Fast and accurate measurement of taste and smell thresholds using a maximum-likelihood adaptive staircase procedure.

This paper evaluates the use of a maximum-likelihood adaptive staircase psychophysical procedure (ML-PEST), originally developed in vision and audition, for measuring detection thresholds in gustation and olfaction. The basis for the psychophysical measurement of thresholds with the ML-PEST procedure is developed. Then, two experiments and four simulations are reported. In the first experiment, ML-PEST was compared with the Wetherill and Levitt up-down staircase method and with the Cain ascending method of limits in the measurement of butyl alcohol thresholds. The four Monte Carlo simulations compared the three psychophysical procedures. In the second experiment, the test-retest reliability of MLPEST for measuring NaCl and butyl alcohol thresholds was assessed. The results indicate that the ML-PEST method gives reliable and precise threshold measurements. Its ability to detect malingerers shows considerable promise. It is recommended for use in clinical testing.     

Tracking of nociceptive thresholds using adaptive psychophysical methods

Psychophysical thresholds reflect the state of the underlying nociceptive mechanisms. For example, noxious events can activate endogenous analgesic mechanisms that increase the nociceptive threshold. Therefore, tracking thresholds over time facilitates the investigation of the dynamics of these underlying mechanisms. Threshold tracking techniques should use efficient methods for stimulus selection and threshold estimation. This study compares, in simulation and in human psychophysical experiments, the performance of different combinations of adaptive stimulus selection procedures and threshold estimation methods. Monte Carlo simulations were first performed to compare the bias and precision of threshold estimates produced by three different stimulus selection procedures (simple staircase, random staircase, and minimum entropy procedure) and two estimation methods (logistic regression and Bayesian estimation). Logistic regression and Bayesian estimations resulted in similar precision only when the prior probability distributions (PDs) were chosen appropriately. The minimum entropy and simple staircase procedures achieved the highest precision, while the random staircase procedure was the least sensitive to different procedure-specific settings. Next, the simple staircase and random staircase procedures, in combination with logistic regression, were compared in a human subject study (n = 30). Electrocutaneous stimulation was used to track the nociceptive perception threshold before, during, and after a cold pressor task, which served as the conditioning stimulus. With both procedures, habituation was detected, as well as changes induced by the conditioning stimulus. However, the random staircase procedure achieved a higher precision. We recommend using the random staircase over the simple staircase procedure, in combination with logistic regression, for nonstationary threshold tracking experiments.     

Obtaining maximum-likelihood estimates of factor loadings and communalities using an easily implemented iterative computer procedure

This paper considers the problem of computing estimates of factor loadings, specific variances, and communalities for a factor analytic model. The equations for maximum-likelihood estimators are discussed. Iterative formulas are developed to solve the maximum-likelihood equations and a simple and efficient method of implementation on a digital computer is described. Use of the iterative formulas and computing techniques for other estimators of factor loadings and communalities is also considered to provide a very general approach for this aspect of factor analysis.     

Ratio scaling of taste intensity by a matching procedure

Given the assumptions that the taste sense is analytic and that the total perceived intensity of a complex taste equals the sum of the perceived intensities of the components, a new procedure was devised to scale taste intensity. Subjects matched the intensity of test substances either to the total intensity or to the intensity of one component of two-component mixtures tin which the two components appeared equally intense. Given the above-stated assumptions, such a pair of matches should define a psychological ratio of 2∶1. Scales erected by this procedure agreed well with scales determined by magnitude estimation.     

Loss of smell and taste within the scope of vitamin B 12 deficiency

The article deals with the case of a patient who had a partial gastrectomy and developed a vitamin B12 deficiency syndrome with anemia, myelopathy and complete loss of the senses of taste and smell. Regression of the symptoms followed liberal dosing with vitamin B12.     

Size and reliability of frequency-difference thresholds determined with operant tracking procedure

Auditory frequency discrimination thresholds have been determined by a “tracking procedure” at five frequencies and two intensity levels for a group of four cats. Intra-animal thresholds were found to be quite stable, and there was good inter-animal agreement among three of the four cats. Although quite stable, the tracking thresholds were larger than those which had been obtained using an avoidance procedure. However, because of the several differences between the tracking procedure and avoidance conditioning procedure, no conclusions can be drawn concerning the efficacy of the different types of reinforcement in determining the ultimate limit of the animals' discrimination ability.     

