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PubMed1999

Visual perception of motion, luminance and colour in a human hemianope.

Human patients rendered cortically blind by lesions to V1 can nevertheless discriminate between visual stimuli presented to their blind fields. Experimental evidence suggests that two response modes are involved. Patients are either unaware or aware of the visual stimuli, which they are able to discriminate. However, under both conditions patients insist that they do not see. We investigate the fundamental difference between percepts derived for the normal and affected hemifield in a human hemianope with visual stimuli of which he was aware. The psychophysical experiments we employed required the patient, GY, to make comparisons between stimuli presented in his affected and normal hemifields. The subject discriminated between, and was allowed to match, the stimuli. Our study reveals that the stimulus parameters of colour and motion can be discriminated and matched between the normal and blind hemifields, whereas brightness cannot. We provide evidence for associations between the percepts of colour and motion, but a dissociation between the percepts of brightness, derived from the normal and hemianopic fields. Our results are consistent with the proposal that the perception of different stimulus attributes is expressed in activity of functionally segregated visual areas of the brain. We also believe our results explain the patient's insistence that he does not see stimuli, but can discriminate between them with awareness.

Adult↗

PubMed2005

Audiovisual speech perception in elderly cochlear implant recipients.

OBJECTIVES/HYPOTHESIS: This study examined the speech perception skills of a younger and older group of cochlear implant recipients to determine the benefit that auditory and visual information provides for speech understanding. STUDY DESIGN: Retrospective review. METHODS: Pre- and postimplantation speech perception scores from the Consonant-Nucleus-Consonant (CNC), the Hearing In Noise sentence Test (HINT), and the City University of New York (CUNY) tests were analyzed for 34 postlingually deafened adult cochlear implant recipients. Half were elderly (i.e., >65 y old) and other half were middle aged (i.e., 39-53 y old). The CNC and HINT tests were administered using auditory-only presentation; the CUNY test was administered using auditory-only, vision-only, and audiovisual presentation conditions RESULTS: No differences were observed between the two age groups on the CNC and HINT tests. For a subset of individuals tested with the CUNY sentences, we found that the preimplantation speechreading scores of the younger group correlated negatively with auditory-only postimplant performance. Additionally, older individuals demonstrated a greater reliance on the integration of auditory and visual information to understand sentences than did the younger group CONCLUSIONS: On average, the auditory-only speech perception performance of older cochlear implant recipients was similar to the performance of younger adults. However, variability in speech perception abilities was observed within and between both age groups. Differences in speechreading skills between the younger and older individuals suggest that visual speech information is processed in a different manner for elderly individuals than it is for younger adult cochlear implant recipients.

Adult↗

PubMed2003

Perception of plane orientation from self-generated and passively observed optic flow.

We investigated the perception of three-dimensional plane orientation--focusing on the perception of tilt--from optic flow generated by the observer's active movement around a simulated stationary object, and compared the performance to that of an immobile observer receiving a replay of the same optic flow. We found that perception of plane orientation is more precise in the active than in the immobile case. In particular, in the case of the immobile observer, the presence of shear in optic flow drastically diminishes the precision of tilt perception, whereas in the active observer, this decrease in performance is greatly reduced. The difference between active and immobile observers appears to be due to random rather than systematic errors. Furthermore, perceived slant is better correlated with simulated slant in the active observer. We conclude with a discussion of various theoretical explanations for our results.

Adult↗

PubMed2006

Adaptation aftereffects in the perception of gender from biological motion.

Human visual perception is highly adaptive. While this has been known and studied for a long time in domains such as color vision, motion perception, or the processing of spatial frequency, a number of more recent studies have shown that adaptation and adaptation aftereffects also occur in high-level visual domains like shape perception and face recognition. Here, we present data that demonstrate a pronounced aftereffect in response to adaptation to the perceived gender of biological motion point-light walkers. A walker that is perceived to be ambiguous in gender under neutral adaptation appears to be male after adaptation with an exaggerated female walker and female after adaptation with an exaggerated male walker. We discuss this adaptation aftereffect as a tool to characterize and probe the mechanisms underlying biological motion perception.

Adaptation, Physiological↗

PubMed1989

Auditory, visual, and multisensory nonverbal social perception in adolescents with and without learning disabilities.

