Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Psychophysics”

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 37 records · Page 2Linked to original sources
PubMed1999

Perception of the form of stimulus increment as a method in assessment of the psychophysical relationship.

Among numerous procedures for determination of the psychophysical relation, one approach has seldom been applied. Essential in this method is to present a set of stimuli whose intensity increases in fixed time following different forms. The objective stimulus increment, which the subjects perceive as linear growth directly, represents the inverse psychophysical relation. In this paper the method was tested in the fields of click frequency and sound pressure. This procedure was named "Perception of the Form of Stimulus Increment in Time". In comparison to other psychophysical approaches, this one has several advantages. The principal ones are the following: (1) In assessing the psychophysical relation it is not necessary to try to measure the perceptual magnitude; and (2) the psychophysical relation is directly determined by its dynamic pattern. In this paper modifications to the method are reported which facilitate the subject's task and avoid some differences in subjects' individual approaches to the task. The modified procedure leads to results satisfactory independent of the influence of the factors irrelevant to the psychophysical relationship.

Acoustic Stimulation↗
PubMed2005

Understanding the structural determinants of object confusion in memory: an assessment of psychophysical approaches to estimating visual similarity.

Computer-generated shapes varying on visual dimensions such as curvature, tapering, and thickness have been used to investigate identification deficits in the category-specific visual agnosia (CSVA) Patient E.L.M.. However, whether the implemented variations on each of these dimensions were perceived by novice observers as "similar amounts of change" is unknown. To estimate distance in psychophysical shape space, sets of shapes were developed using two different scaling methods--an objective method based on visual search, and a subjective method based on judgments of similarity--and a third approach that did not involve scaling. How well each method estimated psychophysical shape space was assessed by measuring the confusions within memory among the shapes. The results suggested that, although neither of the approaches perfectly reflected psychophysical shape space, subjective scaling was a better estimator of distance in psychophysical shape space than were other approaches. The number of confusions produced on each set of shapes was used to develop a new set of shapes that accurately estimated distance in psychophysical shape space. These results suggest that a combination of approaches is preferable in order to accurately estimate distance in psychophysical shape space.

Form Perception↗
PubMed1999

Future directions of psychophysical studies.

Psychophysics is a very old branch of psychology that is concerned with the relationship between physical stimuli that occur in the "outside world", and the sensations they produce in the body's "inside world". According to modern psychophysical theory, the strength of a sensation is directly related to the intensity of its physical stimulus by means of a power function. The history and development of psychophysics is briefly reviewed, and the application of psychophysics to manual handling tasks and repetitive hand and wrist motion is described. The advantages and disadvantages of psychophysics are discussed. The following 4 directions for future research are suggested: further validation of the data, expansion into other areas of concern (eg, other body parts, jobs, and postures), broadening of the subject base by including symptomatic subjects, and greater inclusion of psychophysical measures (eg, pain, fatigue, and discomfort) in studies of musculoskeletal disorders.

Ergonomics↗
PubMedDate not supplied

[One solution to the problem of basic psychophysical law and sensory scaling].

One of the central problems of psychophysics has been considered, namely, the problem of existence and uniqueness of the fundamental psychophysical law and direct sensory scaling. Based on the stochastical model of stimulus processing it was concluded that the Stevens' law should be regarded as the fundamental psychophysical law. A method for analytical description of direct sensory scales has been suggested. It is shown that two principal branches of psychophysical research--sensory sensitivity and psychophysical scaling--are naturally combined by the proposed stochastical perception model forming a unified psychophysical science.

Models, Theoretical↗
PubMed1984

A comparison of force and depth of skin indentation upon psychophysical functions of tactile intensity.

Tactile sensory intensities related to force applied to the skin, and depth of skin indentation were measured with a magnitude estimation procedure at various sites on the left hand of four human subjects. These same skin sites were measured for "compressibility"--that is, the indentation depths that resulted from controlled forces. Graphic examination of the magnitude estimation data indicated that, in most cases, growth of sensory intensity was relatively shallow at the lower stimulus intensities, and steeper at higher stimulus intensities. The "breakpoint" between the shallow and the steep legs of the psychophysical functions was routinely found between 0.30 and 0.40 mm of indentation, and between 12.0 and 20.0 mN of force. Two subjects consistently produced positively accelerating psychophysical functions, whereas the other two produced negatively accelerating or nearly linear functions above the breakpoint. Differences in skin compressibility did not systematically alter the exponent of the psychophysical functions, regardless of the stimulus dimension (i.e., force or depth of skin indentation). Psychophysical functions based on controlled depth of skin indentation, at a constant rate of indentation, consistently produced higher r2 values than psychophysical functions based on controlled force. When the exponents of psychophysical functions based on controlled skin indentation were compared across different regions of the hand, the values were ordered such that dorsum of hand greater than finger greater than thenar. It was concluded that tactile sensory intensity is more closely related to depth of skin indentation than to force, but only when the rate of skin indentation is controlled.

