Frequency recognition in temporal interference tasks: A comparison among four psychophysical procedures

The frequency discrimination of a 20-msec test tone was measured for the same subjects in four psychophysical paradigms: a single-interval procedure, a two-alternative forced-choice procedure, a same-different procedure, and a method-of-adjustment procedure. In each paradigm, the 20-msec test tone was preceded or followed by a 500-msec, 800-Hz interfering tone. The interfering tone occurred 50 or 5 msec before the onset of the test tone (forward interference) or 100 or 5 msec after the offset of the test tone (backward interference). In each of the four paradigms and for each of the interference conditions the value of Δf for the test tone was varied symetrically around 800 Hz to obtain an estimate of the frequency discrimination thresholds. In all psychophysical paradigms except for the single-interval procedure, there were small or no significant differences in observers’ frequency discrimination behavior among the interference conditions. The thresholds for Δf from these conditions were approximately the same as those obtained without an interfering tone. In the single-interval task, when the test tone preceded the interfering tone (backward interference) by 5 msec, an increase in the value of Δf required for discrimination over that required in the other conditions was measured. These results suggest that the effect of backward interference on a target tone does depend on psychophysical procedure.     

Adaptive procedures in psychophysical research

As research on sensation and perception has grown more sophisticated during the last century, new adaptive methodologies have been developed to increase efficiency and reliability of measurement. An experimental procedure is said to be adaptive if the physical characteristics of the stimuli on each trial are determined by the stimuli and responses that occurred in the previous trial or sequence of trials. In this paper, the general development of adaptive procedures is described, and three commonly used methods are reviewed. Typically, a threshold value is measured using these methods, and, in some cases, other characteristics of the psychometric function underlying perceptual performance, such as slope, may be developed. Results of simulations and experiments with human subjects are reviewed to evaluate the utility of these adaptive procedures and the special circumstances under which one might be superior to another.     

On the psychophysical law and estimation procedures in psychophysical scaling

A general formulation of the power law is presented which has two special features: (1) negative exponents are admissible; and (2) the log law is a special limiting case. Estimation procedures, which provide joint estimates of the exponent and the absolute threshold, are derived for the direct ratio scaling methods. A solution is provided for theaveraging problem for ratio production and bisection scaling, two methods generating observations on the physical scale, and Monte Carlo methods are used to evaluate the resulting estimators.     

Adaptive procedures in psychophysical research.

As research on sensation and perception has grown more sophisticated during the last century, new adaptive methodologies have been developed to increase efficiency and reliability of measurement. An experimental procedure is said to be adaptive if the physical characteristics of the stimuli on each trial are determined by the stimuli and responses that occurred in the previous trial or sequence of trials. In this paper, the general development of adaptive procedures is described, and three commonly used methods are reviewed. Typically, a threshold value is measured using these methods, and, in some cases, other characteristics of the psychometric function underlying perceptual performance, such as slope, may be developed. Results of simulations and experiments with human subjects are reviewed to evaluate the utility of these adaptive procedures and the special circumstances under which one might be superior to another.     

The dispersions of estimates of sensitivity obtained from four psychophysical procedures: Implications for experimental design

The dispersions of estimates of sensitivity obtained from the yes-no, two-alternative forced-choice (2AFC), matching-to-sample, and same-different tasks were examined to determine which task would be more appropriate to use in a given experimental context. Consideration was given to the effects of corrections for extreme sampled proportions. These corrections result in biased estimators, and hence the mean-square deviation of the sampled values about the population mean [MSD $(\hat d')$ ], rather than that about the mean of the estimates [VAR16 $(\hat d')$ ]> indicates more completely the extent of the error in the estimator. For barely discriminable events (d′ ? 0.5), the yes-no and 2AFC tasks had the lowest values of MSD $(\hat d')$ . However, for very discriminable events (d′ > 3), the same-different and matching-to-sample tasks had lower values of MSD $(\hat d')$ .     

Vibrotactile masking: A comparison of psychophysical procedures

The amounts of ipsilateral and contralateral masking obtained with a modified psychophysical procedure were compared for vibratory stimuli presented to different body loci. Results of a combined forced-choice localization task and a forced-choice detection task were similar to the results obtained in previous investigations which employed method of limits and two-alternative, temporal forced-choice procedures, respectively. Ipsilateral maskers produced similar amounts of masking in both the detection and localization tasks for fingertip and arm test sites. Contralateral maskers resulted in considerably more masking in the localization task than in the detection task for both fingertip and arm test sites. When large longitudinal distances were introduced between the test stimulus and masker, little masking was evident in either the localization or detection task. It was concluded that the differences in the amount of ipsilateral and contralateral masking obtained with different psychophysical procedures reflect different effects of a masker on the detectable attributes of a test stimulus. Implications of these results for the study of multiple tactile perception were discussed.     