Adolescents with and without learning disabilities (14, 16, and 18 years old) were tested to determine whether they differed in auditory, visual, and/or multisensory (combined auditory/visual) social perception abilities. Differences between the two groups in growth of auditory, visual, and multisensory social-perception abilities were also measured. Results of the data analyses revealed that adolescents with learning disabilities were not as adept at understanding nonverbal social information regardless of whether the information was visual or multisensory in nature. Further, nonverbal social-perception ability for both visual and multisensory information improved with increasing age for both populations. Finally, adolescents with learning disabilities continued to demonstrate comparatively poorer social-perception abilities through the 18-year level.

Adolescent↗

PubMed2006

Effects of the orientation of moving objects on the perception of streaming/bouncing motion displays.

In this study, we examined the contribution of the orientation of moving objects to perception of a streaming/bouncing motion display. In three experiments, participants reported which of the two types of motion, streaming or bouncing, they perceived. The following independent variables were used: orientation differences between Gabor micropatterns (Gabors) and their path of motion (all the experiments) and the presence/absence of a transient tone (Experiment 1), transient visual flash (Experiment 2), or concurrent secondary task (Experiment 3) at the coincidence of Gabors. The results showed that the events at coincidence generally biased responses toward the perception of bouncing. On the other hand, alignment of Gabors with their motion axes significantly reduced the frequency of bounce perception. The results also indicated that an object whose orientation was parallel to its motion path strengthened the spatiotemporal integration of local motion signals along a straight motion path, resulting in the perception of streaming. We suggest that the effect of collinearity between Gabors and their motion path is relatively free from the effect of attention distraction.

Humans↗

PubMed2006

Perception of biological motion from limited-lifetime stimuli.

The visual perception of human movement from sparse point-light walkers is often believed to rely on local motion analysis. We investigated the role of local motion in the perception of human walking, viewed from the side, in different tasks. The motion signal was manipulated by varying point lifetime. We found the task of coherence discrimination, commonly used in biological motion studies, to be inappropriate for testing the role of motion. A task requiring temporal information showed a strong performance drop when fewer points were used or when the image sequence was sampled and displayed at a reduced frame rate. Irrespective of the frame rate, performance did not vary with point lifetime. We concluded that local motion is not required for the perception of tested biological movements, suggesting that the analysis of biological motion does not benefit from examining local motion. The reliance of perception on the number of displayed points and frames supports the idea that biological motion is perceived from a sequence of spatiotemporally sampled forms.

Child↗

PubMed2004

[Anisotropy in depth perception of photograph].

How can we reproduce real physical depth from a photograph? How does depth perception in the photograph differ from depth perception in the direct observation? In Experiment 1, objects in an open space were photographed and presented on a screen. Subjects were asked to judge the distances from a fixed point to the objects and the angles from the median line. The distances and the angles in the photograph were perceived shorter and larger than in physical space, respectively. Furthermore, depth perception in the photograph had an anisotropic property. In Experiment 2, the same objects as in Experiment 1 were observed directly by the subjects. The distances and the angles in the direct observation were perceived longer and smaller at longer distance than in the photograph, respectively. It was concluded that depth perception in the photograph did not reproduce depth either in physical space or in visual space, but it was closer to depth in visual space than in physical space. Furthermore, photographic space had an anisotropic property as visual space did.

Adult↗

PubMed1996

Disability and health: perceptions of a sample of elderly people.

The background to this work was the expected increase in the proportion of elderly people in the population, giving rise to a greater demand for services at a time of scarcity of healthcare resources. The aims of the study were to investigate disability and health in a sample of elderly people living at home in the community. We wished to obtain detailed information about physical disability and health then to explore individual perceptions of health and disability and, finally, to examine relationships between the objective assessments and individual, subjective perceptions. The results reported here represent only part of the work of a larger study which also investigated the use of health and social services in this sample of elderly people. In-depth interviews were undertaken with a random stratified population sample of 200 elderly people living at home. Analysis of interview data showed that, by use of a multidimensional scale of disability, just over one-third of the sample could be classified as 'disabled'. The mobility status of the sample was, in general, good with only small numbers spending most of their time in a wheelchair. The total sample scored highly on activities of daily living, though those classified as disabled were significantly less independent. The mean number of reported health conditions was less than might have been expected in an elderly population. One-third of the subjects in the sample showed discrepancies between their own assessment of their disability and objective assessments. These discrepancies could partly be explained by a combination of individuals' assessment of their own abilities and their beliefs about factors influencing disability. Measures of disability, or activity associated with daily living, were related to perceptions of health, whereas the number of current health problems was not. The factors which determined perceptions of health or disability were: walking unaided and general levels of activity. Health was perceived in terms of what one could do rather than the presence of current diseases or conditions. The results suggested that when planning treatment for elderly people, physiotherapists and others should consider individual variability in perceptions of disability and health, as well as objective assessments. The importance of locomotion in the value systems of elderly people emphasises the high profile of physiotherapy in the care of elderly people.

