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At least 19 recordsLinked to original sources
PubMed1978

The need for process research on psychophysical judgment: comments on "Ratio and subtractive processes in psychophysical judgment" by Veit.

This article is a commentary on Veit's article "Ratio and Subtractive Processes in Psychophysical Judgment." Veit's article makes an important contribution to the area of psychophysical judgment by providing a systematic approach that combines measurement and psychological theory. Using multi-factor designs and a cross-task scale-invariance criterion, Veit shows how to concurrently examine the integration rule, response-transformation function, and psychophysical function for judgment tasks. The need to expand this methodology to further understand the operations and processes underlying psychophysical judgment is stressed in the present article, and an illustration involving feedback mechanisms is provided.

Feedback↗
PubMed1976

Human psychophysical analysis of receptive field-like properties: IV. Further examination and specification of the psychophysical transient-like function.

In this paper we examine several key properties of the moving 'windmill' target used in evaluation of the psychophysical transient-like function. Magnitude of the transient-like function, herein defined as the difference in threshold-determining background field luminance between stationary and moving windmill conditions, was greatest for a rate of approximately 6-8 on-off transitions/second for the moving windmill. Increasing the light/dark ratio of the windmill also augmented the magnitude of the transient-like function. The one-, two- and four-section 'windmill' targets exhibited essentially similar results, indicating that the number and length of borders do not influence this response. In conjunction with previous stationary windmill results (Enoch and Johnson, 1976), these data define the relevant transient-like function properties and provide a basis for comparison with findings in the companion paper (Enoch, Johnson & Fitzgerald, 1976a) which describes the application of these properties to clinical populations for diagnostic purposes.

Psychophysics↗
PubMedDate not supplied

Psychophysical capacity of industrial workers for lifting symmetrical and asymmetrical loads symmetrically and asymmetrically for 8 h work shifts.

This paper presents comprehensive maximum acceptable weight of lift (psychophysical lifting capacity) database for male and female industrial workers for lifting symmetrical and asymmetrical loads symmetrically and asymmetrically for 8 h work shifts. The experimental data collected in previous studies on experienced (industrial) and inexperienced (non-industrial) materials handlers (Mital 1984a, Mital and Fard 1986) and the patterns of responses between the two populations (Mital 1985, 1987) were used to generate this database. Since previous work (Mital 1985, 1987) showed that responses of both experienced and inexperienced materials handlers to task variables are similar and also provided multipliers relating the psychophysical lifting capacities of the two populations, it was possible: (1) to convert psychophysical capacity data for asymmetrical lifting of symmetrical and asymmetrical loads, collected on inexperienced workers to reflect psychophysical lifting capacity of experienced workers for asymmetrical lifting; and (2) to take psychophysical lifting capacity data of experienced industrial workers for symmetrical lifting of symmetrical loads and generate from it their psychophysical lifting capacity for symmetrical and asymmetrical lifting of symmetrical and asymmetrical loads by using the response patterns of inexperienced workers to lifting symmetrical and asymmetrical loads symmetrically and asymmetrically. Both approaches were used and, as expected, provided almost identical values for the psychophysical lifting capacity of industrial workers for symmetrical and asymmetrical lifting of symmetrical and asymmetrical loads. Therefore, the final database tables provided in this paper used combined values generated by the two methods.

Databases, Bibliographic↗
PubMed1979

Detection of tactile stimuli. Thresholds of afferent units related to psychophysical thresholds in the human hand.

1. Psychophysical thresholds were determined at 162 points in the glabrous skin area of the human hand when slowly rising, triangular indentations of controlled amplitudes were delivered with a small probe. The method of constant stimuli was used with either the two alternative forced choice or the yes-no procedure. It was found that the distribution of the psychophysical thresholds varied with the skin region. Thresholds from the volar aspect of the fingers and the peripheral parts of the palm were low and their distribution was unimodal with a median of 11.2 micrometers. In contrast, there was an over-representation of high thresholds when observations from the centre of the palm, the lateral aspects of the fingers and the regions of the creases were pooled, and the distribution was slightly bimodal with a median of 36.0 micrometers. 2. Nerve impulses were recorded from single fibres in the median nerve of human subjects with percutaneously inserted tungsten needle electrodes. The thresholds of 128 mechanosensitive afferent units in the glabrous skin area of the hand were determined when stimuli were delivered to partly the same points as stimulated for the assessment of the psychophysical thresholds. Of the four types of units present in this area the Pacinian corpuscle (PC) and rapidly adapting (RA) units had the lowest thresholds with medians of 9.2 and 13.8 micrometers, followed by the slowly adapting type I and slowly adapting type II units with medians of 56.5 and 33.1 micrometers. There was no indication of a difference between thresholds of units located in different skin areas. 3. In the region of low psychophysical thresholds there was good agreement between the thresholds of the rapidly adapting and Pacinian corpuscle units and the psychophysical thresholds, particularly at the lower ends of the samples. In the skin regions of high thresholds, on the other hand, practically all psychophysical thresholds were higher than the thresholds of the most sensitive afferent units. Moreover, simultaneous recording of nerve impulses during a detection task indicated that subjects did not detect stimuli strong enough to elicit several impulses in afferent units in this region. 4. Circumstantial evidence led to the conclusion that detection was dependent on one impulse in one or a few rapidly adapting units under optimal conditons in the region of low psychophysical thresholds, whereas it seemed unlikely that activity in Pacinian corpuscle units was crucial. 5. The findings are consistent with the interpretation that human subjects are able to detect an input consisting of a single impulse in a single rapidly adapting unit.

