SEARCH · PubMed Health

Results for “Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 793 records · Page 44Linked to original sources

PubMed2004

Perception, action, and Roelofs effect: a mere illusion of dissociation.

A prominent and influential hypothesis of vision suggests the existence of two separate visual systems within the brain, one creating our perception of the world and another guiding our actions within it. The induced Roelofs effect has been described as providing strong evidence for this perception/action dissociation: When a small visual target is surrounded by a large frame positioned so that the frame's center is offset from the observer's midline, the perceived location of the target is shifted in the direction opposite the frame's offset. In spite of this perceptual mislocalization, however, the observer can accurately guide movements to the target location. Thus, perception is prone to the illusion while actions seem immune. Here we demonstrate that the Roelofs illusion is caused by a frame-induced transient distortion of the observer's apparent midline. We further demonstrate that actions guided to targets within this same distorted egocentric reference frame are fully expected to be accurate, since the errors of target localization will exactly cancel the errors of motor guidance. These findings provide a mechanistic explanation for the various perceptual and motor effects of the induced Roelofs illusion without requiring the existence of separate neural systems for perception and action. Given this, the behavioral dissociation that accompanies the Roelofs effect cannot be considered evidence of a dissociation of perception and action. This indicates a general need to re-evaluate the broad class of evidence purported to support this hypothesized dissociation.

Behavior↗

PubMed2004

Which mechanical invariants are associated with the perception of length and heaviness of a nonvisible handheld rod? Testing the inertia tensor hypothesis.

It has been suggested that the inertia tensor governs many instances of haptic perception. However, the evidence is inconclusive because other candidate mechanical parameters (i.e., invariants) were not or were insufficiently controlled for in pertinent experiments. By independently varying all candidate mechanical parameters, the authors were able to test the role of the inertia tensor relative to that of other mechanical parameters. The results showed that length perception during rod wielding is not governed by the inertia tensor alone but also by the static moment. In contrast to previous reports, length perception during rod holding and heaviness perception during rod wielding were found to be unrelated to the inertia tensor and strongly related to the static moment.

Adult↗

PubMed2003

Auditory influences on visual temporal rate perception.

Visual stimuli are known to influence the perception of auditory stimuli in spatial tasks, giving rise to the ventriloquism effect. These influences can persist in the absence of visual input following a period of exposure to spatially disparate auditory and visual stimuli, a phenomenon termed the ventriloquism aftereffect. It has been speculated that the visual dominance over audition in spatial tasks is due to the superior spatial acuity of vision compared with audition. If that is the case, then the auditory system should dominate visual perception in a manner analogous to the ventriloquism effect and aftereffect if one uses a task in which the auditory system has superior acuity. To test this prediction, the interactions of visual and auditory stimuli were measured in a temporally based task in normal human subjects. The results show that the auditory system has a pronounced influence on visual temporal rate perception. This influence was independent of the spatial location, spectral bandwidth, and intensity of the auditory stimulus. The influence was, however, strongly dependent on the disparity in temporal rate between the two stimulus modalities. Further, aftereffects were observed following approximately 20 min of exposure to temporally disparate auditory and visual stimuli. These results show that the auditory system can strongly influence visual perception and are consistent with the idea that bimodal sensory conflicts are dominated by the sensory system with the greater acuity for the stimulus parameter being discriminated.

Acoustic Stimulation↗

PubMed1985

Perception of orientation of motion as affected by change in divergence of texture, change in size, and in velocity.

When there is relative motion between an observer and a textured surface such as the ground, motion-related visual information is available about the orientation of the surface through vergence of the paths of the elements of the texture, change in their sizes and in their velocities. This experiment determined the perceptual effectiveness of each variable in foveal and peripheral viewing for producing perceptions of three-dimensional motion. The three variables were electronically separated and displayed singly, in all possible pairs, and all together. Subjects communicated their perceptions of degree of perceived surface tilt at the top, bottom, and middle of the display for the eight different combinations of variables because, during pilot work perceived surface bendings were frequently noted where top, bottom, and middle appeared tilted to different extents. All three variables can lead to relatively reliable perceptions of perceived orientation of the plane of motion, with change in velocity being the most powerful determiner. Change in size was the weakest. Certain combinations can lead to perceptions of extreme warping and should be avoided in motion displays. Subjects consistently underestimate the amount of simulated tilt. Foveal viewing was more accurate than peripheral viewing but peripheral performance was adequately consistent as an input channel for some orientation tasks.

