Variability Of Threshold Estimates Research Articles

Establishment of ANSI/ASA S3/SC1.6—Standardization of evoked potential hearing test methods in toothed whales

The use of auditory evoked potentials (AEPs) to test the hearing of toothed whales has produced hundreds of toothed whale audiograms over the last two decades. Unfortunately, multiple approaches to obtaining AEP audiograms have been employed, including different methods for estimating the hearing threshold, the use of different acoustic test stimuli, different approaches to calibration, etc. Lack of methodological consistency has resulted in considerable variability in threshold estimates between researchers and laboratories and conclusions about differences in the hearing abilities of toothed whale populations that are likely erroneous. To address this issue, ANSI/ASA S3/SC1.6-2018 was developed. The document proposes standardized methods for performing AEP hearing tests in toothed whales. Implementation of the standard should reduce variability in threshold estimates obtained by different laboratories and researchers and make the resulting audiograms more comparable. Although AEP hearing tests are common for the clinical assessment of hearing in stranded whales and their use for this purpose is not substantially impacted by methodological variances, audiogram comparability is necessary for the broader implementation of AEP audiograms into environmental impact assessments and regulation. Thus, the standard should facilitate environmental stewardship efforts to manage the impact of anthropogenic sound on marine mammals.The use of auditory evoked potentials (AEPs) to test the hearing of toothed whales has produced hundreds of toothed whale audiograms over the last two decades. Unfortunately, multiple approaches to obtaining AEP audiograms have been employed, including different methods for estimating the hearing threshold, the use of different acoustic test stimuli, different approaches to calibration, etc. Lack of methodological consistency has resulted in considerable variability in threshold estimates between researchers and laboratories and conclusions about differences in the hearing abilities of toothed whale populations that are likely erroneous. To address this issue, ANSI/ASA S3/SC1.6-2018 was developed. The document proposes standardized methods for performing AEP hearing tests in toothed whales. Implementation of the standard should reduce variability in threshold estimates obtained by different laboratories and researchers and make the resulting audiograms more comparable. Although AEP hearing tests are commo...

Thermal Perceptual Thresholds are typical in Autism Spectrum Disorder but Strongly Related to Intra-individual Response Variability

Individuals with autism spectrum disorder (ASD) are often reported to exhibit an apparent indifference to pain or temperature. Leading models suggest that this behavior is the result of elevated perceptual thresholds for thermal stimuli, but data to support these assertions are inconclusive. An alternative proposal suggests that the sensory features of ASD arise from increased intra-individual perceptual variability. In this study, we measured method-of-limits warm and cool detection thresholds in 142 individuals (83 with ASD, 59 with typical development [TD], aged 7–54 years), testing relationships with diagnostic group, demographics, and clinical measures. We also investigated the relationship between detection thresholds and a novel measure of intra-individual (trial-to-trial) threshold variability, a putative index of “perceptual noise.” This investigation found no differences in thermal detection thresholds between individuals with ASD and typical controls, despite large differences between groups in sensory reactivity questionnaires and modest group differences in intra-individual variability. Lower performance IQ, male sex, and higher intra-individual variability in threshold estimates were the most significant predictors of elevated detection thresholds. Although no psychophysical measure was significantly correlated with questionnaire measures of sensory hyporeactivity, large intra-individual variability may partially explain the elevated psychophysical thresholds seen in a subset of the ASD population.

Objective methods to measure vestibular evoked myogenic potential response saccular tuning curves

Objective: To detect cervical vestibular evoked myogenic potential (cVEMP) responses using objective statistical approaches and to apply this approach to estimate saccular frequency-tuning curves in volunteers and Ménière’s disease (MD) patients.Design: Estimates of cVEMP threshold were carried out by 3 expert raters at 500 Hz and compared to objective threshold estimates (using Hotelling’s T2 [HT2] and Fsp). Saccular tuning curves were objectively estimated.Study sample: Objective and subjective estimates of cVEMP response thresholds were compared for 13 normal hearing adults. Objective measurement of saccular tuning curves was explored in 20 healthy adults and 15 patients with MD.Results: Significant variability was seen between subjective estimates of cVEMP thresholds. Objective analysis with the HT2 test was more sensitive than 2 of 3 experts in detecting responses. The measurement time of cVEMP was considerably reduced with the HT2 test. Objective saccular tuning curves in volunteers showed strongest responses at 500 Hz. A flatter tuning curve was seen for MD patients.Conclusions: There is significant variability in subjective estimations of cVEMP thresholds. Objective analysis methods are more sensitive than subjective analysis, can detect responses rapidly and have potential to reduce variability in threshold estimates, hence they appear well suited to measure cVEMP tuning curves.

