True and false memory priming of perceptual closure problems in healthy older adults and older adults with Alzheimer's disease

OBJECTIVE

The present study set out to investigate whether false memories for pictures exhibit priming effects in older adult controls (OACs) and people with early onset Alzheimer's disease (AD). We conducted two studies to examine whether false memories for pictures had a priming effect on a perceptual closure task (PCT).

METHOD

In Experiment 1, OACs and people with early onset AD were presented with pictorial versions of the Deese/Rodiger-McDermott lists and took part in a recognition task. This followed with a PCT, where both groups were shown degraded pictures that became clearer over time and participants had to identify the picture as quickly as possible. In Experiment 2, we manipulated the modality-verbal versus pictorial in both the study phase and PCT phase.

RESULTS

Experiment 1 results indicated false memories for pictures did not serve as effective primes in the PCT. Experiment 2 results revealed pictorial false memories primed the PCT significantly slower than pictorial true memories in the visual PCT task, but the reverse finding was shown for the verbal PCT task. Finally, verbal false memories primed the verbal PCT reliably faster than true memories.

CONCLUSIONS

Our findings show when solving pictorial problems, for both older adults and people with AD false memories may not activate the appropriate representation in memory for solving a pictorial problems whereas actually presented items do. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

An Examination of Factor Structure of Rod-and-Frame Test and Embedded-Figures Test1

The scores of 93 male students on Rod-and-frame Test (RFT), Embedded-figures Test (EFT) and on 3 reference tests for each of 4 intellectual factors were correlated and factor analyzed. The hypothesis that 2 of J. P. Guilford's factors, Convergent Production of Figural Transformations and Cognition of Figural Systems, would explain the performance in RFT, whereas figural transformations alone would explain performance in EFT was rejected (p < 0.000). Instead, RFT defined a separate factor and EFT also loaded figural systems. RFT and EFT had quite different factor patterns and shared only 4 to 16% common variance.

Autocracy Bias in Informal Groups Under Need for Closure

Two experiments investigated the tendency of groups with members under high (vs. low) need for cognitive closure to develop an autocratic leadership structure in which some members dominate the discussion, constitute the “hubs” of communication, and influence the group more than other members. The first experiment found that high (vs. low) need for closure groups, as assessed via dispositional measure of the need for closure, manifested greater asymmetry of conversational floor control, such that members with autocratic interactional style were more conversationally dominant and influential than less autocratic members. The second experiment manipulated the need for closure via time pressure and utilized a social network analysis. Consistent with expectation, groups under time pressure (vs. no pressure) showed a greater asymmetry of participation, of centrality, and of prestige among the group members, such that the more focal members were perceived to exert the greater influence over the groups’ decisions.

Incomplete Figure Perception and Invisible Masking

The Gollin test (measuring recognition thresholds for fragmented line drawings of everyday objects and animals) has traditionally been regarded as a test of incomplete figure perception or ‘closure’, though there is a debate about how such closure is achieved. Here, figural incompleteness is considered to be the result of masking, such that absence of contour elements of a fragmented figure is the result of the influence of an ‘invisible’ mask. It is as though the figure is partly obscured by a mask having parameters identical to those of the background. This mask is ‘invisible’ only consciously, but for the early stages of visual processing it is real and has properties of multiplicative noise. Incomplete Gollin figures were modeled as the figure covered by the mask with randomly distributed transparent and opaque patches. We adjusted the statistical characteristics of the contour image and empty noise patches and processed those using spatial and spatial-frequency measures. Across 73 figures, despite inter-subject variability, mean recognition threshold was always approximately 15% of total contour in naive observers. Recognition worsened with increasing spectral similarity between the figure and the ‘invisible’ mask. Near threshold, the spectrum of the fragmented image was equally similar to that of the ‘invisible’ mask and complete image. The correlation between spectral parameters of figures at threshold and complete figures was greatest for figures that were most easily recognised. Across test sessions, thresholds reduced when either figure or mask parameters were familiar. We argue that recognition thresholds for Gollin stimuli in part reflect the extraction of signal from noise.

Aggregation and Unit Formation in the Perception of Moving Collinear Lines

The degree to which collinear lines are treated as a unit in resolving rotary motion in depth was investigated with the use of parallel projection to make direction of motion ambiguous. The proportion of time that the collinear lines appeared to rotate in the same direction was used as an index of their perceptual coherence. When the gap between the lines was small, there was strong grouping of the lines with respect to direction of motion as well as appearance of rigidity for the configuration. For larger gaps the grouping for direction of motion was maintained, but the lines appeared to have different axes of rotation leading to an appearance of nonrigidity. It is concluded that line elements can be aggregated for the resolution of certain properties without constituting a unit in any general sense.

Surface Assignment Modulates Object Formation for Visual Short-Term Memory

Recent results have suggested that the operational units of visual short-term memory (VSTM) are whole objects, rather than features or the total amount of information to be remembered. Here, for the first time, the influence of surface assignment on object formation for VSTM was investigated. The observers had to memorize the features of four briefly presented (300 ms) two-part objects, followed by a mask and a cue indicating which object to report on. The experiments contrasted whether there were any apparent depth differences between the two parts of each object, and whether observers had to report on only one or both features of the post-cued target object. Depth differences induced with stereoscopic disparity, and with a pictorial depth cue (simple interposition of object features), interfered strongly with performance when both features of an object needed to be memorized, but aided performance when only a single feature needed to be remembered. Furthermore, there was considerable within-feature interference consistent with some previous findings, but contradicting others. The potential implications for conceptions of VSTM are discussed in the light of two hypothesized stages: an early feature-based stage, as well as a higher-level object-based stage where the depth manipulations exert their effects. The results argue for a strong modulatory influence of surface assignment on object formation for a VSTM task.

