Visual Memory Representations Research Articles

Conceptual distinctiveness supports detailed visual long-term memory for real-world objects.

Humans have a massive capacity to store detailed information in visual long-term memory. The present studies explored the fidelity of these visual long-term memory representations and examined how conceptual and perceptual features of object categories support this capacity. Observers viewed 2,800 object images with a different number of exemplars presented from each category. At test, observers indicated which of 2 exemplars they had previously studied. Memory performance was high and remained quite high (82% accuracy) with 16 exemplars from a category in memory, demonstrating a large memory capacity for object exemplars. However, memory performance decreased as more exemplars were held in memory, implying systematic categorical interference. Object categories with conceptually distinctive exemplars showed less interference in memory as the number of exemplars increased. Interference in memory was not predicted by the perceptual distinctiveness of exemplars from an object category, though these perceptual measures predicted visual search rates for an object target among exemplars. These data provide evidence that observers' capacity to remember visual information in long-term memory depends more on conceptual structure than perceptual distinctiveness.

The high fidelity of scene representation in visual long-term memory

The high fidelity of scene representation in visual long-term memory

Category-specificity in visual object recognition

Are all categories of objects recognized in the same manner visually? Evidence from neuropsychology suggests they are not: some brain damaged patients are more impaired in recognizing natural objects than artefacts whereas others show the opposite impairment. Category-effects have also been demonstrated in neurologically intact subjects, but the findings are contradictory and there is no agreement as to why category-effects arise. This article presents a pre-semantic account of category-effects (PACE) in visual object recognition. PACE assumes two processing stages: shape configuration (the binding of shape elements into elaborate shape descriptions) and selection (among competing representations in visual long-term memory), which are held to be differentially affected by the structural similarity between objects. Drawing on evidence from clinical studies, experimental studies with neurologically intact subjects and functional imaging studies, it is argued that PACE can account for category-effects at both behavioural and neural levels in patients and neurologically intact subjects. The theory also accounts for the way in which category-effects are affected by different task parameters (the degree of perceptual differentiation called for), stimulus characteristics (whether stimuli are presented as silhouettes, full line-drawings, or fragmented forms), stimulus presentation (stimulus exposure duration and position) as well as interactions between these parameters.

Transsaccadic Scene Memory Revisited: A 'Theory of Visual Attention (TVA)' Based Approach to Recognition Memory and Confidence for Objects in Naturalistic Scenes.

The study presented here introduces a new approach to the investigation of transsaccadic memory for objects in naturalistic scenes. Participants were tested with a whole-report task from which — based on the theory of visual attention (TVA) - processing efficiency parameters were derived, namely visual short-term memory storage capacity and visual processing speed. By combining these processing efficiency parameters with transsaccadic memory data from a previous study, we were able to take a closer look at the contribution of visual short-term memory capacity and processing speed to the establishment of visual long-term memory representations during scene viewing. Results indicate that especially the VSTM storage capacity plays a major role in the generation of transsaccadic visual representations of naturalistic scenes.

Visual memory for natural scenes: Evidence from change detection and visual search

This paper reviews research examining the role of visual memory in scene perception and visual search. Recent theories in these literatures have held that coherent object representations in visual memory are fleeting, disintegrating upon the withdrawal of attention from an object. I discuss evidence demonstrating that, far from being transient, visual memory supports the accumulation of information from scores of individual objects in scenes, utilizing both visual short-term memory and visual long-term memory. In addition, I review evidence that memory for the spatial layout of a scene and memory for specific object positions can efficiently guide search within natural scenes.

Representations of apparent rotation

If perspective views of an object in two orientations are displayed in alternation, observers will experience the object rotating back and forth in three-dimensional space. Rotational motion is perceived even though only two views are displayed and each view is two-dimensional. The results of 5 experiments converge on the conclusion that the perception of apparent rotational motion produces representations in visual memory corresponding to the spatial structure of the object along its arc of rotation. These representations are view-dependent, preserving information about spatial structure from particular perspectives, but do not preserve low-level perceptual details of the stimulus.

The role of visual short-term memory in empty cell localization

Three experiments examined the visual memory representation supporting performance at long interstimulus intervals (ISIs) in an empty cell localization task. Two arrays of dots within a 4 x 4 grid were displayed briefly in succession. One grid cell did not contain a dot in either array, and the task was to localize the empty cell. In Experiment 1, we replicated previous findings of recovery to high levels of performance at long ISIs. In Experiment 2, we tested whether figural grouping in visual short-term memory (VSTM) supports long-ISI performance by manipulating the complexity of the array pattern. Pattern complexity had no effect on empty cell localization at 0-msec ISI, suggesting dependence on high-capacity visible persistence, but there was a large simple pattern advantage at long ISIs, suggesting dependence on figural grouping in VSTM. Experiment 3 demonstrated that participants typically remember the empty cells of the first array, and not the dots, for comparison with Array 2.