Adolescent↗
PubMed1992

The analysis of visual motion: a comparison of neuronal and psychophysical performance.

We compared the ability of psychophysical observers and single cortical neurons to discriminate weak motion signals in a stochastic visual display. All data were obtained from rhesus monkeys trained to perform a direction discrimination task near psychophysical threshold. The conditions for such a comparison were ideal in that both psychophysical and physiological data were obtained in the same animals, on the same sets of trials, and using the same visual display. In addition, the psychophysical task was tailored in each experiment to the physiological properties of the neuron under study; the visual display was matched to each neuron's preference for size, speed, and direction of motion. Under these conditions, the sensitivity of most MT neurons was very similar to the psychophysical sensitivity of the animal observers. In fact, the responses of single neurons typically provided a satisfactory account of both absolute psychophysical threshold and the shape of the psychometric function relating performance to the strength of the motion signal. Thus, psychophysical decisions in our task are likely to be based upon a relatively small number of neural signals. These signals could be carried by a small number of neurons if the responses of the pooled neurons are statistically independent. Alternatively, the signals may be carried by a much larger pool of neurons if their responses are partially intercorrelated.

Animals↗
PubMed1991

[Psychophysical stress among students of secondary schools during the years of education].

A group of students attended in successive classes of secondary schools were examined in the school-years 1984/85--1987/88. The studied material comprised 165 students (116 girls and 42 boys) beginning education in the first classes. In second classes were 161 students, in third--160 students and in four classes--149 students. The psychophysical stress of the students was assessed by a standardized 77 questions grouped so that it was possible to assess the psychophysical strain connected with school-education, work outside school, day timetable, situation in the class and in the family and physical well-being. The sum of the points obtained in the answers provided information about the general psychophysical stress the answers to certain questions described objectively the stressful situations and the personal experiencing of the troublesomeness++ of them. It was found that with longer time spent in school psychophysical situation of girls and boys was deteriorating because the psychophysical stress from classes to classes was increasing. The psychophysical stress of students in compared classes differed for both sexes. It was greater in girls in successive classes. The objective stressful situations and the personal experiencing of this stress increased among girls from year to year. The psychophysical stress connected with objective situation deteriorated in the fourth classes among boys, nevertheless the subjective experiencing of this stress was raised to its highest value. The final examination (diploma from a European gymnasium) determined a great emotional stress of students, especially for boys.

Adolescent↗
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↗
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↗
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↗
PubMed1990

Electrophysiological and psychophysical flicker sensitivity in patients with primary open-angle glaucoma and ocular hypertension.

Temporal sensitivity was assessed in patients with primary open-angle glaucoma (POAG) and ocular hypertension (OHT). Three measures of flicker sensitivity were obtained: psychophysical modulation thresholds, visual-evoked potentials (VEPs), and focal electroretinograms (FERGs). We found elevated psychophysical thresholds at higher temporal frequencies (30-50 Hz) in patients with POAG, relative to thresholds for age-matched controls. The OHT patients had elevated psychophysical thresholds only at 50 Hz. On the other hand, VEP amplitudes in POAG patients were reduced at all temporal frequencies, with the magnitude of the loss increasing with temporal frequency. The OHT patients, however, showed no reductions in VEP amplitude at any temporal frequency. Finally, POAG patients' FERG amplitudes were reduced at 30-50 Hz; whereas FERG amplitudes in the OHT patients were normal at all temporal frequencies. These results indicate that OHT patients can exhibit psychophysical threshold losses at high temporal frequencies which are not observed in the suprathreshold electrophysiological amplitude measures. On the other hand, patients with POAG show both psychophysical and VEP losses across a range of temporal frequencies. In addition, the decreases in FERG amplitudes in POAG patients suggest changes in the functioning of the outer retina in this disease.

Adult↗
PubMed1990

Tactile roughness: neural codes that account for psychophysical magnitude estimates.