Depth Perception↗

PubMed1977

The development of knowledge about visual perception.

This chapter describes recent theory and research in one limited area of social-cognitive development, namely, the childhood acquisition of knowledge about visual perception. The author and his co-workers have hypothesized that there are two developmental levels of such knowledge. At earlier-developing Level 1, the child understands that others as well as the self see objects, and is also able to infer correctly what objects they do or do not currently see if provided with adequate cues. At later-developing Level 2, the child understands not only that people can see objects, but also that they can have differing visual experiences while seeing the same object; most notably, they can have different spatial perspectival views of it when looking at it from different positions. Arguments and evidence for the developmental distinction between Level 1 and Level 2 knowledge are briefly presented in Section I. A more detailed model of Level 1 knowledge is presented in Section II, together with an account of several studies of its development during the first four years of life. During these early years, children appear to learn a great deal about how to produce visual percepts in others (showing and pointing to things), how to deprive others of percepts (hide objects), and how to diagnose the percepts they currently have (follow others' direction of gaze and pointing gestures). Section III similarly reviews recent theory and research on the development of Level 2 perspective-taking knowledge in older children. This work is focused mainly on the acquisition and use of very general perspective-taking rules, such as the rule that two observers who look at an object array from the same spatial position must on that account necessarily have identical perspectival views of the array. Section IV described further developmental research that could be or is being done on Level 2 knowledge, Level 1 knowledge, and on the Level 1-Level 2 distinction.

Age Factors↗

PubMed1997

Speech perception skills and speech production intelligibility in French children with prelingual deafness and cochlear implants.

OBJECTIVE: To examine speech perception and production intelligibility in French children with prelingual deafness who received multichannel cochlear implants. DESIGN: Within-subject, repeated-measures design for assessing speech perception and a cross-sectional design for assessing overall speech intelligibility. SETTING: A pediatric cochlear implant center. SUBJECTS: Sixty-four French children with prelingual deafness who received multichannel cochlear implants (mean age at time of implantation, 3 years 11 months) underwent assessment for speech perception. A subset of 16 children who received implants by 3 years of age underwent assessment for speech intelligibility. MAIN OUTCOME MEASURES: Speech perception skills were assessed using phoneme detection, closed-set word and sentence recognition, and modified open-set (MOS) recognition. Speech intelligibility was assessed by asking 50 listeners to identify recorded speech samples from the subjects. Dependent variables for the studies consisted of percent of correct items. RESULTS: After implantation, all children were able to detect phonemes by 3 months. Closed-set word and sentence identification reached 100% accuracy by 48 months (7 children with 4 years of implantation experience). Some children (8 of 48) demonstrated some MOS recognition after 1 year. Modified open-set recognition averaged 67.9% by 42 months (12 children available) and 80% by 48 months (7 children available). Overall speech intelligibility was 4.2% after 1 year, 30.7% after 2 years, 55.2% after 3 years, and 74.2% after 4 years. Within-subject comparison of MOS recognition and overall speech intelligibility scores revealed an insignificant trend for high perceptual performance to be associated with higher speech intelligibility scores (P = .17). There also was a tendency for higher performance to be associated with longer implantation experience. CONCLUSIONS: Speech perception scores appear to increase with increased experience using a cochlear implant. Overall speech intelligibility appears to steadily improve with increased experience and appears to be poorly related to perceptual performance on MOS recognition tasks.

Child, Preschool↗

PubMed1981

The family meets the hospital. Predicting the family's perception of the treatment program from its problem solving style.

A family's perception of a treatment program may determine whether ir becomes productively engaged or destructively withdrawn. A theory of family types, in conjunction with a standardized laboratory problem solving procedure, was used to predict the nature of families' shared perceptions of a psychiatric ward. The individual and shared perceptions of thirty families were determined by means of a specially designed Q-sort. Two dimensions of problem solving behavior successfully predicted significant differences between families in their shared perceptions. Configuration, or the family's capacity to derive effective solutions in the laboratory, predicted the subtlety to their perception of the ward. Coordination, or the capacity of family members to dovetail their problem solving effort with one another, predicted the family's sense of comfort and engagement in the ward setting.