Perturbing Line Pictures for Identification of Visual Features and Their Syntax

Experiments are reported in which line pictures were perturbed by omission or displacement of a combination of single pixels, fragments of lines, contours, and whole figures. Different effects of perturbation were expected by selectively violating visual syntactic rules or by impeding the contribution of certain feature detectors.

The deterioration of the perturbed picture was measured according to standard psychophysical methods by rating on a 5-point scale. Multivariate methods were used to single out the relative effects of perturbation by, respectively, a set of single pixels, line fragments, contours and whole figures.

Lines, as opposed to loose pixels, are clearly powerful descriptors of the pictures; contours or whole figures do not add significantly to what lines already describe. Different effects were observed if perturbations were dislocations rather than removals. Then contours and whole figures showed a typical disrupting effect compared to line fragments. These results have consequences for the development of a syntax of visual form perception. The perturbation method seems appropriate for identifying features or syntactic rules, although the results are dependent on a number of environmental and contextual factors.

The role of shape complexity in the detection of closed contours

The detection of contours in noise has been extensively studied, but the detection of closed contours, such as the boundaries of whole objects, has received relatively little attention. Closed contours pose substantial challenges not present in the simple (open) case, because they form the outlines of whole shapes and thus take on a range of potentially important configural properties. In this paper we consider the detection of closed contours in noise as a probabilistic decision problem. Previous work on open contours suggests that contour complexity, quantified as the negative log probability (Description Length, DL) of the contour under a suitably chosen statistical model, impairs contour detectability; more complex (statistically surprising) contours are harder to detect. In this study we extended this result to closed contours, developing a suitable probabilistic model of whole shapes that gives rise to several distinct though interrelated measures of shape complexity. We asked subjects to detect either natural shapes (Exp. 1) or experimentally manipulated shapes (Exp. 2) embedded in noise fields. We found systematic effects of global shape complexity on detection performance, demonstrating how aspects of global shape and form influence the basic process of object detection.

Visuo-spatial ability in individuals with Down syndrome: is it really a strength?

Down syndrome (DS) is associated with extreme difficulty in verbal skills and relatively better visuo-spatial skills. Indeed, visuo-spatial ability is often considered a strength in DS. However, it is not clear whether this strength is only relative to the poor verbal skills, or, more impressively, relative to cognitive ability in general. To answer this question, we conducted an extensive literature review of studies on visuo-spatial abilities in people with Down syndrome from January 1987 to May 2013. Based on a general taxonomy of spatial abilities patterned after Lohman, Pellegrino, Alderton, and Regian (1987) and Carroll (1993) and existing studies of DS, we included five different domains of spatial abilities - visuo-spatial memory, visuo-spatial construction, mental rotation, closure, and wayfinding. We evaluated a total of 49 studies including 127 different comparisons. Most comparisons involved a group with DS vs. a group with typical development matched on mental age and compared on a task measuring one of the five visuo-spatial abilities. Although further research is needed for firm conclusions on some visuo-spatial abilities, there was no evidence that visuo-spatial ability is a strength in DS relative to general cognitive ability. Rather, the review suggests an uneven profile of visuo-spatial abilities in DS in which some abilities are commensurate with general cognitive ability level, and others are below.

Using the virtual reality-cognitive rehabilitation approach to improve contextual processing in children with autism

BACKGROUND

This pilot study investigated the efficacy of a novel virtual reality-cognitive rehabilitation (VR-CR) intervention to improve contextual processing of objects in children with autism. Previous research supports that children with autism show deficits in contextual processing, as well as deficits in its elementary components: abstraction and cognitive flexibility.

METHODS

Four children with autism participated in a multiple-baseline, single-subject study. The children were taught how to see objects in context by reinforcing attention to pivotal contextual information.

RESULTS

All children demonstrated statistically significant improvements in contextual processing and cognitive flexibility. Mixed results were found on the control test and changes in context-related behaviours.

CONCLUSIONS

Larger-scale studies are warranted to determine the effectiveness and usability in comprehensive educational programs.

Renal volumes measured by 3-dimensional sonography in healthy fetuses from 20 to 40 weeks

OBJECTIVES

The purpose of this study was to establish reference values for fetal kidney volumes as a function of gestational age, estimated by 3-dimensional sonography using the Virtual Organ Computer-Aided Analysis (VOCAL) technique (GE Healthcare, Kretztechnik, Zipf, Austria).

METHODS

Volumes of right and left kidneys were assessed in 213 healthy fetuses by 3-dimensional sonography using the VOCAL technique. Inclusion criteria were healthy women with singleton pregnancies, unremarkable comprehensive fetal sonographic findings, well-known gestational age established by first-trimester sonography, and gestational ages between 20 and 40 weeks. Exclusion criteria were patients lost to follow-up and birth weight abnormalities. Each patient was scanned once during pregnancy. Regression analysis was used to calculate unified formulas.

RESULTS

The mathematical models calculated in the study were as follows: expected right kidney volume = exp[-1.01 + (0.12 × gestational age)]; and expected left kidney volume = exp[-0.90 + (0.12 × gestational age)]. No significant intraobserver or inter-observer variability was observed for the determined volumes.

