of a blocked versus an interleaved experimental design. When trial length was predictable, in the blocked design, target fixation durations increased with longer viewing times. When trial length was unpredictable, fixation durations stayed the same for all viewing lengths. Memory performance was not affected by this design manipulation, thus also supporting the idea that the number and duration of fixations are not closely coupled to memory performance.

Episodic Representation of Diagnostic and Non-Diagnostic Object Color

In three experiments, we investigated transsaccadic object file representations. In each experiment, participants moved their eyes from a central fixation cross to a saccade target located between two peripheral objects. During the saccade, this preview display was replaced with a target display containing a single object to be named. On trials in which the target identity matched one of the preview objects, its color either matched or did not match the previewed object color. The results indicated that color changes disrupt perceptual continuity, but only for the class of objects for which color is diagnostic of object identity. When the color is not integral to identifying an object (for example, when the object is a letter or an object without a characteristic color), object continuity is preserved regardless of changes to the object's color. These results suggest that object features that are important for defining the object are incorporated into its episodic representation. Furthermore, the results are consistent with previous work showing that the quality of a feature's representation determines its importance in preserving continuity.

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.

The comparison of visual working memory representations with perceptual inputs

The human visual system can notice differences between memories of previous visual inputs and perceptions of new visual inputs, but the comparison process that detects these differences has not been well characterized. In this study, the authors tested the hypothesis that differences between the memory of a stimulus array and the perception of a new array are detected in a manner that is analogous to the detection of simple features in visual search tasks. That is, just as the presence of a task-relevant feature in visual search can be detected in parallel, triggering a rapid shift of attention to the object containing the feature, the presence of a memory-percept difference along a task-relevant dimension can be detected in parallel, triggering a rapid shift of attention to the changed object. Supporting evidence was obtained in a series of experiments in which manual reaction times, saccadic reaction times, and event-related potential latencies were examined. However, these experiments also showed that a slow, limited-capacity process must occur before the observer can make a manual change detection response.

A dynamic neural field model of visual working memory and change detection

Efficient visually guided behavior depends on the ability to form, retain, and compare visual representations for objects that may be separated in space and time. This ability relies on a short-term form of memory known as visual working memory. Although a considerable body of research has begun to shed light on the neurocognitive systems subserving this form of memory, few theories have addressed these processes in an integrated, neurally plausible framework. We describe a layered neural architecture that implements encoding and maintenance, and links these processes to a plausible comparison process. In addition, the model makes the novel prediction that change detection will be enhanced when metrically similar features are remembered. Results from experiments probing memory for color and for orientation were consistent with this novel prediction. These findings place strong constraints on models addressing the nature of visual working memory and its underlying mechanisms.

Taking a new look at looking at nothing

A crucial question in cognitive science is how linguistic and visual information are integrated. Previous research has shown that eye movements to objects in the visual environment are locked to linguistic input. More surprisingly, listeners fixate on now-empty regions that had previously been occupied by relevant objects. This 'looking at nothing' phenomenon has been linked to the claim that the visual system constructs sparse representations of the external world and relies on saccades and fixations to extract information in a just-in-time manner. Our model provides a different explanation: based on recent work in visual cognition and memory, it assumes that the visual system creates and stores detailed internal memory representations, and that looking at nothing facilitates retrieval of those representations.

Is a pre-change object representation weakened under correct detection of a change?

We investigated whether a pre-change representation is inhibited or weakened under correct change detection. Two arrays of six objects were rapidly presented for change detection in three experiments. After detection, the perceptual identification of degraded stimuli was tested in Experiments 1 and 2. The weakening of a pre-change representation was not observed under correct detection. The repetition priming effect was observed for a pre-change object and the magnitude was equivalent to the effect for a post-change object. Under change blindness, repetition priming for a pre-change representation was observed when detection did not require report of location in Experiment 1 and was not observed when location was required to be reported in Experiment 2. The results of Experiment 3 showed that a pre-change representation was recognized at a higher rate under correct detection than under change blindness, reflecting a stronger rather than a weaker pre-change representation in the former context.

Task-specific modulation of memory for object features in natural scenes

The influence of visual tasks on short and long-term memory for visual features was investigated using a change-detection paradigm. Subjects completed 2 tasks: (a) describing objects in natural images, reporting a specific property of each object when a crosshair appeared above it, and (b) viewing a modified version of each scene, and detecting which of the previously described objects had changed. When tested over short delays (seconds), no task effects were found. Over longer delays (minutes) we found the describing task influenced what types of changes were detected in a variety of explicit and incidental memory experiments. Furthermore, we found surprisingly high performance in the incidental memory experiment, suggesting that simple tasks are sufficient to instill long-lasting visual memories.

Indirect assessment of visual working memory for simple and complex objects

Previous research has shown that visual search performance is modulated by the current contents in visual working memory (VWM), even when the contents of VWM are irrelevant to the search task. For example, visual search is faster when the target--rather than a distractor--is surrounded by a shape currently held in VWM. This study uses the modulation of visual search by VWM to investigate properties of VWM. Participants wereasked to remember the color or the shape of novel polygons whose "goodness" of figure varied according to Garner's (1962) rotation and reflection transformation principle. During the memory retention interval, participants searched for a tilted line among vertical lines embedded inside colored polygons. Search was faster when the target--rather than a distractor--was enclosed by the remembered polygons. The congruity effect diminished with increasing memory load and decreasing figure goodness. We conclude that congruity effects in visual search can indirectly assess VWM representation strength.

Age differences in what is viewed and remembered in complex conjunction search

Older and younger adults searched arrays of 12 unique real-world photographs for a specified object (e.g., a yellow drill) among distractors (e.g., yellow telephone, red drill, and green door). Eye-tracking data from 24 of 48 participants in each age group showed generally similar search patterns for the younger and older adults but there were some interesting differences. Older adults processed all the items in the arrays more slowly than the younger adults (e.g., they had longer fixation durations, gaze durations, and total times), but this difference was exaggerated for target items. We also found that older and younger adults differed in the sequence in which objects were searched, with younger adults fixating the target objects earlier in the trial than older adults. Despite the relatively longer fixation times on the targets (in comparison to the distractors) for older adults, a surprise visual recognition test revealed a sizeable age deficit for target memory but, importantly, no age differences for distractor memory.

Attentional filtering of transients allows for a recovery from change blindness

Previous reports suggest that introducing distracting visual transients during a change-detection task can result in change blindness. In four experiments, we found that presenting the distracting transients repeatedly prior to the change produces a recovery from change blindness. This recovery from change blindness is not due solely to low-level neural adaptation of transient detectors, but instead seems to be based on attentional filtering of the distracting transient signals. This attentional filtering can be object-based rather than location-based. In addition, we found that the ability to achieve this attentional filtering depends critically on presenting the to-be-ignored transient signals prior to the time of the change.