Experience with a yes-no single-interval maximum-likelihood procedure.

The report in 1993 by Green [J. Acoust. Soc. Am. 93, 2096-2105 (1993)] describing the application of a new psychophysical method requiring few trials and little time to measure auditory thresholds has generated considerable interest among experimentalists. The procedure uses a single-interval stimulus presentation, requests a yes-no decision by subjects, and implements a maximum-likelihood calculation to determine the next trial stimulus level within an adaptive track, as well as the final threshold estimate. Data are presented here describing separate experiences with this procedure in two laboratories in both detection and discrimination tasks. Issues addressed include comparisons with more traditional psychophysical methods, variability in threshold estimates, experimental time required, and possible minor modifications to improve the basic procedure. Results using this procedure are comparable in terms of variability of estimates to those emerging from more lengthy procedures. However, because it may be difficult for some listeners to maintain a consistent criterion and because attentional lapses may be costly, experimenters must be willing to monitor performance closely and repeat some tracks in cases where excessively high variability is noted. Further, this procedure may not be suitable for tasks for which the form of the psychometric function is not well-established. Modifications allowing a variable slope parameter in the maximum-likelihood evaluations of psychometric functions may be of benefit.

Visual field test simulation and error in threshold estimation.

To establish, via computer simulation, the effects of patient response variability and staircase starting level upon the accuracy and repeatability of static full threshold visual field tests. Patient response variability, defined by the standard deviation of the frequency of seeing versus stimulus intensity curve, is varied from 0.5 to 20 dB (in steps of 0.5 dB) with staircase starting levels ranging from 30 dB below to 30 dB above the patient's threshold (in steps of 10 dB). Fifty two threshold estimates are derived for each condition and the error of each estimate calculated (difference between the true threshold and the threshold estimate derived from the staircase procedure). The mean and standard deviation of the errors are then determined for each condition. The results from a simulated quadrantic defect (response variability set to typical values for a patient with glaucoma) are presented using two different algorithms. The first corresponds with that normally used when performing a full threshold examination while the second uses results from an earlier simulated full threshold examination for the staircase starting values. The mean error in threshold estimates was found to be biased towards the staircase starting level. The extent of the bias was dependent upon patient response variability. The standard deviation of the error increased both with response variability and staircase starting level. With the routinely used full threshold strategy the quadrantic defect was found to have a large mean error in estimated threshold values and an increase in the standard deviation of the error along the edge of the defect. When results from an earlier full threshold test are used as staircase starting values this error and increased standard deviation largely disappeared. The staircase procedure widely used in threshold perimetry increased the error and the variability of threshold estimates along the edges of defects. Using earlier data, when available, overcomes this problem and reduces examination time.

A maximum-likelihood method for measuring binaural lateralization

The maximum-likelihood method is an adaptive psychophysical method. Previous work has outlined this procedure for signal detection tasks using either forced-choice [Green, J. Acoust. Soc. Am. 87, 2662–2674 (1990)], or Yes–No procedures [Green, J. Acoust. Soc. Am. 93, 2096–2105 (1993)]. The current study extends the maximum-likelihood procedure to lateralizing a 500-Hz tone and a sinusoidally amplitude modulated (SAM) signal with a 50-Hz modulation rate and a 3.5-kHz carrier. It is shown that by the sixth trial of the experimental run, an unbiased estimate of threshold may be obtained. Simulations show this procedure to produce less variable and less biased threshold estimates than the Up–Down methods. Data from human observers and from simulations show a theoretically ideal reduction in variability of threshold estimates with increasing number of trials. [Work supported by NIH and AFOSR.]