Adolescent↗

PubMed2004

Coping after cancer: risk perceptions, worry, and health behaviors among colorectal cancer survivors.

This study asks whether the experience of cancer motivates healthy behavior change. Further, we asked whether such changes relate to risk perceptions and worry, as suggested by Leventhal's Parallel Processing Model. Male (n=41) and female (n=40) survivors of colorectal cancer were interviewed 1-14 years after they first completed treatment. Younger age was associated with stronger risk perceptions, more worry, and greater anxiety. Shorter-term, compared to longer-term survivors, reported higher risk perceptions and more frequent intrusive thoughts. Greater perceived risk, worry and anxiety correlated positively with intentions to make positive health behavior changes. Overall, these survivors did not report exaggerated risk perceptions, and they were not overly worried or anxious about cancer recurrence. However, low-level risk perceptions, worry, and anxiety motivated interest in adopting protective health behaviors.

Adaptation, Psychological↗

PubMed2001

Speech perception, lexicality, and reading skill.

This study examined the interaction between speech perception and lexical information among a group of 7-year-old children, of which 26 were poor readers and 36 were good readers. The children's performance was examined on tasks assessing reading skill, phonological awareness, pseudoword repetition, and phoneme identification. Although good readers showed clearly defined categorical perception in the phoneme identification task for both the /bif/-/pif/ and the /bis/-/pis/ continua, the category boundary for /bif/-/pif/ was at longer VOTs than the boundary for /bis/-/pis/, which characterizes the classic lexicality effect. Poor readers showed less sharply defined categorical perception on both continua. Although poor readers did not show the classic lexicality effect, lexicality did affect the overall rate with which phonemes were identified as /b/ or /p/ at each VOT. These findings suggest that the lexicon may operate as a compensatory mechanism for resolving ambiguities in speech perception. Furthermore, statistical correction for group differences in phoneme identification made group differences in phoneme deletion disappear, suggesting that deficits in speech perception may play a causal role in the phonological core deficit associated with reading failure.

Awareness↗

PubMedDate not supplied

Perceptions of body size and obesity: a selected review of the literature.

In this article, the literature on body image and related obesity perceptions is discussed. Research findings which span a 20 year period are summarized. Initially, Cheryl Rittenbaugh's concept of obesity as 'a culture bound syndrome' serves as a rationale for understanding sociocultural dimensions of body size perceptions. In this regard, the premise that perceptions of obesity and overweight have cultural determinants is substantiated in the reviewed literature. Societal preferences for body build and size and attitudes about weight are examined as a framework for understanding the impact that social perceptions have on individuals who are either overweight or obese. As a result of negative attitudes toward fatness, stigmatization of overweight people has been consistently documented. In related studies, investigators have centered on self-perceptions of obese and overweight individuals. According to the data, the existence of body image disturbance among extremely overweight individuals is a common phenomenon. However, evidence is also presented that suggests that normal weight individuals (especially women) may also have difficulty in accurately assessing their body size. The final focus of this paper is the relationship between body image and weight change behavior. As indicated in the discussion, this area of research has received the least amount of attention in the literature, and the present findings are contradictory. The paper concludes with recommendations for future research directions.

Body Image↗

PubMed1995

Regional variation in service system performance: comparing the perceptions of key stakeholders.

Area variation studies rarely focus on perceptions of service system performance in their comparative analyses. Using an instrument designed specifically for assessing key stakeholders' perceptions of the performance of mental health service delivery systems, this study compared three areas in Massachusetts that differ significantly with regard to service system structure and resource allocation. Despite these differences, key stakeholders' perceptions of service adequacy, availability, quality, and coordination did not vary substantially, although the findings suggest that to some extent organizational structure may have more effect than resource availability and allocation on perceptions of key stakeholders within the three systems. These differences were also of far less magnitude than differences in hospitalization rates and other more traditional measures of service system performance. The authors argue that stakeholders' perceptions should be considered, along with other standard performance measures, in evaluating service system performance.

Efficiency, Organizational↗

PubMedDate not supplied

Patient perception of involvement in medical care: relationship to illness attitudes and outcomes.