CONCLUSIONS

Reference values for right and left fetal kidney volumes throughout gestation using the rotational technique (VOCAL) are described. The use of this technique might aid in further definition of gestational age kidney volume standards to help in defining variations from the norm.

Psychometric validation and normative data of a second Chinese version of the Hooper Visual Organization Test in children

The Hooper Visual Organization Test (HVOT) is a measure of visuosynthetic ability. Previously, the psychometric properties of the HVOT have been evaluated for Chinese-speaking children aged 5-11 years. This study reports development and further evidence of reliability and validity for a second version involving an extended age range of healthy children and children with developmental disabilities (DD) from 5 to 14 years of age. Rasch analysis revealed that after deletion of 6 items, a 24-item version conformed to a unidimensional scale. The test showed satisfactory internal consistency; 3-week test-retest coefficients all exceeded .85 for three DD subsamples. The second version was able to successfully differentiate between the three DD subgroups (attention-deficit hyperactivity disorder, autism spectrum disorders, and mental retardation) and the healthy control group, with correct classification rates ranging from 86.6% to 94.1%. Its construct validity was supported by expected correlations. Accordingly, age-based normative data were established as a basis for interpretation of performance. In sum, the second Chinese version of the HVOT has good psychometric properties and norms that are suited for use in clinical practice.

Attentional signatures of perception: multiple object tracking reveals the automaticity of contour interpolation

Multiple object tracking (MOT) is an attentional task wherein observers attempt to track multiple targets among moving distractors. Contour interpolation is a perceptual process that fills-in nonvisible edges on the basis of how surrounding edges (inducers) are spatiotemporally related. In five experiments, we explored the automaticity of interpolation through its influences on tracking. We found that (1) when the edges of targets and distractors jointly formed dynamic illusory or occluded contours, tracking accuracy worsened; (2) when interpolation bound all four targets together, performance improved; (3) when interpolation strength was weakened (by altering the size or relative orientation of inducing edges), tracking effects disappeared; and (4) real and interpolated contours influenced tracking comparably, except that real contours could more effectively shift attention toward distractors. These results suggest that interpolation's characteristics-and, in particular, its automaticity-can be revealed through its attentional influences or "signatures" within tracking. Our results also imply that relatively detailed object representations are formed in parallel, and that such representations can affect tracking when they become relevant to scene segmentation.

How does our search engine "see" the world? The case of amodal completion

This article illustrates a dissociation between the perceived attributes of an object and the ability of those attributes to guide the deployment of attention in visual search. Orientation is an attribute that guides search. Thus, a vertical line will "pop out" amid horizontal distractors. Amodal completion can create perceptually convincing oriented stimuli when two elements appear to form a complete object partially hidden behind an occluder. Previous work (e.g., Rensink & Enns, Vision Research, 38, 2489-2505, 1998) has shown a preattentive role for amodal completion in search tasks. Here, we show that orientation based on perceptually compelling amodal completion may fail to guide attention. The broader conclusion is that introspection is a poor guide to the capabilities of our internal search engine.

Do bantams (Gallus gallus domesticus) experience amodal completion? An analysis of visual search performance

Whereas many mammals (some primates and mice) experience amodal completion, previous data split for avian species. However, experimental procedures have been quite different among the species, and thus a direct comparison of various avian species in the same experimental situation is needed. We tested whether bantams (Gallus gallus domesticus) would complete partly occluded figures using a visual search task on the touch monitor, which was successfully used in our previous study with pigeons. First, we trained 3 participants to search for a notched red diamond (a target) among complete diamonds (distracters). Next, white squares accompanied each figure with a small gap of a fixed size. In test, the location of the accompanying white squares sometimes changed. In some trials, the white squares exactly covered, or "occluded," the notched portion of the target. Humans are known to have great difficulty in finding such targets due to "automatic" completion of the notched part. However, bantams met no such difficulty at all. This result and the demonstration by Forkman (1998) of hens' amodal completion of figures placed on a perspective background, suggest that the perspective cue may have an important role in amodal completion in this species.

Perceptual organization, phonological awareness, and reading comprehension in adults with and without learning disabilities

It is not clear from research whether, or to what extent, reading comprehension is impaired in adults who have learning disabilities (LD). The influence of perceptual organization (PO) and phonological awareness (PA) on reading comprehension was investigated. PO and PA are cognitive functions that have been examined in previous research for their roles in nonverbal LD and phonological dyslexia, respectively. Nonverbal tests of PO and non-reading tests of PA were administered to a sample of adults with postsecondary education. Approximately two thirds of the sample had previously been diagnosed as having LD. In a multiple regression analysis, tests of PO and PA were used to predict scores for tests of reading comprehension and mechanics. Despite the nonverbal nature of the perceptual organizational test stimuli, PO strongly predicted reading comprehension. Tests of PA predicted decoding and reading speed. Results were interpreted as supporting the hypothesis that integrative processes usually characterized as nonverbal were nonetheless used by readers with and without disabilities to understand text. The study's findings have implications for understanding the reading of adults with learning disabilities, and the nature of reading comprehension in general.