Effects of stimulus structure and target-distracter similarity on the development of visual memory representations in schizophrenia

Introduction. In a previous study (Silverstein, Bakshi, Chapman, & Nowlis, 1998a, Cognitive Neuropsychiatry) we demonstrated that while schizophrenia patients showed similar learning curves as nonpatient controls when determining whether a configural pattern of elements has been seen before or not, they did not demonstrate any learning curve with nonconfigural stimuli (in contrast to controls). Methodological limitations of that study, however, precluded generalisability of those effects.Methods. In the present study, therefore, different groups of schizophrenia patients (n = 18) and controls (n = 22) were administered a modified version of the familiarity judgement task used in Silverstein et al. (1998a). In the new version of the task: (1) the patterns that repeated were different for each participant; and (2) half of the nonrepeating patterns were configural and half were nonconfigural.Results. These indicated stronger perceptual learning effects for the configural compared to the nonconfigural patterns, and overall better performance and more pronounced learning effects for the control group.Conclusions. The data provide further evidence for a schizophrenia-related impairment in perceptual organisation and in the ability to develop memory representations for novel stimuli.

The dynamics of language-related brain images

s 149 types on amplitudes during the categorization task, reflecting access to letter representation in visual long-term memory. The influence of task features on latencies suggested a parallel versus cooperative processing across hemispheres relating to the discrimination and categorization tasks respectively. The differential engagement of components of a common network over time depending on task requirements emphasizes the role of cortical dynamics during cognitive processes. Priming effects in lexical decision tasks

Superior Performance of Blind Compared With Sighted Individuals on Bimanual Estimations of Object Size

Five preliminary experiments on sighted individuals revealed marked overestimation on an object size-estimation task using a bimanual response. These experiments ruled out the possibility that overestimation was due to the mode of visual presentation (whether two-dimensional or three-dimensional), the input modality (visual or kinesthetic), or the influence of other visual cues. The main experiment then investigated whether these distortions are due to visual experience by using a variant of the same task to test 24 blind and 24 sighted control participants. Remarkably, the sighted control participants overestimated object size, on average, but the blind participants did not. A follow-up experiment demonstrated that visual memory was the primary influence causing the size over-estimations. We conclude that blind individuals are more accurate than sighted individuals in representing the size of familiar objects because they rely on manual representations, which are less influenced by visual experience than are visual memory representations.

Working memory: imaging the magic number four.

Many brain regions have been implicated in memory performance, but the relationship between memory capacity and neural activity has not been clear. Recent studies show that activity in the posterior parietal cortex increases with working memory load, implicating this region in the storage of representations in visual memory.

Attention orienting and the time course of perceptual decisions: response time distributions with masked and unmasked displays

Mask-dependent cuing effects, like those previously found in yes–no detection, were found in a task in which observers judged the orientations of orthogonally-oriented Gabor patches presented at cued or uncued locations. Attentional cues enhanced sensitivity for masked, but not unmasked, stimuli. Responses were faster to cued than to uncued stimuli, irrespective of masking. The distributions of response times and accuracy were well described by a diffusion process model of decision making. Mask-dependent cuing was explained by an orienting model in which: (a) decisions are based on stable stimulus representations in visual short term memory that determine the rate of evidence accumulation in the diffusion process; (b) inattention delays the entry of stimuli into short term memory, and (c) masks limit the visual persistence of stimuli.

Perceptual completion and object-based representations in short-term visual memory.

Object-based representations in visual short-term memory (VSTM) were examined using a change detection memory task. A display comprising two rows of four differently colored elements was followed by a probe display in which only one of the rows reappeared. On same trials, the probed row was identical to the corresponding row in the memory display. On different trials, two of the elements in the probed row had their colors exchanged. In each memory display, a task-irrelevant visual element appeared between the two rows, with the potential to function as an occluder. Performance was enhanced when perceptual completion meant that four, rather than eight, objects were perceived in the memory display and when the probe display revealed that the occluded elements continued behind the occluder. It appears that several forms of representation can co-occur to support VSTM, one of which is object based.

The existence of internal visual memory representations

Although O'Regan & Noë (O&N) claim that the world may serve as the viewers' external visual memory, findings from the field of memory research have demonstrated the existence of internal visual representations. These representations are stored in the viewer's brain, contain information regarding visual objects and their relations, guide subsequent exploration of the visual world and promote change detection.