Female↗
PubMed1994

Neuronal and psychophysical sensitivity to motion signals in extrastriate area MST of the macaque monkey.

We recorded the responses of single neurons in extrastriate area MST while rhesus monkeys discriminated the direction of motion in a set of stochastic visual displays. By varying systematically the strength of a coherent motion signal within the visual display, we were able to measure simultaneously the monkeys' psychophysical thresholds for direction discrimination and the responses of single neurons to the same motion signals. Neuronal thresholds for reliably signaling the direction of motion in the visual display were calculated from the measured responses using a method based in signal detection theory. Neurons in MST were exquisitely sensitive to motion signals in the display, having thresholds for discriminating the direction of coherent motion that were, on average, equal to the psychophysical thresholds of the monkeys. For many MST neurons, the intensity of the response was correlated with the monkey's psychophysical judgements for repeated presentations of a given near-threshold stimulus; the monkey tended to choose the preferred direction of the neuron under study when that neuron responded more strongly to the stimulus. In both of these respects, MST neurons were indistinguishable from neurons in extrastriate area MT, a major source of afferent input to MST. In a second set of experiments, we found that both of these results held true in the face of pronounced manipulations of the visual stimulus. Severe reductions in stimulus size and speed, for example, compromised neuronal and psychophysical sensitivities by similar amounts so that the average neuronal and psychophysical thresholds remained approximately equal. In addition, the trial-to-trial covariation of neuronal response and perceptual decision was unaffected by our stimulus manipulations. Thus, MST neurons carry signals appropriate for supporting psychophysical performance on our task over an impressively wide range of stimulus configurations.

Animals↗
PubMed1981

Physiological (waves I and V) and psychophysical tuning curves in human subjects.

Tuning curves obtained on wave I (VIII nerve) and wave V of the auditory brainstem response were recorded simultaneously with ear-canal and forehead electrodes. On these same human subjects using the same acoustic stimuli psychophysical tuning curves were also measured. For each subject the three tuning curves were qualitatively similar; however, both intra- and inter-subject quantitative differences were present. The best agreement was between the psychological and the wave V tuning curves. The wave I tuning curve differed from the other two mainly on the high-frequency side by showing a wider response area. The main difference between both physiological tuning curves and the psychophysical tuning curve occurred near center frequency of the probe signal: Physiological tuning curves had deeper tips in comparison to the psychophysical tuning curves which had shallow rounded tips. This might be due to energy splatter of the short-duration signal which can significantly effect psychophysical judgments while minimally contributing to the physiological responses. A precise measure of sharpness of tuning was difficult to obtain; however, the response area of wave I appears to be more biased towards high-frequency cochlear neurons than either wave V or psychophysical judgments. Tuning curves are shown to be a viable method of relating physiological to psychophysical measurements in human subjects.

Action Potentials↗
PubMed1991

[Changes in psychophysical load of high school students as a result of educational reform].

The material comprised 2679 secondary school pupils (1959 girls and 1020 boys) from several Polish big cities, among whom 1281 pupils took up the old school program and 1968--the new program. The present studies were initiated in school year 1985/86 and were completed in 1989/1990. The psychophysical load of pupils was evaluated by means of a standard questionnaire comprising 77 questions grouped into problems, allowing us to determine the pupil's psychophysical load associated with school education, extra school occupations, daily time-table, situation in the class and family as well as psychic general feeling. The overall score obtained for all answers informed about the total psychophysical load. Answers to selected questions objectively specified the prevailing load-causing situations, as well as estimated the subjective feeling of the burden of these loads. The results led to the following conclusions: both prior to and after the introduction of changes in school programs (educational reform), the overall psychophysical situation of girls and boys deteriorated with years of school education. Introduction of changes in school programs has led to an increase overall psychophysical load of pupils in all classes compared, with the exception of the final class (before the examination for the secondary-school certificate). After the educational reform, the load was heaviest in the second class of secondary school. The psychophysical load of girls exceeded that of boys. Likewise, the loads associated with the objectively prevailing load-causing situations as well as those associated with subjective feeling of the burden of these loads were heavier in girls than in boys, both before and after the introduction of changes in school programs.