The serial process in visual search

The conditions for serial search are described. A multiple target search methodology (Thornton & Gilden, 2007) is used to home in on the simplest target/distractor contrast that effectively mandates a serial scheduling of attentional resources. It is found that serial search is required when (a) targets and distractors are mirror twins, and (b) when the search elements lack the Gestalt property of intrinsic orientation. The finding is put into the context of Feature Integration Theory (Treisman & Gelade, 1980) that first identified the occasions of serial search to be important to object perception and understanding.

Handedness and spatial ability: Differential patterns of relationships

The purpose of this exploratory study was to add to our understanding of hemispheric specialisation by examining the relationships between functional laterality (as measured by handedness, eyedness, earedness, and footedness) and spatial tests. A total of 55 males and 170 females were tested for laterality preferences and spatial test performance using a range of six spatial tests. There was a statistically significant relationship between each of the laterality measures employed, with handedness and footedness demonstrating the most robust association. Multiple regression analyses highlighted that once potential confounds were statistically controlled (age, sex, and other types of functional laterality), 3-D rotation/visualisation and speeded visual exploration task performance showed small, but significant, relations with a tendency towards left-handedness over right-handedness in total and secondary (two-handed) scale scores. Flexibility of closure performance was associated with a tendency towards left-handedness in the total and one-handed scale scores. Spatial location memory was the lone spatial ability relating with a tendency towards right-handedness. Overall, these findings offer new insights into the interplay of handedness with alternative measures of laterality as well as with spatial abilities.

Using monochromatic design views to avoid a premature fixation on design solutions

OBJECTIVE

This study investigates whether the availability of a monochromatic design view can prevent an early fixation on details during the preliminary stages of a design task.

BACKGROUND

Design students are trained to tentatively sketch the overall form of a design concept before attending to its details. Literature suggests that using multiple colors for sketching a concept causes a gestalt-like grouping phenomenon and influences designers to adopt a contrasting strategy of adding details before sketching the overall form. An empirical study was conducted to assess the validity of these findings.

METHOD

In the study, 20 participants, randomly assigned to two groups, were allowed to use multiple colors to sketch a design concept within a digital sketching environment. However, only the single-color group had the ability to view a sketch, as it would appear in monochrome.

RESULTS

Both groups parsed the design concepts into their basic components and used colors as a means of distinguishing one component from another. However, the single-color group added significantly more details than the first or the multicolor group after sketching the overall form.

CONCLUSION

Verbal reports suggest that the single-color group was able to avoid an early fixation on details because the single-color view eliminated the discontinuities induced by the variation in color and allowed the participants to attend to the overall form instead of the individual components.

APPLICATION

The current findings highlight the importance of providing a monochrome design view within a sketching environment to avoid an early fixation on a specific design solution.

An item analysis of Raven's Colored Progressive Matrices among participants with Down syndrome

Standardized tests are widely used in intellectual disability research, either as dependent or control variables. Yet, it is not certain that their items give rise to the same performance in various groups under study. In the present work, 48 participants with Down syndrome were matched on their raw score on Raven's Colored Progressive Matrices (RCPM) with 48 participants with intellectual disability of undifferentiated etiology and 48 typical children. An item analysis was then conducted using the transformed item difficulties method, a statistical approach designed to detect differential item functioning between groups. Results showed that the difficulty of items was highly similar for the three groups. It is concluded that RCPM can be used with considerable confidence in comparative studies including typical, Down syndrome and intellectually disabled participants of undifferentiated etiology. Some methodological implications of these findings are discussed.

Local vs. global approaches to reproducing the Rey Osterrieth Complex Figure by children, adolescents, and adults with high-functioning autism

Individuals with autism have an atypical pattern of visual processing. Various studies have provided evidence that individuals with autism perceive the details of stimuli before the gestalt, the reverse of the typical pattern of visual processing. This study used the Rey Osterreith Complex Figure (ROCF) task and an objective scoring system to examine local/global processing approaches to its reproduction in 37 individuals diagnosed with high-functioning autism (HFA) compared to 49 age-, IQ-, and gender-matched typically developing controls (TD). The sample was divided into children (aged 8-14 years) and adolescents/adults (aged 15-47 years) to assess age effects. Results showed no difference in overall performance on the ROCF between HFA and TD children. TD participants displayed improved organizational and planning skills with age and a shift to global processing approaches, but there were no differences in performance between children and adolescents/adults with HFA. There was no evidence of enhanced local processing in either HFA group. These findings suggest that HFA individuals with average IQ scores do not have the clinically demonstrable evidence of the enhanced local processing thought to reflect increased local brain connectivity in more severely autistic individuals. The deficient global processing of the HFA adults reflects dependence of performance on impaired strategic problem-solving abilities, which has been demonstrated to result from under development of neural connectivity between visuo-spatial and frontal brain regions in HFA adults.

Development of perceptual completion originates in information acquisition

Adults have little difficulty perceiving objects as complete despite occlusion, but newborn infants perceive moving partly occluded objects solely in terms of visible surfaces. The developmental mechanisms leading to perceptual completion have never been adequately explained. Here, the authors examine the potential contributions of oculomotor behavior and motion sensitivity to perceptual completion performance in individual infants. Young infants were presented with a center-occluded rod, moving back and forth against a textured background, to assess perceptual completion. Infants also participated in tasks to assess oculomotor scanning patterns and motion direction discrimination. Individual differences in perceptual completion performance were strongly correlated with scanning patterns but were unrelated to motion direction discrimination. The authors present a new model of development of perceptual completion that posits a critical role for targeted visual scanning, an early developing oculomotor action system.

