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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↗
PubMed1995

Conventions of measurement in psychophysics: von Kries on the so-called psychophysical law.

A translation of von Krie's (1882) paper "On the measurement of intensive magnitudes and on the so-called psychophysical law" is accompanied by a commentary. Von Kries claims that intensive magnitudes are not measurable in themselves, because the establishment of an equivalence between different steps in a scale of intensity does not make any sense without further clarification. Where intensive magnitudes are determined in a domain of the natural sciences, he claims this is only a matter of counting, and of the measurement of temporal and spatial magnitudes. Every measurement of intensity should then be reduced to these operations by explicit conventions. Likewise, we can only speak of the measurement of sensations once we have established an arbitrary convention that determines what we will consider equal. The debate whether sensation varies with the logarithm of stimulus intensity or in direct proportion to stimulus intensity, is then not a difference over matters of fact. Instead it is an empty dispute over words that is rooted in misunderstanding.

Humans↗
PubMed2001

Cochlear implant thresholds: comparison of middle latency responses with psychophysical and cortical-spike-activity thresholds.

The electrically evoked middle latency response (EMLR) is a potentially useful measure of activation of the auditory system by a cochlear prosthesis. The present study compared cochlear prosthesis thresholds determined using EMLR with thresholds determined for psychophysical detection and for spike activity in cortical neurons. In systemically deafened guinea pigs, the difference between EMLR and psychophysical threshold level varied, with differences ranging from -4.6 dB (EMLR threshold more sensitive) to +10.7 dB (psychophysical threshold more sensitive) across animals and phase durations. Threshold differences between EMLR and auditory cortex neural spike responses were similar in magnitude and range (-6 to +15 dB) to those seen for EMLR vs. psychophysical thresholds. These ranges are comparable to the behavioral operating range for a given condition. In 3 of 12 subjects, the EMLR was absent for some or all electrode configurations tested, even at levels well above the threshold for psychophysical detection or cortical neuronal response. These results suggest that neither the EMLR thresholds nor cortical neuronal spike thresholds are an adequate substitute for psychophysical measures of threshold. While not sufficient for use in place of psychophysical measures, EMLR threshold level is strongly correlated with psychophysical threshold level across subjects (R(2)=0.82). Interestingly, plots of thresholds vs. phase duration were roughly parallel for psychophysical and EMLR thresholds, in contrast to the divergence of psychophysical and more peripheral (e.g., electrically evoked auditory brainstem response) evoked neural threshold vs. phase duration functions.

Action Potentials↗
PubMed2005

Evaluation of grey-scale standard display function as a calibration tool for diagnostic liquid crystal display monitors using psychophysical analysis.

The digital imaging and communications in medicine (DICOM) standard proposed the grey-scale standard display function (GSDF) as a calibration tool for making the gradation characteristic of a radiographic output image consistent. This is designed in such a manner that the contrast visually recognised by observers (called psychophysical contrast) becomes a constant for all digital driving levels. The DICOM standard calls such an ideal characteristic perceptual linearisation. The psychophysical gradient that can express the psychophysical contrast was introduced for the evaluation of the GSDF using a liquid crystal display monitor. Investigations regarding its ability to yield a constant psychophysical contrast, independent of the digital driving level change and under an actual observation environment, such as for clinical radiographic diagnosis in hospital, were carried out. The psychophysical gradients of the GSDF were obtained for two kinds of observation environment: one was a restricted environment such as in a dark room, under steady-state adaptation, using the sinusoidal grading pattern corresponding to the peak frequency of the human eye response. The other was an actual environment reflecting that encountered during clinical diagnosis in a hospital. As a result, the psychophysical gradient under the restricted environment became almost constant and independent of the change in digital driving level, i.e. perceptual linearisation could be satisfied. Furthermore, under the actual observation environment, the psychophysical gradient decreased gradually with the increase in digital driving level, i.e. the perceptual linearisation could not be satisfied. The percentage decrease in the value of the psychophysical gradient at the maximum luminance area was approximately 60% compared with that at the minimum luminance area. Accordingly, the GSDF is unsuitable as a calibration tool for the liquid crystal display monitor, which will be used in actual clinical diagnosis, as it cannot achieve 'perceptual linearisation' under the actual environment. For the purpose of clinical diagnosis, it is necessary to enlarge the physical gradient of GSDF further in the high digital driving level range (which relates to a high luminance area) to give an approximation that is as close to the idealised form as possible.