Hypothetical neural codes underlying the sensation of tactile roughness were investigated in a combined psychophysical and neurophysiological study. The stimulus set consisted of plastic surfaces embossed with dot arrays of varying dot diameter and center-to-center spacing. Human subjects explored each surface with the pad of the index finger and reported their subjective sense of roughness magnitude. The same surfaces were scanned across the receptive fields of cutaneous mechanoreceptive afferents in monkeys while recording the evoked action potentials. Hypothetical neural codes for roughness magnitude were computed from the neural response patterns and tested for their ability to account for the psychophysical data. The psychophysical results showed that subjective roughness magnitude is an inverted U-shaped function of dot spacing that peaks near 3.0 mm spacing, and that increased dot diameter produces decreased roughness sensations at all dot spacings. Hypothetical neural codes that do not bear a consistent relationship to roughness magnitude across all of these stimulus conditions can be rejected as the code for roughness. Four types of neural codes were considered. They were based on (1) mean firing rate, (2) general variation in firing rate, (3) short-term temporal variation in firing rate, and (4) local spatial variation in firing rate. Mean firing rate failed to explain the psychophysical results: surfaces that evoked the same firing rate often evoked very different roughness judgments. In contrast, neural codes based on firing-rate variation, especially in slowly adapting afferents, account for the psychophysical results.

Action Potentials↗
PubMed1990

Psychophysical measures of central auditory dysfunction in multiple sclerosis: neurophysiological and neuroanatomical correlates.

Central auditory function was assessed in 15 patients with multiple sclerosis (MS) to determine whether the demyelinating lesions resulted in disruption of temporal processing. Auditory evoked potential (AEP) recordings included all three latency regions: Auditory brain stem responses (ABRs), midlatency responses (MLRs), and long-latency responses (LLRs). Two psychophysical tasks thought to involve temporal processing were used: a monaural-processing task (gap-detection) and a binaural-processing task (masking level difference; MLD). Further, AEP abnormalities and psychophysical performance deficits were related to lesion location, based on magnetic resonance imaging (MRI) scans. Reduced MLDs were seen in six MS subjects. Abnormal MLDs were always accompanied by abnormal ABRs and MLRs, and compared to subjects with normal MLDs, the subjects with abnormal MLDs were more likely to have bilateral abnormalities in the AEPs. Further, MLR indices of abnormal binaural interaction appeared to be specifically related to the psychophysical measure of binaural processing. The MRI data of these patients indicated widespread involvement of the auditory pathway. MS subjects with abnormal MRI signals restricted to levels caudal to the lateral lemniscus did not have abnormal MLDs. Gap-detection thresholds were more resistant to the effects of the demyelinating lesions; only two subjects had abnormal gap-detection thresholds. These subjects had extensive AEP abnormalities (bilaterally, in all three latency regions). The gap-detection thresholds were most specifically related to abnormalities of the LLRs. In addition, the subjects with elevated gap-detection thresholds were the only ones with a prolonged interval between the ABRs and MLRs. Thus, efficient neural conduction between the upper brain stem and auditory cortex appears to be crucial for normal monaural temporal processing. The results indicate that demyelinating lesions can cause deficits in temporal processing in the central auditory pathway. However, auditory temporal processing is not a unitary phenomenon since abnormalities at different levels of the auditory system disrupt different types of temporal processing. Finally, abnormal psychophysical performance was not seen in all subjects with AEP and MRI evidence of involvement of the auditory pathway; rather, these psychophysical measures appeared to be sensitive to disruption only in specific portions of the auditory system.

Adolescent↗
PubMed1992

[Psychophysical load of students in the first year of community secondary schools].

The material comprised 179 first-grade pupils (92 girls and 87 boys) of private high-schools in several big cities. The psychophysical load of pupils was evaluated using a standard questionnaire containing 77 questions. These questions were arranged in groups allowing for estimation of psychophysical load related to school lessons, extracurricular activities, daily timetable, pupil's situation in the class and family, and his psychic feeling. The results were treated statistically; moreover, they were compared with the results of earlier studies on 518 first-grade pupils (346 girls and 172 boys) of public high-schools in the same cities. The results lead to the following conclusions: In both private and public high-schools the psychophysical load of girls exceeded that of boys. Likewise, the objectively existing load-causing situations and subjective feelings of the troublesomeness of these situations were a greater nuisance to girls. Psychophysical loads of these girls and boys were somewhat slighter in private than in public high-schools. This decrease in psychophysical load of girls and boys attending private high-schools is associated with smaller loads related to school lessons and to the pupil's situation in the family and class, as well as is due to his better psychic feeling. Loads related to extracurricular activities were similar for girls and boys, irrespective of the kind of high-school. Loads associated with school timetable were in private schools similar for girls and boys, whereas in public schools they were somewhat higher for girls.

Adolescent↗
PubMed1976

Limulus psychophysics: spectral sensitivity of the ventral eye.