Measuring stipple aesthetics in hand-drawn and computer-generated images

When people compare a computer-generated illustration to a hand-drawn illustration of the same object, they usually perceive differences. This seems to indicate that the two kinds of images follow different aesthetic principles. To explore and explain these differences, the authors compare texture stippling in hand-drawn and computer-generated illustrations, using image-processing analysis techniques.

The other-race effect develops during infancy: evidence of perceptual narrowing

Experience plays a crucial role in the development of face processing. In the study reported here, we investigated how faces observed within the visual environment affect the development of the face-processing system during the 1st year of life. We assessed 3-, 6-, and 9-month-old Caucasian infants' ability to discriminate faces within their own racial group and within three other-race groups (African, Middle Eastern, and Chinese). The 3-month-old infants demonstrated recognition in all conditions, the 6-month-old infants were able to recognize Caucasian and Chinese faces only, and the 9-month-old infants' recognition was restricted to own-race faces. The pattern of preferences indicates that the other-race effect is emerging by 6 months of age and is present at 9 months of age. The findings suggest that facial input from the infant's visual environment is crucial for shaping the face-processing system early in infancy, resulting in differential recognition accuracy for faces of different races in adulthood.

Recognition of objects displayed with incomplete sets of discrete boundary dots

Most extant theories of shape perception assume or assert that various contour attributes, and in particular, the orientation, curvature and linear extent of the contours provide essential object recognition cues. The present study examined this proposal using discrete dots that marked locations on the outer boundary of namable objects, providing shape-patterns similar to silhouettes. For each shape, the display initially provided only a sampling of the total number of dots in the boundary, and the number of dots was periodically increased until the participant named the object. There were three treatment conditions in which the initial display as well as the periodic increments consisted of continuous arrays (strings) of dots, randomly positioned dots, or evenly spaced dots. Analysis showed objects were recognized with the fewest percentage of dots with the evenly spaced condition, and participants needed the greatest percentage with the contiguous array condition. In many cases objects could be identified when very few evenly spaced dots were shown, thereby providing large spacing between the dots. It seems unlikely that known neural mechanisms could extract contour attributes, e.g., orientation, curvature, and linear extent, from such sparse stimulus patterns, which provides a challenge to the proposition that these are essential shape cues.

Monocular patching in subjects with right-hemisphere stroke affects perceptual-attentional bias

Monocular patching is a possible inexpensive treatment for spatial neglect. Previous studies were unpromising, but since neglect symptoms are heterogeneous, fractionating spatial bias may detect significant effects of patching. Poststroke, perceptual-attentional (PA) spatial bias, motor-intentional (MI) spatial bias, or both may occur. In this study, six poststroke subjects bisected lines while self-monitoring their performance via a camera/video apparatus. We dissociated PA and MI spatial bias by right-left reversing visual feedback in some trials. Subjects were tested with and without right and left eye patches. Patching did not affect group line-bisection error, but both right and left patches decreased individual subject PA spatial bias (p < 0.05). We detected no patching effect on individual subject MI spatial bias (significant patch side by bias interaction, p = 0.03). When we examined each subject's results separately, patching improved performance in subjects who had greater PA and MI spatial biases. We conclude that monocular patching may primarily affect poststroke PA spatial bias. Further studies on this intervention are needed.

Geometric determinants of shape segmentation: tests using segment identification

The geometric determinants of shape decomposition were studied using a performance-based method. Observers' identification of contour segments was shown to be systematically modulated by their curvature properties, and by the geometric properties of the enclosed region. Specifically, negative minima of contour curvature provided the best segment boundaries. Segments with negative-minima boundaries were identified with greater accuracy than those with positive maxima or inflection boundaries of comparable length. Additionally, segment identification was shown to be determined by contour length, the turning angle at part boundaries, and the width at the part's base (hence the part's protrusion). The results indicate that part decomposition is an automatic process. Moreover, this process is graded, i.e. parts are more strongly segmented, or more likely to be perceived, according to the strength of many geometric determinants.

The development of visual feature binding processes after visual deprivation in early infancy

Higher visual functions were investigated in patients treated for bilateral congenital cataracts in two experiments. Participants were asked to detect either real or illusory contours (Kanizsa squares in Experiment 1 or one of four different Kanizsa contours in Experiment 2) among distractor items. Compared to normally sighted participants matched for age, gender and education, cataract patients treated after the age of 5-6 months took relatively longer to detect Kanizsa figures (Experiments 1 and 2) and they had higher miss rates (Experiment 2). The present results suggest that the ability of visual feature binding depends on early visual input and is permanently impaired if patterned vision is prevented in early infancy for 5 months or more.

Pigeons' recognition of partially occluded objects depends on specific training experience

DiPietro et al (2002 Perception 31 1299-1312) reported a dramatic improvement in pigeons' recognition of partially occluded objects after the birds had been trained to recognize objects that were placed on top of another surface. Here, we investigated whether training with partially erased stimuli or with notched stimuli that had a thin gap between the object and another surface would similarly enhance pigeons' recognition of partially occluded objects. We found that erased training had no effect on the birds' recognition of partially occluded objects. Training pigeons to recognize notched objects improved their performance with the same objects when they were partially occluded; but this improvement did not transfer to novel objects, a result that DiPietro et al reported after on-top training. Together, the present results and those of DiPietro et al implicate prior experience as a key factor in pigeons' recognition of partially occluded objects. Training experiences which improve recognition of partially occluded objects may do so because they improve decomposition of complex two-dimensional scenes by pigeons into separate entities.