Calibration↗
PubMed1986

Motion selectivity in macaque visual cortex. III. Psychophysics and physiology of apparent motion.

We have conducted physiological and psychophysical experiments to identify possible neural substrates of the perception of apparent motion. We used identical sequences of flashed stimuli in both sets of experiments to better compare the responses of cortical neurons and psychophysical observers. Physiological data were obtained from two cortical visual areas, striate cortex (V1) and the middle temporal area (MT). In the previous paper we presented evidence that neuronal thresholds for direction selectivity in extrastriate area MT were similar to psychophysical thresholds for motion perception at the largest effective interflash interval, and thus speed, for a given eccentricity. We now examine physiological and psychophysical thresholds for a broad range of speeds to determine whether such a correspondence exists for speeds below the upper threshold considered in the previous paper. Stimuli were presented in stroboscopic motion of constant apparent speed while the spatial and temporal interflash intervals were systematically varied. For each neuron we measured the largest spatial interval that elicited directionally selective responses at each of several apparent speeds. We calculated the composite performance of neurons in both MT and V1 by averaging the spatial interval necessary for direction selectivity at each apparent speed. We employed the same apparent-motion stimuli for psychophysical experiments with human subjects in which we measured the spatial interval necessary for the perception of motion over a similar range of apparent speeds. We obtained a composite profile of psychophysical performance by averaging thresholds across subjects at each apparent speed. For high apparent speeds, physiological data from MT, but not V1, corresponded closely to the psychophysical data as suggested in the preceding paper. For low apparent speeds, however, physiological data from MT and V1 were similar to each other and to the psychophysical data. It would appear, therefore, that neurons in either V1 or MT could mediate the perceptual effect at low speeds, whereas MT is a stronger candidate for this role at high speeds. We suggest that the neuronal substrate for apparent motion may be distributed over multiple cortical areas, depending upon the speed and spatial interval of the stimulus.

Animals↗
PubMed2006

Spatial four-alternative forced-choice method is the preferred psychophysical method for naïve observers.

H. R. Blackwell (1952) investigated the influence of different psychophysical methods and procedures on detection thresholds. He found that the temporal two-interval forced-choice method (2-IFC) combined with feedback, blocked constant stimulus presentation with few different stimulus intensities, and highly trained observers resulted in the "best" threshold estimates. This recommendation is in current practice in many psychophysical laboratories and has entered the psychophysicists' "folk wisdom" of how to run proper psychophysical experiments. However, Blackwell's recommendations explicitly require experienced observers, whereas many psychophysical studies, particularly with children or within a clinical setting, are performed with naïve observers. In a series of psychophysical experiments, we find a striking and consistent discrepancy between naïve observers' behavior and that reported for experienced observers by Blackwell: Naïve observers show the "best" threshold estimates for the spatial four-alternative forced-choice method (4-AFC) and the worst for the commonly employed temporal 2-IFC. We repeated our study with a highly experienced psychophysical observer, and he replicated Blackwell's findings exactly, thus suggesting that it is indeed the difference in psychophysical experience that causes the discrepancy between our findings and those of Blackwell. In addition, we explore the efficiency of different methods and show 4-AFC to be more than 3.5 times more efficient than 2-IFC under realistic conditions. While we have found that 4-AFC consistently gives lower thresholds than 2-IFC in detection tasks, we have found the opposite for discrimination tasks. This discrepancy suggests that there are large extrasensory influences on thresholds--sensory memory for IFC methods and spatial attention for spatial forced-choice methods--that are critical but, alas, not part of theoretical approaches to psychophysics such as signal detection theory.

Attention↗
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↗
PubMed2001

Failure of central 5-hydroxytryptamine depletion to alter the effect of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on timing performance on the free-operant psychophysical procedure.

