Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SIZE PERCEPTION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73Linked to original sources
PubMed2004

The functional anatomy of inspection time: an event-related fMRI study.

Twenty healthy young adults underwent functional magnetic resonance imaging (fMRI) of the brain while performing a visual inspection time task. Inspection time is a forced-choice, two-alternative visual backward-masking task in which the subject is briefly shown two parallel vertical lines of markedly different lengths and must decide which is longer. As stimulus duration decreases, performance declines to chance levels. Individual differences in inspection time correlate with higher cognitive functions. An event-related design was used. The hemodynamic (blood oxygenation level-dependent; BOLD) response was computed as both a function of the eight levels of stimulus duration, from 6 ms (where performance is almost at chance) to 150 ms (where performance is nearly perfect), and a function of the behavioral responses. Random effects analysis showed that the difficulty of the visual discrimination was related to bilateral activation in the inferior fronto-opercular cortex, superior/medial frontal gyrus, and anterior cingulate gyrus, and bilateral deactivation in the posterior cingulate gyrus and precuneus. Examination of the time courses of BOLD responses showed that activation was related specifically to the more difficult, briefer stimuli and that deactivation was found across most stimulus levels. Functional connectivity suggested the existence of two networks. One comprised the fronto-opercular area, intrasylvian area, medial frontal gyrus, and the anterior cingulate cortex (ACC), possibly associated with processing of visually degraded percepts. A posterior network of sensory-related and associative regions might subserve processing of a visual discrimination task that has high processing demands and combines several fundamental cognitive domains. fMRI can thus reveal information about the neural correlates of mental events which occur over very short durations.

Adult↗
PubMed2005

Altering Mueller-Lyer illusion magnitude using figural additions at the wing-shaft intersections.

The Mueller-Lyer (ML) illusion has been used to study the way in which perceived length is affected by processes of information extraction when a visual target of interest (the ML shaft) is surrounded by other nontarget figural elements (inward-or outward-turning wings). It is argued that the perception of length is computed in terms of the center of gravity or centroid of figural elements at the wing-shaft intersection. The outward-turning wings shift the computational centroid away from the shaft end, giving rise to an erroneous overestimation of shaft length, while the inward-turning wings have the opposite effect. In three experiments, we observed that figural changes, which theoretically shifted the center of gravity of figural elements at the wing-shaft intersection, also increased or decreased the magnitude of the ML illusion.

Adolescent↗
PubMed2005

Perceptual adaptation affects attractiveness of female bodies.

We investigated whether short durations (5 minutes) of exposure to distorted bodies can change subsequent perceptions of attractiveness and normality. Participants rated 110 female bodies, varying in width, on either their attractiveness or normality before and after exposure to either extremely narrow (-50% of original width in Experiments 1 and 2) or extremely wide bodies (+50% of original width in Experiment 1, and +70% of original width in Experiment 2). In both experiments, the most attractive and most normal looking bodies became significantly and substantially narrower after exposure to narrow bodies. The most normal looking body changed significantly after exposure to wide bodies, but the most attractive body did not. These results show that perceptions of body attractiveness can be influenced by experience, but that there is an asymmetry between the effects of exposure to narrow and wide bodies. We consider a possible mechanism for this unexpected asymmetry, as well as possible implications for the effects of media exposure on body-image. The most attractive body shape was consistently narrower than the most normal looking body shape. Substantial changes in what looked normal were accompanied by congruent changes in what looked attractive, suggesting that a normal or average body shape may function as a reference point against which body attractiveness is judged.

Adolescent↗
PubMed1989

Macropsia, micropsia, and episodic illusions in Japanese adolescents.

The prevalence of episodic macropsia, micropsia, and distortions of time perception was examined by questionnaire in 3,224 high-school students aged 13 to 18 years. About 9% of the students reported having experienced one or more types of episodic illusion within the past 6 months. The prevalence of probable migraine was more than three times higher in students with episodic illusions than in those with no episodic illusions. Experiencing more than one type of illusion was found to be associated with probable migraine. Illusions appeared only during fever or while falling asleep in 25% of a subsample of 1,315 students.