Automatic, stimulus-driven attentional capture by objecthood

In three experiments, we investigated whether the mere organization of some elements in the visual field by Gestalt factors into a coherent unit (an object), with no abrupt onset or any other unique transient, could attract attention automatically. Participants viewed a display of nine red and green elements, one of which was the target, and had to identify the target's color. On some trials, a subset of the elements was grouped by Gestalt factors (collinearity, closure, and symmetry) into an object. The object was task-irrelevant and unpredictive of the target. Performance on trials with an object present in the display was faster than performance on trials with no object for targets in the object area (a benefit) but slower for targets in a nonobject area (a cost). These findings demonstrate that an object by itself can capture attention automatically in a stimulus-driven manner, much as exogenous cues can.

Pigeons discriminate continuous versus discontinuous line segments

Three experiments examined various facets of the perception of continuous and discontinuous line segments in pigeons. Pigeons were presented with 2 straight lines that were interrupted by a gap. In some instances, the lines were the same angle and were positioned so that they appeared (to human observers) to form a continuous line. In other instances, the lines were different angles or the same angle but spatially misaligned. The birds were trained to classify each stimulus as continuous or discontinuous using a go/no-go procedure. A series of tests followed in which the birds received novel discontinuous displays made up of familiar line segments, continuous and discontinuous stimuli made up of novel line segments (novel straight lines or curved lines), and familiar displays in which the gap was covered with a gray square. Results from the tests indicated that 2 of the 3 pigeons had learned a continuous-discontinuous categorization and that they appeared to use the relationship between the 2 line segments in discriminating the displays.

The development of visual object recognition in school-age children

This study documents the age-dependent development of visual object recognition abilities in 115 children aged 6 to 11 years, using a battery of neuropsychological tests based on Marrs model (Efron test, Warringtons Figure-Ground Test, Street Completion Test, Poppelreuter-Ghent Test, a selection of stimuli from the Birmingham Object Recognition Battery, a series of color photographs of objects presented from unusual perspectives or illuminated in unusual ways). The results suggest a maturation of complex visual perceptual abilities, possibly related to the development of the cerebral processes involved in object recognition, and could be the starting point for future investigations of these skills in impaired populations.

The return of object-based attention: selection of multiple-region objects

Objects can control the focus of attention, allowing features on the same object to be selected more easily than features on different objects. In the present experiments, we investigated the perceptual processes that contribute to such object-based attentional effects. Previous research has demonstrated that object-based effects occur for single-region objects but not for multiple-region objects under some conditions (Experiment 1, Watson & Kramer, 1999). Such results are surprising, because most objects in natural scenes are composed of multiple regions. Previous findings could therefore limit the usefulness of an object-based selection mechanism. We explored the generality of these single-region selection results by manipulating the extent to which different (i.e., multiple) regions of a single object perceptually grouped together. Object-based attentional effects were attenuated when multiple regions did not group into a single perceptual object (Experiment 1). However, when multiple regions grouped together based on (1) edge continuation (Experiments 2 and 3) or (2) part and occlusion cues (Experiment 4), we observed object-based effects. Our results suggest that object-based attention is a robust process that can select multiple-region objects, provided the regions of such objects cohere on the basis of perceptual grouping cues.

Developmental trends in utilizing perceptual closure for grouping of shape: effects of spatial proximity and collinearity

In two experiments, visual search was used to study the grouping of shape on the basis of perceptual closure among participants 5-23 years of age. We first showed that young children, like adults, demonstrate an efficient search for a concave target among convex distractors for closed connected stimuli but an inefficient search for open stimuli. Reliable developmental differences, however, were observed in search for fragmented stimuli as a function of spatial proximity and collinearity between the closure-inducing fragments. When only closure was available, search for all the age groups was equally efficient for spatially close fragments and equally inefficient for spatially distant fragments. When closure and collinearity were available, search for spatially close fragments was equally efficient for all the age groups, but search for spatially distant fragments was inefficient for younger children and improved significantly between ages 5 and 10. These findings suggest that young children can utilize closure as efficiently as can adults for the grouping of shape for closed or nearly closed stimuli. When the closure-inducing fragments are spatially distant, only older children and adults, but not 5-year-olds, can utilize collinearity to enhance closure for the perceptual grouping of shape.

Visual completion and complexity of visual shape in children with pervasive developmental disorder

Much evidence has been gathered for differences in visual perceptual processing in individuals with Autistic Spectrum Disorder. The presence of the fundamental process of visual completion was tested in a group of children with Pervasive Developmental Disorder (PDD), as this requires perceptually integrating visual structure into wholes. In Experiment 1, it was investigated whether visual completion is present for simple partly occluded shapes in a group of children with PDD and a typically developing group. In Experiment 2, the presence of contextual influences in visual completion was investigated for the two groups. A total of 19 children with PDD and 28 controls who were matched for chronological age and IQ took part in two primed-matching tasks. For both groups, visual completion was present and for both groups, contextual influences were found to be dominant in this process. However, only for the group with PDD no priming effects (PEs) were found from less regular primes on congruent test pairs. The group with PDD did integrate visual information into wholes and did this in a contextually dependent way. However, for more complex shapes, visual completion is weaker for this group.