Activities of Daily Living↗

PubMed2000

A Differential Geometric Description of the Relationships among Perceptions.

We present a differential geometric method for measuring and characterizing the perceptions of an observer of a continuum of stimuli. Because the method is not based on a model of perceptual mechanisms, it can potentially be applied to a wide variety of observers and to many types of visual and auditory stimuli. The observer is asked to identify which small transformation of one stimulus is perceived to be equivalent to a small transformation of a second stimulus, differing from the first stimulus by a third small transformation. The observer's identification of a number of such transformations can be used to calculate an affine connection on the stimulus manifold. This quantity describes how the observer encodes an evolving stimulus as a perceived sequence of "reference" transformations. This type of encoding is a multidimensional generalization of Fechner's method and reduces to his psychophysical scale when the stimulus manifold is one dimensional and the reference transformation is chosen to be a just noticeable difference. The intrinsic aspects of the nature of the observer's perceptions can be characterized by the curvature and torsion tensors derived from the connection. The multidimensional analogues of psychophysical scale functions exist if and only if these quantities vanish. Differences between the affine connections of two observers characterize differences between their perceptions of the same evolving stimuli. The affine connections of two observers can also be used to map a stimulus perceived by one observer onto another stimulus, perceived in the same way by the other observer. Unlike multidimensional scaling techniques, this method does not assume that the observer has a sense of distance (a metric) or that he/she can otherwise compare stimulus pairs that are oriented along perceptually different directions in the manifold. The method was used to measure the affine connections of observers of a dot moving on different background graphics; e.g., a blank screen, a grid, or two converging lines similar to those used to create the Ponzo illusion. The results comprise quantitative measurements of the background graphic's influence on each observer's perceptions of straightness, parallelism, and distance. The measurements demonstrate differences between the perceptions of the two observers. Copyright 2000 Academic Press.

Journal Article↗

PubMed2001

Directed Convergence in Stable Percept Acquisition.

We view a perceptual capacity as a nondeductive inference, represented as a function from a set of premises to a set of conclusions. The application of the function to a single premise to produce a single conclusion is called a "percept" or "instantaneous percept." We define a stable percept as a convergent sequence of instantaneous percepts. Assuming that the sets of premises and conclusions are metric spaces, we introduce a strategy for acquiring stable percepts, called directed convergence. We consider probabilistic inferences, where the premise and conclusion sets are spaces of probability measures, and in this context we study Bayesian probabilistic/recursive inference. In this type of Bayesian inference the premises are probability measures, and the prior as well as the posterior is updated nontrivially at each iteration. This type of Bayesian inference is distinguished from classical Bayesian statistical inference where the prior remains fixed, and the posterior evolves by conditioning on successively more punctual premises. We indicate how the directed convergence procedure may be implemented in the context of Bayesian probabilistic/recursive inference. We discuss how the L(infinity) metric can be used to give numerical control of this type of Bayesian directed convergence. Copyright 2001 Academic Press.

Journal Article↗

PubMed1975

[Correlation between sensory action potentials and vibratory perception in uremic polyneuropathy (author's transl)].

1. The sensory action potentials of the tibial nerve at the medial malleolus were studied by averaging in 51 patients with chronic renal failure treated by hemodialysis. Vibratory sense was also tested quantitatively on the dorsum of the foot with a pallesthesiometer. 2. Good correlation was found between sensory tibial nerve potentials and vibration sense in subclinical as well as in clinical uremic polyneuropathy. A biphasic potential correlated with unaffected vibration sense in 18 out of 23 patients, and impaired vibratory sense with a polyphasic response in 20 of 28 patients. Maximal nerve conduction of sensory fibres was faster (mean 37.4 m/sec) in cases with normal vibratory sense, but slower (mean 31.3 m/sec), when vibratory sense was impaired. Furthermore there was a correlation between the threshold of vibratory perception and sensory nerve conduction. 3. Sensory function, tested with conventional methods, was impaired only 5 times in 28 patients with altered vibratory perception. 4. The earlier impairment, especially of the vibratory sense, may be explained by the following neurophysiological mechanisms: a) Because of the polyphasic prolonged response of the sensory potentials, no rhythmical groups of impulses reach the central nervous system, but only a continual stream of small peaks arrives, so that vibration perception does not develop. b) A multiplication of the frequency of discharges caused by alternating firing of different sensory fibres is impossible due to the reduction of the number of axons. c) The prolongation of the relatively refractory period due to demyelinization of the surviving fibres prevents the transmission of frequent impulses. 5. Alterations of the sensory action potentials of the tibial nerve, as well as of vibratory perception tested quantitatively, are earlier signs of uremic polyneuropathy than the prolonged motor nerve conduction velocity. Since not all patients give accurate information when tests of vibratory sense are performed both methods should be applied. Physiological polyphasia of sensory action potentials and diminishing vibration perception in advanced age must be taken into account.