Old-age deficits in the sense of smell as gauged by thresholds, magnitude matching, and odor identification

Twenty elderly subjects (70-90 years old) and 20 young control subjects (18-24 years old) underwent three kinds of olfactory testing: absolute thresholds to three odorants (d-limonene, iso-amyl butyrate, benzaldehyde), magnitude matching of these odorants to salt tastes, and odor identification of 30 common substances. For all three odorants elderly subjects' mean threshold significantly exceeded that of the young by about ninefold for d-limonene, about threefold for benzaldehyde, and about twofold for iso-amyl butyrate. These threshold differences predict approximate concentration differences necessary to arouse the same estimated odor strength above the threshold for the elderly and the young. Young subjects also scored better than the elderly in odor identification, even when subjects were given four alternatives from which to select the correct label. Unimpaired olfactory functioning is uncommon in the elderly; correlational tests show that as a group the young have better olfactory ability and show more interindividual uniformity.     

Electrophysiological measurement during a time-out procedure in stuttering and normal speakers

Eight stuttering and eight normal speaking subjects were given a time-out (TO) procedure during reading. Simultaneous measures of heart rate and galvanic skin response were obtained in order to infer anxiety level during the TO period. Multivariate and univariate analysis of variance procedures indicated that stutterers, when compared to normals, initially relax during a TO period compared to base rate levels. Near the latter part of the TO period stutterers anticipate the onset of speech and become relatively more anxious. This anxiety level increases even more during the actual speech intervals. Normal speakers resent the intrusion of the TO interval and become more anxious during this period.     

Acquired equivalence and distinctiveness of cues using a sensory-preconditioning procedure

In Experiment 1 rats were presented with two flavours, A and B, that were accompanied either by a third common flavour, X, or by two different flavours, X and Y, respectively. An aversion was then established to A, and the extent to which this aversion generalized to B was measured. Stimulus generalization was found to be more marked when A and B had both been presented with the same flavour, X, during pre-exposure than when A and B had been presented with X and Y. In Experiment 2 three target flavours, A, B, and C, were initially presented. In one pre-exposure condition presentations of A and B were accompanied by X, and C was presented alone; in a second condition A and B were presented in isolation, and C was accompanied by X. After an aversion had been established to A, half of the animals in each of the pre-exposure conditions were tested with B, and the remainder were tested with C. In both of the pre-exposure conditions the generalized aversion was more substantial to B than to C. An analysis of these results in terms of the mechanisms that have been supposed to underlie sensory preconditioning is presented.     

The measurement of response force during a lever-press shock-escape procedure in rats

Three albino rats were given extensive exposure to an escape procedure in which shocks were scheduled to occur 30 sec apart. The amount of downward force exerted on the lever was continuously recorded and compared with traditional discrete measurement in which only responses above an arbitrary force threshold were recorded. Subjects typically remained in contact with the lever throughout the shock-free intertrial interval. Shock onset reliably occasioned a brief lurch from and return to the lever, which resulted in a lever-press escape response being recorded. Lever contact, which occupied an average of 90% of session time, showed great stability in force after a brief (e.g., 5-sec) period of instability after each shock terminated. In general, continuous measurement revealed considerably different results than discrete measurements of on-lever behavior. For example, continuous lever contact fluctuating near response threshold was often recorded as discrete responding, and sustained lever contact occurring below response threshold was omitted from discrete measurement.     

Interrelations of perceptual reports of smell,taste and irritance over the near-threshold range,for members of the N-aliphatic monohydric alcohol series

Many compounds are psychophysically complex because they stimulate all three chemical senses; smell, taste, and irritance.3 Interrelations among these three modalities are reported over the near-threshold range, and comparisons are made for three such compounds; methanol, ethanol, and propanol. Eighteen Ss were tested over 16 sessions each under a range of conditions: a combined task condition that approximated normal drinking, in which thresholds for all three modalities were determined simultaneously, and three conditions, in each of which only one threshold in one modality was determined. Pooled results over Ss gave significant shifts in olfactory thresholds between conditions, whereas changes in gustatory and irritant acuity were less marked. Individual results yielded significant correlations between psychophysical behavior and personality measures. Factor analysis of Ss indicated the existence of subgroups of Ss, each typified by different patterns of relative sensitivity over modalities and over alcohols.     