On the use of bisection procedures in animal psychophysical scaling

The ability of bisection procedures to specify the form of the psychophysical scale depends upon the precision of the technique. It is demonstrated that the precision of bisection techniques is a function of the stimulus interval bisected. Consequently, the choice of stimuli in a bisection experiment may predispose the ability of the experiment to distinguish between alternative psychophysical scales. The testing of interval scale properties of derived scales and the assessment of context effects in bisection experiments was also discussed.This material has been reviewed by the Walter Reed Army Institute of Research, and there is no objection to its presentation and/or publication. The opinions or assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the view of the Department of the Army or the Department of Defense.     

Some functional measurement procedures for determining the psychophysical law

Various statistical procedures are ieveloped for determining the psychophysical law within the context of a functional measurement approach to studying stimulus integration in perception. The specific results are limited to additive or multiplicative psychological laws, but the generalization to alternative cognitive algebras is evident. Estimation of parameters of the hypothesized psychophysical law and test of the hypothesis that the row psychophysical law is the same as the column psychophysical law in a two-factor stimulus design is considered for various possible psychophysicaldaws, including linear, polynomial, and power laws.     

Adaptive psychophysical procedures, loss functions, and entropy

In this article, we present a new strategy for locating a point on a psychometric function (threshold determination) for yes-no procedures, called EntFirst. Our results show that it performs better than many existing strategies for estimating the 50% threshold that are commonly used in nonlaboratory settings. We also provide a review of existing algorithms for finding thresholds, with an emphasis on identifying the types of problems for which each algorithm is useful. Finally, we address a number of issues that are not adequately covered in the literature, including choosing an appropriate loss function to evaluate the performance of an algorithm for a given problem.     

A comparison of three adaptive psychophysical procedures using inexperienced listeners

Thresholds for a masked 1-kHz tone were obtained in single sessions from 60 inexperienced listeners. A two-alternative forced-choice procedure was used in conjunction with one of three adaptive psychophysical techniques. These techniques comprised two staircase techniques targeting either 70.7% or 79.4% correct detection (Staircase-71 and Staircase-79), and parameter estimation by sequential testing (PEST), targeting 80% correct detection. Listeners were provided with a rationale for maintaining concentration at weak signal levels. Similar threshold values were obtained from the Staircase-79 and PEST groups in equal numbers of trials. The degree of oscillation in the level of the signal around the value finally chosen as the threshold was comparable for both staircase techniques. Subsequent fixed-level testing did not provide a true indication of the subjects' capabilities. The amount by which percent correct in fixed-level testing differed from expectations based on adaptive testing varied among the techniques. Additional thresholds were obtained in a second session from 30 of the original subjects. Thresholds with both staircase techniques improved by about 1 dB on retest, while thresholds with PEST were constant across sessions. The variability of the data compared well with that from studies involving experienced listeners.     

The psychophysical dimensions of similarity among random shapes

Six psychological dimensions were recovered from similarity judgments of 20 random forms using Kruskal’s nonmetric scaling technique. These were related to 10 physical factors describing the forms by using canonical correlation analysis and rotations of the resulting vectors. Four factors accounted for 2/3 of the variance of the intersection of the physical and psychological spaces for each of 11 Ss. The factors are described as Complexity, Curvature, Curvature Dispersion, and Straight-length Dispers ion. The problem of the proper psychological distance metric is discussed, and individual differences among Ss are analyzed. The results lead to the conclusion that the four major factors found may be good representations of processes occurring in the perceptual system.     

Response elimination: A comparison of four procedures

Four procedures for eliminating an operant response were compared within a multiple schedule. Response reduction was most rapid when reinforcement was provided for a specific alternative response. The decline in responding produced by extinction and differential reinforcement of other behavior was similar. Responding initially increased and then gradually decreased when reinforcers were delivered independently of responding at fixed times. Removal of reinforcement from the alternative-response and DRO procedures did not result in recovery of the target response. However, the shift from response-independent dilivery of reinforcers to extinction caused an initial increase in responding.     

Variations in hand position, cerebral lateralization, and reading ability among right-handed children

A group of 121 right-handed children between the ages of 7 and 9 with a range of hand positions between normal and inverted were assessed for verbal and visuospatial lateralization and reading comprehension. Results indicate that (a) children with a normal hand position tended to be more verbally lateralized than children with nonnormal positions, although the effect was not strong or always consistent, (b) the closer the child was to the normal position, the higher the child's reading scores, and (c) poor readers were as lateralized for verbal and visuospatial functions as were good readers. Coupled with the results of previous research, these findings suggest that hand position indexes both maturation and lateralization, and that the relationship between hand position and reading is primarily mediated by the former.