Adolescent↗
PubMed2002

Dependence of vibrotactile thresholds on the psychophysical measurement method.

OBJECTIVES: To investigate the dependence of vibrotactile thresholds on the psychophysical method used in the diagnosis of neurological dysfunction caused by exposure to hand-transmitted vibration. To compare thresholds obtained with (a) 'continuously variable' versus intermittent 'staircase' stimulation using 'yes-no' responses, and (b) 'yes-no' and 'forced-choice' responses using intermittent staircase stimulation. METHODS: Vibrotactile thresholds were measured on 12 healthy men by three different psychophysical methods. All measurements were performed with the same vibrometer in which the vibratory stimulus was applied by a probe 6 mm in diameter that protruded through a hole of 10 mm diameter in a surround, controlling both the contact force and the push force. Four stimulus frequencies (16, 31.5, 63 and 125 Hz) were used to obtain responses from FAI and FAII mechanoreceptors. RESULTS: There was a 3 to 6 dB variation in threshold due to the psychophysical method: thresholds were lower with intermittent stimulation and thresholds obtained with the 'forced-choice' procedure were lower than those obtained with the 'yes-no' procedure. Alternative explanations of the findings were offered. CONCLUSIONS: The dependence of psychophysical measurement method on vibrotactile thresholds was partly due to influencing responses via mechanoreceptor systems. It was suggested that the psychophysical measurement method had a sufficiently large effect on vibrotactile thresholds for it to be taken into account when methods for the diagnosis of neurological disorders are standardised.

Adult↗
PubMed2004

Modeling the relationship between psychophysical perception and electrically evoked compound action potential threshold in young cochlear implant recipients: clinical implications for implant fitting.

OBJECTIVE: In cochlear implant recipients, the threshold of the electrically evoked compound action potential (ECAP) has been shown to correlate with the perceptual detection threshold and maximum comfortable loudness levels (respectively, T- and C-levels) used for implant programming. Our general objective was to model the relationship between ECAP threshold and T/C-levels by taking into account their relative changes within each subject. In particular, we were interested in investigating further the validity of ECAP threshold as a predictor of psychophysical levels, depending on intra-cochlear electrode location and time of testing (from 1 to 18 months post-implantation). METHODS: A total of 370 ECAP thresholds, measured in 49 children, using a Nucleus 24 cochlear implant, were compared with the corresponding T- and C-levels obtained at the same visit, for the same electrode. Response profiles for the whole group of patients were modeled across four test electrodes spaced equally along the electrode array from base towards apex. A linear regression model was constructed and the quality of the ECAP threshold-based predictions was assessed by testing for correlation between measured and predicted psychophysics. Comparison was made with a more simplistic model (described here as the 'parallel profiles method') stipulating, within each subject, a 1 microA increase in psychophysical levels for every 1 microA increase in ECAP threshold. RESULTS: Offset between ECAP threshold and psychophysics profiles was found to vary significantly along the electrode array for the T-, but not for the C-level. In contrast with the parallel profiles method, our regression model predicted, within each subject, an average increase of 0.23 microA (95% confidence interval: 0.18-0.28) in T-level for every 1 microA increase in ECAP threshold. This correction improved the quality of T-level prediction when our model was run using measured T-level and ECAP threshold from a reference electrode (r=0.77 vs. r=0.62). The shorter the distance between the electrode for which T-level was predicted and the one used as reference, the stronger the correlation between measured and predicted T-levels. In addition, poorer T-level predictions were obtained at the basal end of the array during the first 3 months post-implantation. In contrast to T-level, individual changes in C-level with ECAP threshold exhibited heterogeneous patterns across subjects so that no common coefficient could account for these changes. However, applying the parallel profiles method led to high-quality C-level prediction. CONCLUSIONS AND SIGNIFICANCE: The results suggest that covariation between ECAP thresholds and psychophysics plays a decisive role in the relationship of ECAP threshold with T-, but not with C-level. Therefore, our regression model and the parallel profiles method should both be used for predicting, respectively, the T- and the C-levels. Although the predictability of our regression model seems to be better for middle and apical electrodes, its utilization should be extended to basal electrodes after 6 months' implant use.

Action Potentials↗
PubMed2000

Psychophysical assessment of assistive devices for transferring patients/residents.