Adolescent↗
PubMed1996

Selective perception by dynamic touch.

Perceiving the length of a rod by dynamic touch is tied to the inertia tensor Iij, a quantification of its resistance to rotational acceleration. Perception of the portion extending in front of the grasp has previously been ascribed to decomposing one component of Iij by attention. The tensorial nature of dynamic touch suggests that this ability must be anchored wholly in the tensor. Three experiments show that perceived partial length is a function of two components of the tensor, one tied primarily to magnitude and the other tied primarily to direction, whereas perceived whole length is a function of a magnitude component alone. Dynamic touch is characterized in terms of a haptic perceptual instrument that softly assembles to exploit Iij differently depending on the intention, producing 1:1 maps that are appropriately scaled for each intention.

Adult↗
PubMedDate not supplied

How important are changes in body weight for mass perception?

It is often assumed that weight judgements depend primarily on the effort experienced in lifting an object against a 1-G force. Changes in effort and in other weight-cues certainly alter apparent heaviness; but there is a tendency towards mass-constancy when such changes are unrelated to mass. Under water or altered G, both the observer's body and other objects change their effective weight: the change in the former probably provides a cue to the latter. Mass-constancy increases with opportunity for adaptation to the change, leaving a negative aftereffect on return to normal circumstances. The discrimination of weight or mass also deteriorates with sudden changes in arm weight, just as it does with other types of maladaptation and with a reduction in sensory cues. The relative importance of arm weight and other factors has not been precisely measured, but experiments in prolonged spaceflight should help to elucidate the issue.

Arm↗
PubMed2005

Microgenesis and ontogenesis of perceptual organization: evidence from global and local processing of hierarchical patterns.

In two experiments, visual search and speeded classification were used to study perception of hierarchical patterns among participants aged 5 to 23 years. Perception of global configurations of few-element patterns and local elements of many-element patterns showed large age-related improvements. Only minor age-related changes were observed in perception of global configurations of many-element patterns and local elements of few-element patterns. These results are consistent with prior microgenetic analyses using hierarchical patterns. On the one hand, the rapid and effortless grouping of many small elements and the individuation of few large elements both mature by age 5. In contrast, the time-consuming and effortful grouping of few large elements and the individuation of many small elements improve substantially with age, primarily between ages 5 and 10. These findings support the view that perceptual organization involves multiple processes that vary in time course, attentional demands, and developmental trajectories.

Adolescent↗
PubMed1986

Peripheral vision and the aetiology of child pedestrian accidents.

Three experiments examined whether age and sex differences in pedestrian accidents might be partly attributable to differences in the visual perception of peripheral stimuli. Primary schoolchildren and adults responded individually to the presentation of lights at retinal eccentricities of 2 degrees, 20 degrees and 40 degrees. Experiments 1 and 2 measured reaction times and Expt 3 measured subjects' expectations of foveal and peripheral events. There were no age or sex differences in expectations. Lights were detected fastest in the 20-40 degrees range. Movement times were not variable across eccentricities. As expected, adults' and 11-year-olds' detections were faster than eight- and six-year-olds'. A case is made for more problem-analytic and multi-theoretical research in the area of the child pedestrian accidents.

Accidents, Traffic↗
PubMed2006

Cue-invariant networks for figure and background processing in human visual cortex.