Action Potentials↗

PubMed1983

Locus of control and control perceptions and the relationship between life stress and psychological disorder.

This study tested the effects of life stress and variables hypothesized to moderate these effects using a multivariate hierarchical regression model. College undergraduates served as subjects. The variables of life stress, dispositional locus of control beliefs, perceptions of control over life event outcomes and psychological disorder were measured at two points in time. At both measurement periods, negative life events were significantly related to psychological disorder. This relationship was found even when initial psychological disorder was statistically controlled. Dispositional locus of control beliefs and control perceptions failed to moderate the effects of life events at either measurement period. Control perceptions appeared to be more a function of event characteristics than subjects' dispositional characteristics, given that these perceptions were unrelated to locus of control beliefs and that the outcomes of negative events were consistently viewed as less controllable than those of positive events. The findings support the relationship between life stress and psychological disorder but they call into question the moderating effects of locus of control beliefs and perceptions of control over life event outcomes.

Adaptation, Psychological↗

PubMed1996

Cancer patients psychological adjustment and perception of illness: cultural differences between Belgium and Turkey.

Little is known about cultural differences in psychological adjustment and perception of illness (PI) during medical procedures in general and radiotherapy in particular. This study compares a Turkish (TP) and a French speaking Belgian (BP) population. A group of 296 consecutive patients attending the radiotherapy clinic of Institut Jules Bordet, Brussels, (n = 172) and Oncology Institute, Capa-Istanbul, (n = 124) were interviewed and assessed by a symptom checklist, the SCL-90-R, at the beginning and at the end of the radiotherapy. PI, derived from a semi-structured interview, was assessed at the beginning of radiotherapy by a five-point observer-rating scale derived from the Omega Vulnerability Rating Scale. Differences in SCL-90-R scores, taking into account country, age, gender, level of education and PI as potential explanatory variables, have been tested by a multivariate analysis of variance with a design of repeated measures using the SCL-90-R scores as dependent variables. Mainly a time effect and a country effect have been found. Some interactions between both effects have also been found. Globally, all the SCL-90-R scores decrease between the beginning and the end of the radiotherapy. The effect of country is noticeable for most of the SCL-90-R components, with higher scores in the BP, except for the positive symptom total score where the TP showed higher scores. The interaction between country and time is not significant, the scores of both the BP and TP decreasing over time, except for somatization scores (P < 0.001) where the scores of the BP were stable over time while the scores of the TP decreased considerably, and for paranoid ideation scores (P = 0.001) where the scores of the BP decreased while the scores of the TP increased. Results showed a higher rate of correct perception in the BP compared to the TP (P = 0.0001). A PI effect has been found for somatization (P = 0.02), anxiety (P = 0.01) and Global Severity Index scores (P = 0.05), with higher mean scores for the "correct perception" category. No interaction with time was found. A significant interaction effect between country and PI has been found for anxiety scores with higher scores in the correct perception category in the BP and in the "denial of implications" category in the TP (P < 0.001). Results highlight cultural differences in psychological adjustment and/or in the responses to self-report questionnaires: greater weight was given to items by the BP, more numerous items were scored by the TP, and greater weight was given to the somatization subscale compared to the psychological subscales by the TP. This study suggests that psychosocial distress is expressed differently in Belgium and Turkey, where patients express mostly somatic complaints. Finally PI, a culture-dependent factor, appears to influence psychological adjustment very differently, a correct perception of illness leading to more anxiety in the BP compared to the TP.

Adaptation, Psychological↗

PubMed2001

[Significance of employment and unemployment in middle and advanced adult age for subjective perception of aging and realization of potentials and barriers of a responsible life].