RATIONALE: The 5-hydroxytryptamine (5-HT)(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) alters temporal differentiation of behaviour on the free-operant psychophysical procedure, displacing the psychophysical curve to the left, thereby reducing the indifference point T(50). However, it is not known whether this effect of 8-OH-DPAT is mediated by an action of the drug at somatodendritic autoreceptors or at postsynaptic receptors. OBJECTIVE: To compare the effects of 8-OH-DPAT on performance on the free-operant psychophysical procedure in normal (sham-lesioned) rats and in rats whose 5-HTergic pathways had been lesioned by means of intra-raphe injections of the selective neurotoxin 5,7-dihydroxytryptamine (5,7-DHT). METHODS: Twelve rats received 5,7-DHT-induced lesions of the median and dorsal raphe nuclei, and twelve received sham lesions. They were trained under the free-operant psychophysical procedure to press two levers (A and B) in 50-s trials, during which reinforcement was provided intermittently for responding on A in the first half and B in the second half of the trial. Percentage responding on B (%B) was recorded in successive 5-s epochs of the trials; logistic psychophysical curves were fitted to the data from each rat for the derivation of timing indices [T(50) (time corresponding to %B=50%) and Weber fraction] following treatment with acute doses of 8-OH-DPAT (25, 50, 100, 200 microg kg(-1), s.c.) and saline (vehicle-alone treatment). Levels of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), noradrenaline and dopamine were measured in forebrain regions after the completion of the experiment. RESULTS: Under the vehicle-alone condition, the lesioned group displayed a greater propensity for switching between the levers, but T(50) and the Weber fraction did not differ between the groups. In both groups, 8-OH-DPAT shifted the psychophysical curve to the left, significantly reducing T(50) at the 200-microg kg(-1) dose; the effect of 8-OH-DPAT did not differ significantly between the groups. Levels of 5-HT and 5-HIAA in the lesioned group were about 10% of those in the sham-lesioned group; there was no effect of the lesion on catecholamine levels. CONCLUSIONS: The results confirm that 8-OH-DPAT disrupts temporal differentiation in the free-operant psychophysical schedule, reducing the indifference time, T(50). The failure of central 5-HT depletion to alter the effect of 8-OH-DPAT suggests that this effect may be mediated by stimulation of postsynaptic 5-HT(1A) (or possibly 5-HT(7)) receptors rather than somatodendritic 5-HT(1A) autoreceptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1982

The influence of probe-tone parameters on the shape of psychophysical tuning curves in normal-hearing listeners.

Psychophysical tuning curves have become increasingly important in furthering the interpretation of traditional masking data. Although a substantial amount of relatively new information is available on psychophysical tuning curves, the analysis and interpretation of this information are difficult because of the lack of consistency among the probe-tone parameters used. This study investigated the shape of psychophysical tuning curves under simultaneous masking as a function of three frequencies--500, 1000, and 4000 Hz; three levels--5, 20, and 40 dB SL; and two durations--10 msec and 200 msec, of the probe tones. The results indicate that the general shape of psychophysical tuning curves is consistent throughout the 18 combinations of parameter values studied. Irregularities such as notches and CF shifts, inconsistently noted in previous investigations, were observed in the shape of psychophysical tuning curves. However, they were shown to depend on unique combinations of probe-tone parameters. These results are compared to previous investigations of simultaneous-masking psychophysical tuning curves with respect to the specific effects of probe-tone parameter values on the shape of the curves. Irregularities in the shape of psychophysical tuning curves are discussed in relation to aural combination tones and other nonlinearities.

Adult↗
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↗
PubMed1999

The psychophysical approach to manual materials handling task design.

For approximately three decades, researchers have utilized psychophysics to develop guidelines (weights, forces and frequencies) for manual materials handling tasks. Early work by Stover Snook and his colleagues provided the foundations of the experimental methodologies that would be used by other researchers as well as design data that would be used by practitioners. Currently, there are extensive psychophysical data for designing a variety of materials handling tasks. The current state of psychophysical data will be examined, and the psychophysical approach will be compared to the biomechanical and physiological approaches to setting limits for materials handling tasks. The advantages and disadvantages of the psychophysical approach will be discussed, as will the research needs required to address the current limitations of the psychophysical approach.