OBJECTIVE: The purpose of this study was to explore the relationships among patients' perceptions about the roles they played during medical visits, their subsequent attitudes about their illnesses and treatments, and their self-rated improvement. DESIGN: Questionnaires were completed by patients before, one day after, and one week after their medical visits, and by their physicians following the visits. SETTING: The study was conducted in a general internal medicine faculty practice that provided adult primary care to a largely HMO population. PARTICIPANTS: Adult patients with new or increased symptoms who were capable of reading and understanding the study questionnaire. MAIN RESULTS: Fifty-five patients (47%) reported playing an active role; 62 patients (53%) reported playing a passive role. After adjusting for age, sex, baseline illness ratings, and physician-rated prognosis, "active" patients reported less discomfort (p = 0.04), greater alleviation of symptoms (p = 0.008), and more improvement in their general medical condition (p = 0.04) one week after the visits than did "passive" patients. These differences were not influenced by the roles patients desired to play. Active patients also reported less concern with their illnesses (p = 0.04), a greater sense of control of their illnesses (p = 0.04), and more satisfaction with their physicians (p = 0.02) one day after the visit. Post-visit dysfunction ratings were not related to patients' role perceptions. CONCLUSIONS: Patients' perceptions about their involvement in care appeared to be related to their attitudes about their illnesses as well as to recovery. Further research is needed, however, to determine the factors that influence these role perceptions and to define the types of patients, illnesses, and settings in which the benefits of active-role perceptions are most likely to be realized.

Adult↗

PubMed2000

Haptic interaction with virtual objects. Spatial perception and motor control.

This paper considers interaction of the human arm with "virtual" objects simulated mechanically by a planar robot. Haptic perception of spatial properties of objects is distorted. It is reasonable to expect that it may be distorted in a geometrically consistent way. Three experiments were performed to quantify perceptual distortion of length, angle and orientation. We found that spatial perception is geometrically inconsistent across these perceptual tasks. Given that spatial perception is distorted, it is plausible that motor behavior may be distorted in a way consistent with perceptual distortion. In a fourth experiment, subjects were asked to draw circles. The results were geometrically inconsistent with those of the length perception experiment. Interestingly, although the results were inconsistent (statistically different), this difference was not strong (the relative distortion between the observed distributions was small). Some computational implications of this research for haptic perception and motor planning are discussed.

Distance Perception↗

PubMed2004

Perceptions of environmental opportunities for physical activity in the European Union.

OBJECTIVES: This article is the last in a series of four that present data about physical activity in 15 member states of the European Union collected by the Eurobarometer 58.2. The focus of this article is on the perception of environmental opportunities for physical activity across the European Union. METHODS: Data were collected in 2002 as part of the Eurobarometer by face-to-face interviews. A total of 16,230 respondents age 15 years and older were interviewed. Sample sizes ranged about 1,000 respondents in most nations. Physical activity was assessed with the last 7-days short version of the International Physical Activity Questionnaire (IPAQ). RESULTS: Results indicate relationships between the perceptions of environmental opportunities; gross household income and physical activity level (in MET-hours/per week) of respondents. Respondents who reported lower income and less physical activity had also more negative perceptions of environmental opportunities. Across nations, respondents in Denmark, the Netherlands, Luxembourg, and Western Germany had the highest satisfaction with environmental opportunities for physical activity. In some nations, positive correlations between the perception of environmental opportunities and physical activity levels could be observed. CONCLUSION: Results show variations in the perception of environmental opportunities across the EU. Overall, the majority of respondents rated their environmental opportunities for physical activity favourable.

Adolescent↗

PubMed2000

Changes of the neurotransmitter serotonin but not of hormones during short time music perception.

We studied the impact of the perception of pleasant and unpleasant music, as rated by healthy subjects with a psychometric scale, on the hormones prolactin and ACTH. In addition, the neurotransmitter serotonin (5-HT) was studied using the platelet model for central neurotransmission of 5-HT. We did not observe any significant changes of prolactin and ACTH during the perception of different kinds of music. The 5-HT content of platelets, however, was higher during the perception of pleasant music as compared to the perception of unpleasant music indicating an increased release of 5-HT during unpleasant music (748 ng/10(9) platelets vs. 699 ng/10(9) platelets; p<0.014). The difference of the 5-HT level was significantly correlated to the score of unpleasantness as rated by the subjects. Our data suggest that perception of unpleasant music induces increased release and decreased peripheral and possibly also central intracellular content of 5-HT.

Adrenocorticotropic Hormone↗

PubMed1998

Age-related deterioration of motion perception and detection.