Estimating Thresholds in Conventional and High-Pass Resolution Perimetry Using Computer Simulation

High-pass resolution perimetry is a new technique that uses a vanishing optotype as the test stimulus. This type of stimulus is thought to produce steeper frequency-of-seeing curves than the stimulus used in conventional automated perimetry, resulting in a lower variability in threshold estimates. The purpose of this study was to compare the stimulus properties in both conventional and high-pass resolution perimetry in computer simulation experiments. The computer model contained stimulus-response data sets obtained from frequency-of-seeing experiments in 11 normal subjects tested with each perimetric technique at four retinal locations [(0 degrees , 30 degrees ), (0 degrees , 15 degrees ), (0 degrees , - 15 degrees ), and (0 degrees , - 30 degrees )]. We programmed eight staircase procedures varying from a coarse one with one reversal to an elaborate procedure with four reversals to look at the relationship between accuracy (the difference between the estimated and actual threshold) and efficiency (number of presentations required for estimate) with each technique. Threshold estimates were made 100 times for each location, strategy, perimetric technique, and subject. Our results showed that an increase in accuracy was always coupled with a decrease in efficiency and that the relationship between these two parameters was similar between the two techniques. Some evidence, however, is presented to show that compared to conventional perimetry relatively simple staircase procedures may be used with high-pass resolution perimetry to attain threshold estimates of similar accuracy.

Stimulus step size and heterogeneous stimulus conditions in adaptive psychophysics

This paper reports on simulations of repeated estimates of stimulus thresholds using a two-down, one-up adaptive procedure and forced-choice procedures using 2, 3, and 4 response alternatives. In the first section of the paper, the selection of an initial and final step size for the stimulus is the main focus. For a 2-alternative forced-choice psychometric function, a step size of roughly one-quarter the useful range (60%–90%) provides a reasonable initial step size. A final step size of roughly half that value is recommended. The increase in the variability of threshold estimates is, however, not very great if values near those recommended are selected instead. The change in the variability of the threshold estimates with the change in the number of alternatives used in the forced-choice procedure can be predicted by considering the sweat factor associated with the psychometric function. In the second part of the paper, the focus is on how the variability in threshold estimates increases if the stimulus set is heterogeneous; that is, the stimuli produce different psychometric functions. Stimuli that differ only in their means increase the variability of threshold estimates more than do stimuli that differ only in the slopes of their psychometric functions. Stimuli that contain both forms of heterogeneity, however, increase the variability in threshold estimates by only about 50%.

Temporal Resolution in Children

The auditory temporal resolving power of young children was measured using an adaptive forced-choice psychophysical paradigm that was disguised as a video game. 20 children between 3 and 7 years of age and 5 adults were asked to detect the presence of a temporal gap in a burst of half-octave-band noise at band center frequencies of 400 and 2,000 Hz. The minimum detectable gap (gap threshold) was estimated adaptively in 20-trial runs. The mean gap thresholds in the 400-Hz condition were higher for the younger children than for the adults, with the 3-year-old children producing the highest thresholds. Gap thresholds in the 2,000-Hz condition were generally lower than in the 400-Hz condition and showed a similar age effect. All the individual adaptive runs were "adult-like," suggesting that the children were generally attentive to the task during each run. However, the variability of threshold estimates from run to run was substantial, especially in the 3-5-year-old children. Computer simulations suggested that this large within-subjects variability could have resulted from frequent, momentary lapses of attention, which would lead to "guessing" on a substantial portion of the trials.

The reliability of auditory thresholds in the 8- to 20-kHz range using a prototype audiometer.

This study was designed to evaluate both intra- and intertester reliability of auditory thresholds in the 8- to 20-kHz range using a recently developed high-frequency audiometer [Stevens et al., J. Acoust. Soc. Am. 81, 470-484 (1987)]. With this device, signals from a high-frequency transducer are introduced into the ear canal via a plastic tube. A calibration function is calculated for each ear and used to estimate the sound-pressure level (SPL) at the tympanic membrane. Twenty normal-hearing listeners were tested four times, twice by each of two examiners. In the higher frequencies, accurate calibration functions could not be obtained for many subjects; in these cases, values extrapolated from lower frequencies were used to estimate SPL. Findings reveal that the standard error of measurement for both intra- and intertester measures increases as a function of frequency. Intertester variability was only slightly higher than intratester variability. In most cases, variability of threshold estimates in dB SPL was higher than that observed for the uncorrected attenuator settings. Exclusion of extrapolated values improved reliability substantially.