Biomechanical Phenomena↗
PubMed2006

Visual-evoked response, pattern electroretinogram, and psychophysical magnocellular thresholds in glaucoma, optic atrophy, and dyslexia.

PURPOSE: The purpose of this study is to compare visual-evoked response (VEP) pattern electroretinogram (PERG) and psychophysical thresholds to the same stimulus, designed to be optimal for the magnocellular system, in suspects and patients with early glaucoma, patients with optic nerve disease, dyslexic children, and age-matched controls. METHODS: Stimuli were low spatial frequency sinusoidal luminance profile gratings abruptly phase reversing at 7.14 Hz. Electrophysiological recordings were made at 50%, 30%, 20%, 10%, and 5% contrast. Threshold was the lowest contrast evoking a clear response at the stimulus frequency. Three independent judges scored the traces. Psychophysical thresholds were obtained by ascending and descending method of limits. VEPs and PERGs to International Society for Clinical Electrophysiology of Vision (ISCEV) standards and to increasing spatial frequencies were obtained as parvocellular specific controls. Patients were diagnosed independently by the referring professionals. RESULTS: Parvocellular-specific responses were normal, except in cases with explicable visual acuity loss. The judges scores correlated highly (> 0.9). VEPs and PERGs correlated highly and each correlated less well with psychophysics in normals, glaucoma, and dyslexia but the opposite occurred in optic nerve disease. VEPs had the lowest normal values and least variance (all adults < 5%, children < 10%, PERGs < 20%). In glaucoma, VEP magnocellular deficits occurred in 85% of recently diagnosed positive cases, 48% of high-risk suspects, 39% of low-risk suspects, and ocular hypertensives. Approximately 28% of dyslexics had VEP magnocellular deficits. PERG losses were less frequent. There was a clear dichotomy and low correlations between psychophysics and electrophysiology both within and between groups. Psychophysical threshold elevations were absent in all glaucoma groups, often large in optic atrophy and small (2.5%) but highly significant in dyslexia. CONCLUSION: Contrast thresholds to magnocellular-specific stimuli are consistent in cortex and retina. VEPs are more reliable. Psychophysics seems to tap different mechanisms. VEPs are very sensitive to early glaucoma. The lack of VEP loss in dyslexia suggests the other losses are artifactual. Further research is needed to see if stimuli even more like the frequency-doubling technology are more useful clinically.

Adult↗
PubMed2003

Cone selective adaptation influences L- and M-cone driven signals in electroretinography and psychophysics.

To assess the influence of selective adaptation of long (L) and middle (M) wavelength sensitive cones with electroretinography (ERG) and psychophysics, a novel adaptation procedure was developed, which comprises a selective and quantifiable change in the state of adaptation in the different cone types. One adaptation condition was used as a reference. In four additional conditions, the M-cones or the L-cones were selectively adapted, so that they absorbed either more or less photons. At each of these five states of adaptation, the ERG response amplitudes to 30Hz L- and to M-cone selective stimuli were measured. Furthermore, the psychophysical sensitivities to L- and M-cone selective stimuli were measured at different temporal frequencies. In subjects with normal color vision, adaptation can have a strong influence on the L- and M-cone driven response amplitudes in the ERG and on both the L- and the M-cone sensitivities in the psychophysical luminance channel. As a result, the L- to M-cone ERG and psychophysical ratios can change dramatically at the different states of adaptation. The cone sensitivity thresholds and the L- to M-cone sensitivity ratio in the psychophysical chromatic channel are about unity at all states of adaptation, suggesting the presence of a compensatory mechanism. In dichromats, the responses and sensitivities to stimulation of the absent cone type were generally small at all states of adaptation. But, with reddish backgrounds residual ERG responses and residual psychophysical sensitivities were observed, indicating the presence of either a robust rod driven signal or an additional adaptation mechanisms that are not cone driven and that have not been described before.

Adaptation, Ocular↗