The Amsler chart: absence of evidence is not evidence of absence

Early detection of the onset or progression of macular disease is likely to become increasingly important as new treatment modalities are introduced. Current best practice involves issuing patients with an Amsler chart for daily or weekly observation with the instruction to attend for immediate assessment should any new distortion be perceived. However the sensitivity of Amsler charts in detecting macular disease can be less than 50%, implying that presentation may be delayed in over half of patients with advancing disease relying on the Amsler chart to detect progression. A likely explanation for this is the phenomenon of perceptual completion whereby regular objects are "filled-in" across the scotoma. Although alternative tests have been developed and shown to have greater sensitivity, at present no straightforward, cheap, home-based test of macular disease progression is available. The development of such a self-diagnostic tool should be a research priority.

Closure facilitates contour integration

Closed contours are often better perceived than those not fully enclosing an area, i.e., open contours. This facilitation of contour integration by closure, however, has been questioned arguing that in earlier studies closed contours were often "smoother" than open ones, because open contours usually had turning points. To solve this controversy, we compared detection performance for closed circles or ellipses of a higher curvature with open contours of a lower curvature neither having any turning points. Performance for circles and ellipses declined with increasing gap size and recovered only for contours with very low curvatures. Furthermore, performance increased with increasing number of contour elements and was better for smooth compared to S-shaped contours that change direction of curvature. Our results clearly demonstrate that closure improves contour detection, even though this advantage might be minor. The advantage of closed contours is maximal compared to open contours of similar curvature.

[Adaptation to central scotoma. Part II. Perceptual filling-in phenomenon]

The visual cortex may reorganize after occurrence of a scotoma. Different experimental studies have shown that there is an attempt to minimize the impact of the scotoma, the missing information being filled-in by surrounding information. The clinical consequences of this filling-in phenomenon have been extensively studied by Safran and co-workers. The present review summarizes the current literature on this phenomenon and its clinical consequences. Furthermore, the authors present their own experience with the filling-in phenomenon in patients with age-related macular degeneration. Their study shows that, with few exceptions, the phenomenon only occurs in patients with bilateral central scotoma, in their better eye.

Bayesian contour extrapolation: geometric determinants of good continuation

We investigated whether observers use rate of change of curvature in visually extrapolating contour shape. Arcs of Euler spirals with positive or negative rate of change of curvature gamma (hence linearly increasing or decreasing curvature) disappeared behind the straight-edge of a half-disk occluder. Observers adjusted the position and the orientation of a line probe around the curved portion of the occluder to optimize the percept of extrapolation. These paired measurements were obtained at multiple distances from the point of occlusion in order to map out the extended shape of visually extrapolated contours. An Euler-spiral model was fit to the extrapolation data corresponding to each inducing contour. Maximum-likelihood estimates of extrapolation rate of change of curvature gamma/\ were consistently found to be negative, indicating that visually extrapolated contours are characterized by decaying curvature, irrespective of whether inducer curvature is increasing or decreasing as it approaches the occluder. Moreover, extrapolation gamma/\ was found to exhibit no systematic dependence on inducer gamma. The results indicate that the visual system does not extrapolate rate of change of contour curvature. They support a Bayesian model of contour extrapolation, in which the decay in extrapolation curvature derives from an interaction between a likelihood bias to continue estimated contour curvature, and a prior bias to minimize contour curvature. Rate of change of curvature does not play a role.

Oscillatory priming and form complexity

Detection of a target grouping is expedited when the target display is preceded by presentation of an oscillating premask that includes priming elements presented intraphasically and below detection threshold at the display locations subsequently occupied by the target. Five experiments were performed to investigate how priming is affected by both the complexity and the geometry of prime/target forms. Experiment 1 showed that the subjective complexity of different polygons was coded in accord with an objective measure of form complexity. Experiments 2 and 3 revealed oscillatory priming to increase as a function of the subjective complexity of prime/target forms when those forms were regular and predictable. However, Experiments 4 and 5 showed that this relation did not hold when the prime/target forms were irregular and unpredictable. Taken together, it is argued that both subjective complexity and the Prägnanz quality of the prime/target forms come to determine the magnitude of priming. These results are discussed with reference to current physiological hypotheses regarding perceptual organization.

Who owns the contour of a visual hole?

Holes are useful in the study of shape, contour curvature, and border ownership. Several authors have suggested that holes have figural or quasi-figural status. I discuss three criteria to test the evidence that holes behave more like figures than like ground: (i) holes perceived as such; (ii) similar performance for holes and figures; (iii) different performance for holes and other ground regions. Using these criteria, I review the literature and conclude that holes do not have figural status in relation to border ownership. I also argue that holes are ideal stimuli to study figure-ground organisation.

Evidence for a dissociation of structural and semantic knowledge in dementia of the Alzheimer type (DAT)

Object recognition and naming deficits in dementia of the Alzheimer type (DAT) have typically been attributed to deficits in semantic processing, with only a few studies proposing loci of deficits other than semantic. One possible cause of DAT object recognition impairments could involve deficits in processing structural aspects of visually presented items. In this paper, we assess the performance of a group of mild DAT patients on two tasks of structural access, object decision, and the complete/incomplete task (based on part-whole matching task), as well as on a semantic probes task, designed to assess the patients' semantic knowledge of the same items for which structural knowledge had earlier been assessed. The DAT patients were substantially impaired in their performance on tasks of structural access. Further, no evidence for item-to-item consistency in the DAT patients' errors for the structural and semantic tasks was found, raising the possibility that structural and semantic knowledge may become differentially impaired in DAT.