Contrast discrimination, non-uniform patterns and change blindness.

Change blindness--our inability to detect large changes in natural scenes when saccades, blinks and other transients interrupt visual input--seems to contradict psychophysical evidence for our exquisite sensitivity to contrast changes. Can the type of effects described as 'change blindness' be observed with simple, multi-element stimuli, amenable to psychophysical analysis? Such stimuli, composed of five mixed contrast elements, elicited a striking increase in contrast increment thresholds compared to those for an isolated element. Cue presentation prior to the stimulus substantially reduced thresholds, as for change blindness with natural scenes. On one hand, explanations for change blindness based on abstract and sketchy representations in short-term visual memory seem inappropriate for this low-level image property of contrast where there is ample evidence for exquisite performance on memory tasks. On the other hand, the highly increased thresholds for mixed contrast elements, and the decreased thresholds when a cue is present, argue against any simple early attentional or sensory explanation for change blindness. Thus, psychophysical results for very simple patterns cannot straightforwardly predict results even for the slightly more complicated patterns studied here.

Visual Imagery: Effects of Short- and Long-Term Memory

Visual imagery and perception share several functional properties and apparently share common underlying brain structures. A main approach to the scientific study of visual imagery is exploring the effects of mental imagery on perceptual processes. Previous studies have shown that visual imagery interferes with perception (Perky effect). Recently we have shown a direct facilitatory effect of visual imagery on visual perception. In an attempt to differentiate the conditions under which visual imagery interferes or facilitates visual perception, we designed new experimental paradigms, using detection tasks of a Gabor target. We found that imagery-induced interference and facilitation are memorydependent: Visual recall of common objects from long-term memory can interfere with perception, while on short-term memory tasks facilitation can be obtained. These results support the distinction between low-level and structural representations in visual memory.

Two types of representation in visual memory: Evidence from the effects of stimulus contrast on image combination

An imagery task was used to explore the distinction between visual memory representations that preserve surface features and more abstract descriptions. Subjects were shown two line drawings and were then asked to combine a visual image of each drawing in order to identify a novel figure. The main experimental manipulation concerned the contrast in which each drawing was shown, which was either normal or reversed. Experiment 1 showed that image combination was more efficient when the contrasts of the two drawings were congruent with each other, but only when the imagery task was performed under conditions emphasizing short-term memory (STM). There was no effect of congruity when one of the images was generated from long-term memory (LTM). These results are consistent with the idea that the surface characteristics of a stimulus are preserved in visual STM, but a more abstract description is stored in visual LTM. In Experiment 2 we explored the influence of verbal recoding on performance of the imagery task by requiring subjects to suppress articulation. Under LTM conditions, performance of the imagery task was improved by suppression and became sensitive to contrast congruity. Under STM conditions, imagery was unaffected by suppression. Overall, these results support the distinction between surface and abstract descriptions in visual memory. However, they suggest that this distinction does not map onto that between STM and LTM in any simple way. It is suggested that short-term visual memory maintains surface descriptions and long-term visual memory preserves both surface and abstract descriptions. Verbal coding of visual stimuli appears to encourage the use of abstract visual descriptions.

Memory for performed and imaged noun pairs and verb pairs

In a previous study by Engelkamp, cued recall of performed verb pairs was shown to be poorer than free recall of the same word pairs. For visually encoded verb pairs and for noun pairs, cued recall gave higher scores than free recall. This interaction between test types and encoding interactions was taken as support for the theory that motormemory representations differ from visual memory representations. With some modifications, the present experiment is an extension of one of Engelkamp's experiments. The subjects were given instructions that emphasized, more than those of Engelkamp, the integration aspect, and a further condition enacting noun pairs was added. Several parallel observations were made, but the crucial interaction between tests and encoding conditions was not replicated. The results are interpreted in terms of a problem-solving analysis.

The Role of Visual Image and Perception in Speech Development of Children With Speech Pathology

It is assumed that in children with various speech pathologies the naming function can be underdeveloped because of defects in the word's gnostic base. Our study revealed impairment in visual memory, perception, and visual representations of an object only in children with speech difficulties, whereas these functions were preserved in normal children of the same age. The children suffering from severe speech disorders (and particularly from naming difficulties) revealed more defects in visual perception and representations than in visual operational memory, which was grossly distorted in children with intellectual inadequacies. However, in this group, visual perception was impaired to a lesser degree. These results form the basis for methodological recommendations to begin rehabilitation of naming with development of the gnostic sphere.