Lateral occipital cortical areas are involved in the perception of objects, but it is not clear how these areas interact with first tier visual areas. Using synthetic images portraying a simple texture-defined figure and an electrophysiological paradigm that allows us to monitor cortical responses to figure and background regions separately, we found distinct neuronal networks responsible for the processing of each region. The figure region of our displays was tagged with one temporal frequency (3.0 Hz) and the background region with another (3.6 Hz). Spectral analysis was used to separate the responses to the two regions during their simultaneous presentation. Distributed source reconstructions were made by using the minimum norm method, and cortical current density was measured in a set of visual areas defined on retinotopic and functional criteria with the use of functional magnetic resonance imaging. The results of the main experiments, combined with a set of control experiments, indicate that the figure region, but not the background, was routed preferentially to lateral cortex. A separate network extending from first tier through more dorsal areas responded preferentially to the background region. The figure-related responses were mostly invariant with respect to the texture types used to define the figure, did not depend on its spatial location or size, and mostly were unaffected by attentional instructions. Because of the emergent nature of a segmented figure in our displays, feedback from higher cortical areas is a likely candidate for the selection mechanism by which the figure region is routed to lateral occipital cortex.

Adult↗
PubMed2002

An examination of perceptual and cognitive set shifting tasks in acute anorexia nervosa and following recovery.

OBJECTIVES: People with anorexia nervosa have a broad spread of symptoms including disturbances in perception, cognition, emotions and behaviour. The aim of this study was to examine tests of executive function (in particular, perceptual and cognitive set shifting tasks) in patients with a current or past diagnosis of anorexia nervosa (AN). METHOD: 30 AN patients, 16 subjects recovered from anorexia nervosa (ANR) and 23 healthy controls were examined using tests of executive function (initiation tasks and perceptual and cognitive set shifting). RESULTS: The AN and ANR subjects had significantly higher perceptual and cognitive set shifting scores than the controls. CONCLUSIONS: Impaired executive function in terms of set shifting tasks could represent a vulnerability factor for AN.

Adult↗
PubMed2004

The effect of hemispatial neglect on the perception of centre.

Highly variable bisection performance in neglect patients has been attributed to an increased 'zone of indifference'. The indifference zone indicates the discrepancy between two line lengths which are judged as equal in length. Following this argumentation, the central area of a line should be expanded in neglect patients. The present two experiments investigated for the first time the expansion of the central area using a modified version of the Landmark Task. The location of a central or asymmetrical bisection mark on a horizontal line had to be judged (centre/left/right). In both experiments neglect patients, unlike healthy and patient controls, showed clear deficits in judging the location of the mark correctly and tended to judge asymmetrical marks of up to 4 cm as centrally positioned. The results are in agreement with and provide the first clear evidence of an enlarged perceptual zone of indifference in patients with hemispatial visual neglect.

Aged↗
PubMed1998

Inertial eigenvalues, rod density, and rod diameter in length perception by dynamic touch.

Four experiments addressed the relevance of the eigenvalues Ik of the inertia tensor for perceiving length by dynamic touch. Experiments 1-2 focused on the consequences of limiting variation in the minimum eigenvalue I3. Both revealed that perceived length is a function of Ik. Whether the contribution of I3 is detected, however, depends on the range of values that characterize a particular object set. Experiments 3-4 considered the relationship between an independent index of a rod's diameter, which does not affect Ik, and actual manipulation of a rod's diameter, which does affect Ik. Whereas the former appeared as satisfaction of implicit instructions to alter reports of perceived length, the latter entailed actual differences in perceived length in accordance with Ik. Results are discussed with respect to the links among actual length, perceived length, and Ik, as well as, in particular, how these links guarantee that perceived length is in the range of actual lengths.

Adult↗
PubMed1993

Frames of reference and distinctive figural characteristics affect shape perception.

In 4 experiments it was found that global frameworks and local distinctive figural characteristics influenced the perception of shape and of pointing. In Experiments 1 and 2, Ss were asked to mark the center of the middle figure in arrays of 3 aligned figures (either triangles or squares). Displacements of the center indicated a perceived deformation of the shapes. In Experiment 3, Ss were asked to adjust the height of triangles in arrays similar to those in Experiment 1. Height adjustments made along the axis of apparent pointing resulted in extents that were shorter than the height necessary to form equilateral triangles. In Experiment 4, stimuli were isosceles triangles in which the apparent distortion had been nulled; however, Ss continued to perceive them as pointing in a direction consistent with their alignment, and hence shape distortion cannot be the cause of pointing.