Closure of salient regions determines search for a collinear target configuration

Grouping operations offer an effective mechanism by which to structure complex visual scenes. Among the various principles that support element integration, closure may be regarded as a main factor in shape extraction. In five experiments, we investigated the impact of grouping by closure on search for target configurations made up of collinearly arranged corner junctions. Systematic variations in the configuration of distractor elements were explored to investigate how the figural information of distractors interferes with target detection. The results showed no search interference for distractor configurations that were open forms. By contrast, distractors making up closed forms reduced the efficiency of search performance, indicating closure as a major contributor to form detection in multielement configurations. In conclusion, the effects reported may be considered to arise from mechanisms of unit formation that support the rapid extraction of salient regions to guide search.

Perceptual grouping in disorganized schizophrenia

This study evaluated visual perceptual grouping in schizophrenia to test the hypothesis that the disorganization syndrome in schizophrenia is related to a deficit in cognitive coordination. Perceptual grouping was examined with three psychophysically well-controlled tasks in patients with disorganized schizophrenia (n=11), non-disorganized schizophrenia (n=24), psychotic disorders other than schizophrenia (n=31) and non-psychotic psychiatric disorders (n=35). These measures assessed processing of both concurrent and preceding stimulus context. Deficits in perceptual grouping were observed on all three tasks in disorganized schizophrenia patients. Dysfunctional perceptual grouping mechanisms produced both enhanced and impaired task performance suggesting that the pattern of performance observed was the result of a specific deficit in the grouping of stimulus elements. We interpret these data as further support for the hypothesis that the disorganization syndrome in schizophrenia reflects a widespread deficit in the cognitive coordination of contextually related stimuli, leading to dysfunctional grouping of stimulus features in vision, thought and language.

Surface location and enclosure

This research addressed the issue of whether impressions of enclosure were more strongly influenced by amount of view covered by vertical boundaries (H1) or the presence of a boundary overhead (H2). There were three studies with totals of 48 stimuli and 142 respondents. Stimuli were balconies, swamps, and space stations. Effect sizes were reported for variables of boundaries below, in front of, and at the observers' sides, as well as amount of view covered by any boundary regardless of location with respect to the observer. Judged enclosure correlated at r =.80 for amount of view covered by vertical boundaries and r =.42 with the presence or absence of boundaries overhead, indicating that enclosure is more strongly related to vertical rather than overhead boundaries (alpha< .001).

Influences on cognitive engagement: epistemological beliefs and need for closure

BACKGROUND

Research indicates that achievement goals influence cognitive engagement, which, in turn, influences academic achievement. We believe that there are other individual difference variables in the realm of personal epistemology that may also directly or indirectly influence cognitive engagement; specifically, epistemological beliefs and epistemological motives (e.g. need for closure).

AIMS

This study proposed and tested a conceptual model of relationships among epistemological variables (epistemological beliefs and need for closure), achievement goals (mastery, performance-approach, performance-avoidance) and cognitive engagement.

SAMPLE

Two hundred and fifty-nine students attending university in the US volunteered to participate in the study. Students represented a variety of academic disciplines and ranged from 18 to 58 years.

METHODS

The participants completed three paper-and-pencil surveys: the Epistemological Beliefs Inventory; the Attitudes, Beliefs, and Experiences Inventory (a measure of need for closure); and the Approaches to Learning Survey (a measure of achievement goals and cognitive engagement).

RESULTS

Structural equation modelling supported the model in general, although not all proposed paths were significant. Correlational analyses further indicated that epistemological beliefs and need for closure are both potentially important variables for understanding learners' treatment of knowledge in instructional settings.

CONCLUSIONS

There are individual differences in epistemological beliefs and motives that may influence the goals students pursue in learning settings and the nature of their cognitive engagement.

Disappearance of memory fragments in patients with Alzheimer's disease: evidence from a longitudinal study of visual priming

Previous studies suggested that perceptual memory as indexed by visual priming is normal in patients with Alzheimer's disease (AD). However, these studies did not specifically test the long-term effects of visual priming, which may differ significantly between Alzheimer's patients and normal subjects. To test this possibility, we examined long-term visual priming in AD patients, 1 hour, 1 month, and 3 months after training. Our results indicated a significant difference in visual priming between AD patients and normal subjects after 3 months, but not 1 month. For AD patients, there was a strong positive correlation between the 3-month priming effect and the Mini-Mental State Examination (MMSE) scores-severely demented patients were less likely to exhibit priming after 3 months. It appears that severe cortical degeneration may render AD patients unable to consolidate their perceptual memories. Our results suggest that lack of visual priming in AD patients is linked to the inability to maintain fragmented perceptual memories.

Gestalt perception and local-global processing in high-functioning autism

This study examined gestalt perception in high-functioning autism (HFA) and its relation to tasks indicative of local visual processing. Data on of gestalt perception, visual illusions (VI), hierarchical letters (HL), Block Design (BD) and the Embedded Figures Test (EFT) were collected in adult males with HFA, schizophrenia, depression and normative controls. Individuals with HFA processed gestalt stimuli less in accord with gestalt laws, particularly regarding the principle of similarity. Gestalt processing correlated positively with global processing of the HL. EFT and BD performance correlated negatively with VI susceptibility in HFA. All clinical groups succumbed less to VI than the normative sample. Results suggest decreased gestalt perception in HFA, being associated with a more general local visual processing bias.