This article reports the psychophysical assessment of nine battery-powered lifts, a sliding board, a walking belt, and a baseline manual method for transferring nursing home patients/residents from a bed to a chair. A separate article reports the biomechanical evaluation of the same task and devices. The objectives of the psychophysical assessment were to investigate the effects of resident-transferring methods on the psychophysical stress to nursing assistants performing the transferring task, and to identify transfer methods that could reduce the psychophysical stress reported by nursing assistants. Nine nursing assistants served as test subjects. Two elderly persons participated as residents. The results indicated that the psychophysical stresses on nursing assistants were significantly lower when performing resident transfers with some of the assistive devices than when performing transfers with the baseline manual transfer method. The nursing assistants generally preferred the basket-sling lift and stand-up lift to other methods. The residents' comfort and security ratings indicated the comfort and security with most of the assistive devices were greater than or equal to the baseline manual method. Most of the comments of the nursing assistants and residents on the assistive devices were favourable.

Humans↗
PubMedDate not supplied

A laterally interconnected neural architecture in MST accounts for psychophysical discrimination of complex motion patterns.

The complex patterns of visual motion formed across the retina during self-motion, often referred to as optic flow, provide a rich source of information describing our dynamic relationship within the environment. Psychophysical studies indicate the existence of specialized detectors for component motion patterns (radial, circular, planar) that are consistent with the visual motion properties of cells in the medial superior temporal area (MST) of nonhuman primates. Here we use computational modeling and psychophysics to investigate the structural and functional role of these specialized detectors in performing a graded motion pattern (GMP) discrimination task. In the psychophysical task perceptual discrimination varied significantly with the type of motion pattern presented, suggesting perceptual correlates to the preferred motion bias reported in MST. Simulated perceptual discrimination in a population of independent MST-like neural responses showed inconsistent psychophysical performance that varied as a function of the visual motion properties within the population code. Robust psychophysical performance was achieved by fully interconnecting neural populations such that they inhibited nonpreferred units. Taken together, these results suggest that robust processing of the complex motion patterns associated with self-motion and optic flow may be mediated by an inhibitory structure of neural interactions in MST.

Animals↗
PubMed2001

Estimation of psychophysical levels using the electrically evoked compound action potential measured with the neural response telemetry capabilities of Cochlear Corporation's CI24M device.

OBJECTIVE: The goal of this study was to estimate psychophysical levels using the electrically evoked compound action potential (EAP), measured with the Neural Response Telemetry capabilities of Cochlear Corporation's Nucleus CI24M cochlear implant system. DESIGN: Twelve postlingually deafened adults with at least 3 mo of implant experience with the CI24M were subjects in this study. EAP growth functions were successfully quantified on each active electrode of every subject. Correlation and regression analyses were performed between EAP measures and cochlear implant fitting psychophysics. Other information including performance, etiology and duration of hearing loss, and individual electrode impedance was considered. RESULTS: EAP thresholds were found to be highly correlated with psychophysical thresholds. The rate of EAP growth with increasing stimulation levels was also found to be correlated with the dynamic range of loudness limits and psychophysical thresholds in some subjects. No relationship was evident between EAP measures and speech perception tests. CONCLUSIONS: Information from EAP growth function measurements may be used to estimate psychophysical information used in cochlear implant fitting but not to predict performance with the device.

Adult↗
PubMed2002

Correlation between optical and psychophysical parameters as a function of defocus.

PURPOSE: To evaluate how ocular optical image quality and psychophysical estimates of visual performance compare to each other as a function of defocus. METHODS: We measured the optical modulation transfer function using a double-pass apparatus and psychophysical estimates of visual performance: contrast sensitivity function (CSF) and visual acuity. Both sets of data were obtained under the same optical conditions. RESULTS: We measured optical and psychophysical parameters as a function of defocus. We studied the correlation between optical parameters (Strehl ratio and the logarithm of the volume in the double-pass image [log_Vol D-P]) and psychophysical parameters (the area under the fitted CSF represented in a logarithmic scale with the spatial frequency in linear scale [Area CSF-log_lin] and visual acuity) for different values of defocus. CONCLUSIONS: Strehl ratio is well correlated with the psychophysical estimates of the visual performance for moderate amount of defocus (within 1 D), whereas the other parameter (log_Vol D-P) is well correlated for larger ranges of defocus (within 2 D) and for different pupil diameters. These results suggest that optical measurements could be used for clinical testing of ophthalmic optics.