The ventral eye of Limulus contains only one type of photoreceptor. Behaviors mediated by the ventral eye provide an unambiguous representation of the function of that single-receptor type. Such behaviors can be compared with the results of acute, single-cell investigations to assay for the contributions of candidate neural codes in the regulation of behavior (cf. Uttal, 1973). Using an unconditioned tail movement as the response, the psychophysical spectral sensitivity function mediated by the ventral eye of Limulus was measured. This psychophysical function peaked at 525 nm and showed evidence of strong absorption by the cuticle in the short-wavelength portion of the spectrum. Under the conditions of the present experiment, the threshold was 4.5 quanta absorbed per receptor per msec at 525 nm. The spectral transmission of the ventral eye cuticle was also measured. After correction for cuticle absorption, the psychophysical spectral sensitivity function was compared with previously reported spectral sensitivity functions obtained either from electrophysiologic (Millecchia, Bradbury, and Mauro, 1966; Nolte and Brown, 1970) or from microspectrophotometric (Murry, 1966) recordings from single, isolated ventral eye photoreceptor cells. All three functions exhibit a sensitivity peak near 525 nm; the corrected psychophysical and microspectrophotometric functions both display a second peak near 425 nm. A second experiment confirmed the reliability and validity of the 425-nm peak. The coding implications of these findings were explored. A preliminary finding is that, in dichromatic or trichromatic visual systems, two-peaked receptor spectral sensitivity functions produce central, opponent response systems that are qualitatively the same as those produced by single-peaked receptors.

Animals↗
PubMed1978

Compatibility between psychophysical and physiological measurements of aural combination tones.

Neural studies of combination-tone (CT) responses in the eighth nerve and antroventral cochlear nucleus of anesthetized cats give evidence of stimuluslike intracochlear CT's with a similar amplitude spectrum as inferred from human psychophysics. An unsolved problem raised in these studies is the gross discrepency between the phase of CT's measured psychophysically and neurally. It is unknown whether incompatibility lies in the cochleas or the criteria for measuring CT's in the different experiments. New psychophysical experiments were developed to clarify this issue. Secondary CT's (SCT) were generated by the interaction between a primary cubic CT (CTT) and a third tone in the stimulus. The SCT measured by cancellation exhibits similar properties to those of a CT generated by the comparable two-tone stimulus. The SCT is eliminated when the CCT is cancelled. These findings support the view that CT's exist in the cochlea as spatially distinct, stimuluslike excitations, and that CT excitations are eliminated by psychophysical cancellation. The SCT phase provides a measure of the CCT phase without requiring direct cancellation of the CCT. Phase measurements by the new indirect and older direct methods imply that the CT phase may be constant with changing sound level of the primary stimulus as found in the neural studies; these measurements also reveal nonlinear phase effects not found in neural studies. The new data suggest that the CT phase discrepancy may be caused by a real difference between the nonlinear mechanisms in the alert humans and anesthetized cats, and provide new constraints for clarifying this issue through further study.

Acoustic Stimulation↗
PubMed1991

Stimulus features affecting psychophysical detection thresholds for electrical stimulation of the cochlea. I: Phase duration and stimulus duration.

The shapes and levels of psychophysical detection threshold versus frequency functions for sinusoidal electrical stimulation of the deafened cochlea vary from subject to subject. These variations have been shown previously to be correlated with nerve-survival patterns. The shapes of these functions are critical in the design and calibration of analog processors for auditory prostheses. This paper examines two stimulus features that may contribute to the shapes of these functions: phase duration and stimulus duration. Psychophysical experiments were performed with unilaterally deafened and implanted macaque monkeys. Effects of phase duration were studied by measuring thresholds for single symmetric biphasic pulses presented at a rate of 1 per trial. Psychophysical detection thresholds for these pulses decreased, in the region of maximum slope, at a rate averaging -6.2 dB per doubling of phase duration, which is steeper than the rate of decrease in thresholds reported for single auditory-nerve fibers. Slope was weakly correlated with threshold level. Thresholds for long-duration sinusoids were consistently lower and the slopes of the threshold versus phase-duration functions were consistently steeper than those for single pulses. Thresholds for sinusoids and pulse trains decreased as a function of stimulus duration for durations up to at least 300 ms. The rate of decrease as a function of stimulus duration depended on the phase duration of the stimulus, and for long phase-duration signals, it depended on frequency. The rate of decrease was correlated with the absolute-detection-threshold level. We conclude that phase duration contributes significantly to, but does not completely account for, the steep slopes of the threshold versus frequency functions for long-duration sinusoids. Temporal integration is greater for longer phase-duration signals, giving rise to steeper slopes of threshold functions for long-duration sinusoids as compared to those for single pulses in the 1- to 5-ms/phase range. Current neural data and models do not account for the steep slopes of psychophysical threshold functions.

Animals↗