Hardware and software evolution of an adaptive ability measurement system

A software system for the administration of six different strategies of adaptive ability tests in a variety of formats was developed both on a large-scale time-sharing system and on a real-time minicomputer system. Factors influencing both hardware selection and software design are discussed.     

Estimation and visualization of confusability matrices from adaptive measurement data

We present a simple but effective method based on Luce’s choice axiom [Luce, R.D. (1959). Individual choice behavior: A theoretical analysis. New York: John Wiley & Sons] for consistent estimation of the pairwise confusabilities of items in a multiple-choice recognition task with arbitrarily chosen choice-sets. The method combines the exact (non-asymptotic) Bayesian way of assessing uncertainty with the unbiasedness emphasized in the classical frequentist approach.We apply the method to data collected using an adaptive computer game designed for prevention of reading disability. A player’s estimated confusability of phonemes (or more accurately, phoneme-grapheme connections) and larger units of language is visualized in an easily understood way with color cues and explicit indication of the accuracy of the estimates. Visualization of learning-related changes in the player’s performance is considered.The empirical validity of the choice axiom is evaluated using the game data itself. The axiom appears to hold reasonably well although a small systematic violation is observable for the smallest choice-set sizes.     

Reliability of a dichotic consonant-vowel pairs task using an ABX procedure

The present study examined the reliability of a dichotic consonant-vowels (CV) pairs task using an ABX procedure. Twenty-four right-handed subjects (12 females, 12 males) completed a dichotic CV pairs task twice in a test-retest approach. The conventional free-recall or directed-attention procedure was replaced by an ABX procedure, in which participants were required to determine whether a CV heard binaurally was present in a dichotic pair presented on the same trial. Results showed the expected right-ear advantage in dichotic listening for verbal material. However, reliability was not as high as has been reported with a directed-attention procedure. Methods for improving the reliability of the ABX discrimination task are discussed. In addition, the discussion emphasizes the usefulness of the ABX approach for testing clinical populations.     

The establishment of flavor-flavor associations using a sensory preconditioning training procedure

In Experiment 1, rats drank two distinct flavors in sequence during preconditioning; during training, the second of these flavors was paired with a toxin. During testing, there was an aversion to the flavor not directly paired with the toxin. In Experiment 2, the time interval between the two flavors (0, 3, 9, and 27 sec) in the preconditioning phase was varied; learning occurred only if the flavors were separated by 9 sec or less. Experiment 3, using a 60-sec interstimulus interval also did not reveal learning. These results reveal that the temporal gradient for flavor-flavor associative learning is similar to conventional audio-visual sensory preconditioning delay gradients and different from those obtained in flavor-toxicosis experiments. The results are discussed in terms of their critical implication for Revusky's concurrent interference theory of associative learning.     

Validity of adolescents' self-reports of alcohol use and misuse using a bogus pipeline procedure

Past research, particularly in the area of adolescent smoking behavior, has suggested that more valid self-reports of socially undesirable behavior can be obtained when a bogus pipeline procedure is implemented. "Bogus pipeline" refers to a methodology in which subjects are informed that their self-reports can and will be objectively verified by the researcher through a procedure such as a biochemical test. In actuality, no verification takes place. Recent studies using this methodology have produced mixed results. In the current study, a bogus pipeline procedure designed to increase the validity of adolescents' self-reports of alcohol use and misuse was devised and evaluated as part of the pilot work for an alcohol misuse prevention study in southeastern Michigan schools. A total of 291 students in grades seven through nine were tested in the pilot study. Of these, 173 experienced the bogus pipeline approach in which saliva samples were collected, while 118 served as controls. The differences between the two conditions were examined with respect to nine variables concerning alcohol use and misuse. An overall frequency of use index and an overall misuse index were also examined. Two-way analyses of variance (treatment by grade level and treatment by gender) were conducted. The F values for a main effect of treatment ranged from .00 to 1.27 for the 11 variables. None of these was significant at the prespecified alpha level of .20. In addition, there was no interaction of the treatment procedure with either grade level or gender. In the context of a school-based study in which confidentiality was assured, adolescents' self-reports of alcohol use and misuse were not significantly affected by a bogus pipeline procedure.