Adult↗
PubMed1994

Haptic perception of partial-rod lengths with the rod held stationary or wielded.

Three experiments on the haptic perception of partial-rod lengths are reported. The rods were gripped between the two ends and held horizontal. The subjects held the rods stationary; the distribution of mass of the segment in front of the hand was fixed, while the distribution of mass of the segment behind the hand was varied. Perceived forward length was found to be significantly affected by the distribution of mass of the backward segment. Similar results were obtained when the rods were wielded. The results indicated that partial-rod lengths are specified by functions of mechanical perturbations acting on the hand, and not by the breaking up of the first moment of mass or the moment of inertia of the rod by attention as suggested previously by others. The results are also discussed with respect to invariant detection and attention.

Adult↗
PubMed1985

Integration of stimulus dimensions in perception and memory: composition rules and psychophysical relations.

A series of five experiments used the method of magnitude estimation to assess how height and width are integrated in perceptual and in memorial judgments of area. Separate groups of subjects estimated the areas of perceived or remembered rectangles produced by a symmetrical 4 X 4 factorial design of height and width. Additional independent groups of observers made area judgments, based on special mixes of perceptual and memorial information referring to the height and width components of the to-be-judged rectangles. Both perceptual and memory data obeyed the bilinear interaction prediction of the normative multiplicative model. The relation between perceived and actual area as well as the relation between remembered and actual area could both be described by a compressive power function, with the exponent being reliably smaller for remembered than for perceived area. These results seem to imply a principle of integration rule invariance across perceptual and memorial estimates of a given set of stimuli, in conjunction with characteristically different valuation operations.

Adult↗
PubMed1994

Sensory assessment of fat content: effect of emulsion and subject characteristics.

This work examines some of the fundamental stimulus properties contributing to the perception and discrimination of fat content in foods. In an initial experiment, oil-in-water (O/W) emulsions were prepared with 0, 5, 10, ..., 40, 45, and 50% sunflower oil (SUN) and homogenized at pressures of 100 and 300 bar. These were rated for "fat content" and "smoothness" on 9-point category scales. There were significant effects of fat concentration and processing pressure. Higher pressures, associated with a decreased fat particle size/number ratio, generated a slightly enhanced perception of fat content. In a second experiment, O/W emulsions were prepared with 0, 12, 24, 36, and 48% fat at 100 and 300 bar, from two oils differing in fat saturation: SUN and Hycoa 5 (HY5, a highly saturated commercial cocoa butter substitute). The results indicate significant main and interactive effects of fat type and concentration, but no significant effect of processing pressure were seen in this experiment. HY5 emulsions had a substantially greater measured viscosity and were judged higher in fat content than those prepared from SUN, particularly at higher fat levels. Analyses indicate a significant independent contribution of fat concentration to perceived fat content, beyond increased viscosity. There were no consistent main or interactive effects of subject age or body composition on judgments of fat content.

Adolescent↗
PubMed1976

A discrepancy between two modes of haptic length perception.

This study investigated the possibility that systematic differences exist between the perceptions resulting from the use of two different heptic modes to know the same object. In each of three experiments 24 male and female college students chose visual comparison stimuli to match the length of haptically presented standard stimuli. In each experiment significantly smaller visual matches were made when the length of the haptic standard was perceived by holding it between the thumb and index finger than when the haptic standard was perceived by stroking it from end to end with the index finger. Experiment 1 established a significant difference (p less than .05) using a horizontal visual comparison. Experiment 2 replicated this effect (p less than .001) using vertical visual comparisons. Experiment 3 again replicated the effect (p less than .001) with visual comparisons and ruled out the possibility that the effect was due to the orientation of the haptic stimuli.

Female↗