Adult↗
PubMed2005

Investigation of psychophysical measure for evaluation of similar images for mammographic masses: preliminary results.

We investigated a psychophysical similarity measure for selection of images similar to those of unknown masses on mammograms, which may assist radiologists in the distinction between benign and malignant masses. Sixty pairs of masses were selected from 1445 mass images prepared for this study, which were obtained from the Digital Database for Screening Mammography by the University of South Florida. Five radiologists provided subjective similarity ratings for these 60 pairs of masses based on the overall impression for diagnosis. Radiologists' subjective ratings were marked on a continuous rating scale and quantified between 0 and 1, which correspond to pairs not similar at all and pairs almost identical, respectively. By use of the subjective ratings as "gold standard," similarity measures based on the Euclidean distance between pairs in feature space and the psychophysical measure were determined. For determination of the psychophysical similarity measure, an artificial neural network (ANN) was employed to learn the relationship between radiologists' average subjective similarity ratings and computer-extracted image features. To evaluate the usefulness of the similarity measures, the agreement with the radiologists' subjective similarity ratings was assessed in terms of correlation coefficients between the average subjective ratings and the similarity measures. A commonly used similarity measure based on the Euclidean distance was moderately correlated (r=0.644) with the radiologists' average subjective ratings, whereas the psychophysical measure by use of the ANN was highly correlated (r=0.798). The preliminary result indicates that a psychophysical similarity measure would be useful in the selection of images similar to those of unknown masses on mammograms.

Algorithms↗
PubMed1976

Primate flicker sensitivity: psychophysics and electrophysiology.

A quantitative comparison is made between the psychophysical flicker response of man and similar data obtained electrophysiologically from the cones of macaque monkeys. When the psychophysical data are obtained from an eye that is strongly light-adapted, there is excellent agreement between the two sets of data at high frequencies. Under this condition, both kinds of data fit a distributed-parameter model, whose time constant also agrees with that derived from studies of the phosphenes elicited by electrical stimulation of the human eye. On the other hand, psychophysical data obtained with fully modulated stimuli (which minimally adapt the eye) yield a longer time constant for the same model. These results imply that the psychophysical flicker thresholds are normally controlled by a distributed filtering process that is proximal to the receptor stage. This slower, psychophysical process is evidently desensitized by intense adapting lights, so that the faster one that governs the electrophysiological responses can be detected.

Animals↗
PubMed1997

End stopping and length tuning in psychophysical spatial filters.

Psychophysical spatial filters or channels are usually modeled after simple-cell receptive fields, although many cortical cells are end stopped and length tuned. Using psychophysical masking, we demonstrate an analog to receptive field end stopping and length tuning in psychophysical spatial filters tuned to a wide range of spatial frequencies. Specifically, masking is maximal when the mask is approximately 5-6 arcmin longer than the target but is reduced when the mask exceeds this length, consistent with the properties of end-stopped cells. The strength and the extent of psychophysical end stopping appear to be determined by filter's spatial-frequency tuning, but length tuning varies with target length. The latter implies that spatial filters tuned to the same spatial frequency could have different length tuning and that there is no fixed length-to-width ratio of the filter size. Phase effects suggest linear length summation but nonlinear psychophysical end stopping which suggest that both first- and second-order visual processing is involved in end-stopped spatial filters.

Adult↗
PubMed1983

Orientational anisotropy in the human visual system: an evoked potential and psychophysical study.

Orientational anisotropy in the human visual system was investigated using electrophysiological and psychophysical techniques. Grating patterns of various orientations were presented and contrast detection thresholds were measured using a two alternative forced choice procedure. Using the same observers, visual evoked cortical potentials (VECPs) were elicited by identical gratings set at various contrasts ranging from subthreshold to high levels. Plots of contrast sensitivity versus grating orientation were derived using the amplitude of a negative wave of the VECP for low contrast data and the amplitude of a positive wave for moderate to high contrast data. These plots were compared with plots obtained during the psychophysical experiment. The results indicate that the low contrast VECP functions exhibit an orientational anisotropy that is qualitatively and quantitatively similar to that observed in the psychophysical data. The high contrast VECP functions, however, exhibit an orientational effect that is qualitatively similar but greater in magnitude than that found in the low contrast VECP or psychophysical experiments. These findings suggest that the amplitudes of VECPs elicited by low contrast stimuli are highly correlated with psychophysical detection performance, and that an additional physiological mechanism is reflected in the VECPs elicited by moderate to high contrast stimuli.

Cerebral Cortex↗