PURPOSE: The purpose of this study was to evaluate the effect of aging on motion detection and perception. METHODS: Forty-six subjects, ages 19-92 years, were asked to view a motion stimulus. Infrared oculography was used to objectively evaluate motion detection by documenting the presence of optokinetic nystagmus as the subjects viewed the stimulus. Subjective responses to motion perception were recorded using a computer joystick. RESULTS: Optokinetic nystagmus was clearly detectable in all 46 subjects. Motion detection and perception thresholds showed age-related deterioration. No relationship was found to gender or age-gender interaction. CONCLUSION: The results indicate motion detection and perception thresholds deteriorate with age. This may reflect a susceptibility to age-related degeneration in specific cortical areas responsible for motion perception as well as neurodegeneration in the retinogeniculate pathway.

Adult↗

PubMed2003

A chamber-experiment investigation of the interaction between perceptions of noise and odor in humans.

OBJECTIVES: This study was designed to investigate human comfort and health effects following exposure to noise and odor and to explore the interaction between perceptions of noise and odor in humans. MATERIALS AND METHODS: Nine healthy subjects were randomly exposed to noise, odor, and their combination, in a 3 x 3 Latin square design for 80 min in an exposure chamber. Continuous noise was broadcast at an average level of 75 dBA by a loudspeaker, and odor was provided by furfurylmercaptan (a coffee-aroma constituent). A standardized 28-item questionnaire, together with mood-scale ratings, nasal dimensions by acoustic rhinometry, addition tests for distraction, and skin humidity, were performed before and at the end of exposure. RESULTS: In the questionnaire investigation, the perceived "sound level" was significantly affected by noise and the combined exposures, while "odor intensity", "air quality", and "need more ventilation" was significantly affected by odor and the combined exposures. Perceptions of symptoms became worse with increasing exposure time, such as perceived "dry nose" and "sleepiness" by odor and combined exposures, "headache" by noise, "concentration difficulty", "general well being", and "stressed by being in the chamber" by noise, odor and combined exposures. In addition, the occurrence of interactions was analyzed by comparison of the ratings of perceived "sound level", "odor intensity", "air quality", and "need more ventilation" during the combined exposure with two single exposures. Insignificant interaction was found but it indicated a decreased tendency to perceptions of discomfort from "odor intensity", "air quality", and "need for more ventilation" when noise was added to odor exposure. CONCLUSION: It may be concluded that noise and odor cause discomfort in humans. Moreover, the study might indicate that additions of noise reduce (mask) the perception of discomfort from odor, and additions of odor have no or little affect on the perception of noise.

Adult↗

PubMed2004

Self-reported adherence to cholesterol-lowering medication in patients with familial hypercholesterolaemia: the role of illness perceptions.

BACKGROUND: The objectives of this study are to describe levels of adherence to cholesterol-lowering medication and to identify predictors of adherence in patients with familial hypercholesterolaemia (FH). DESIGN: Descriptive questionnaire study. METHODS: 336 adults patients with FH attending one of five outpatient lipid clinics in South East England underwent a clinical assessment by a nurse and completed a questionnaire. The questionnaire assessed self-reported adherence to cholesterol-lowering medication, anxiety, depression, and patient perceptions of heart disease. RESULTS: Overall, participants reported high levels of medication adherence, although 63% reported some level of non-adherence. Total medication adherence (never deviating from the regimen) was more likely to be reported by older participants, those with no formal educational qualifications, those with a personal history of cardiovascular disease, those with a lower total cholesterol level, and those with a greater difference between untreated cholesterol levels and current cholesterol levels. The illness perceptions associated with reported total adherence were lower perceived risk of raised cholesterol, perceiving greater control over FH, and perceiving genes and cholesterol to be important determinants of a heart attack. Emotional state was not associated with medication adherence. In logistic regression analysis, predictors of total medication adherence were having personal history of cardiovascular disease, having no formal qualifications, and perceiving genes to be important determinants of a heart attack. CONCLUSIONS: Both clinical factors and patients' illness perceptions were associated with self-reported cholesterol-lowering medication adherence. The association with illness perceptions was small and many of these associations may be a consequence, rather than a cause, of greater adherence. Given this, intervention strategies aimed at helping patients' to establish routines for medication taking may be more effective in increasing adherence than interventions designed to alter perceptions related to taking statins.

Anticholesteremic Agents↗