This contribution proceeds on the assumption that occupational activities in middle and upper adulthood do offer opportunities to use and extend competences and therefore to experience self-efficacy, social participation and acceptance, whereas unemployment is associated with a constriction of personal resources which have a negative impact on subjective perceptions of ones's own aging process, potentials and barriers of leading a productive and responsible life. First, employed and unemployed subjects are compared in their scores on three psychometric scales (perceptions of age-related losses, potentials and barriers of leading a productive and responsible life) and four aspects of the "Lebenslage" (Subjective health status, Perceived social integration, Income of the household, Education). In a further step the predictive power of employment and unemployment for subjective perceptions of one's own aging process, potentials and barriers of leading a productive and responsible life when aspects of the "Lebenslage" and sociostructural variables (Age, Sex, Eastern versus western part of Germany, Areas with high versus low unemployment) are also taken into account. Results, obtained in a stratified sample of 641 subjects between 45 and 57 years, show that employed and unemployed subjects differ in subjective perceptions of one's own aging process, potentials and barriers of leading a productive and responsible life as well as in aspects of the "Lebenslage". Employment and unemployment are significant predictors of subjective perceptions of one's own aging process, potentials and barriers of leading a productive and responsible life even when aspects of the "Lebenslage" and sociostructural variables are already taken into account. Results are interpreted as support for the hypothesis that occupational activities are not only instrumental for the realization of human necessities, but that in middle and upper adulthood employment is to be regarded as a human need in itself.

Activities of Daily Living↗

PubMedDate not supplied

Assessment of cyclodisparity-induced slant perception with a synoptophore.

PURPOSE: To evaluate with a synoptophore slant perception induced by binocular cyclodisparities in normal subjects and to argue for the possibility of abnormal slant perception in patients with cyclo-vertical strabismus. METHODS: A vertical line with cyclodisparities that ranged from 0 degrees to +/- 10 degrees was presented to 17 normal subjects (mean +/- SD age, 28.4 +/- 5.6 years; 11 men and 6 women) with a synoptophore, and the perceived slant of the line in the pitch plane was measured by a matching method. Cyclodisparity thresholds for top-away and top-forward slants were also evaluated by the method of limits in a separate experiment. RESULTS: An incyclodisparity induced top-forward, while an excyclodisparity induced top-away, slant perception. The maximum slant angle was 37 degrees on average at a cyclodisparity of 10 degrees , and the mean slant gain (perceived angle/geometrically calculated angle) was 64 +/- 13%. The mean cyclodisparity thresholds for top-away and top-forward slants were -1.1 degrees and 0.6 degrees , respectively. CONCLUSION: The slant perception induced by cyclodisparities was reasonably assessed with the synoptophore. The cyclodisparity thresholds obtained in this experiment were much lower than the cyclodeviation range of the patients, indicating that a considerable number of patients may have abnormal slant perception once they achieve sensory fusion.

Adult↗

PubMedDate not supplied

Health perception and depressive symptoms among older Korean Americans.

Given the increasing recognition of racial/ethnic health disparities, the present study focused on older Korean Americans. Using data from 230 older Korean Americans in Florida (M age = 69.8, SD = 7.05), we assessed (a) how background variables (demographic information and acculturation), health constraints (chronic conditions and functional disability), and psychosocial factors (sense of mastery and filial satisfaction) were associated with health perception and depressive symptoms; and (b) whether health perception mediated the connections between health constraints and depressive symptoms. We observed positive perceptions of health and emotional states among individuals with higher levels of acculturation, fewer chronic conditions, less disability, and a greater sense of mastery. We also found that persons who were more satisfied with their relationships with adult children and who had more positive health perception were less depressed. Additionally, the findings supported a mediation model of health perception in the linkages between physical and mental health. Findings and implications are discussed here in a cultural context.

Acculturation↗

PubMed2006

Parents' perceptions of causes of and solutions for school violence: implications for policy.

This study explores perceptions of causes of and solutions for school violence in a sample of 202 parents interviewed in the wake of nationally publicized school shootings. We also investigate the effects the school shootings had on children, parents' perceptions regarding firearms, and changes in parenting behavior. Parents exhibited strong support for almost all proposed causes and solutions, and we address their desire for immediate and often invasive interventions to prevent future violence. We contrast parents' perceptions with their own parenting behaviors and with literature on effective interventions. Results are discussed within the context of policy implications.Editors' Strategic Implications: Parents' perceptions and behaviors are frequently influenced by history effects. The national attention received by school shootings provided an opportunity for exploration of those perceptions and self-reported behaviors. The authors provide evidence from timely surveys that parents struggle with identifying causal factors that may contribute to school violence and consequently support a myriad of strategies for intervention including very invasive environmental preventive strategies. The findings suggest that social scientists should play a proactive role in translating research-supported preventive strategies to effective replications in the community and make research available in formats that are available and comprehensible by the lay public.

Adolescent↗