Psychophysical exponents for single papillae: A comparison with whole-mouth exponents

Taste intensity judgments in response to chemical stimulation of single human fungiform papillae were obtained by the method of magnitude estimation. Intensity scales constructed from these data were compared to those obtained from the same subjects in response to stimulation of the whole mouth. Single papilla functions conformed well to the power law governing the growth of sensation magnitude, although a minority of single papilla functions exhibited peaking of response magnitude at intermediate concentrations, followed by a decline in response magnitude at higher concentrations. Single papilla exponents were found to be lower than whole mouth exponents and were positively correlated with detection and/or recognition thresholds of the papillae for most compounds. Exponents of summated single papilla functions were greater than median single papilla exponents, but their relative magnitude vs. whole mouth exponents varied by test compound. The data were discussed in relationship to previous findings concerning flow rate effects, threshold-exponent relationships across the tongue surface, and level-dependent spatial summation.     

On predicting exponents for cross-modality matches

Mashhour and Hosman used magnitude estimations to scale seven continua: line length, time duration, finger span, loudness of noise, weight, gray reflectance, and surface area. The first four continua also served as the adjusted stimuli in 17 cross-modality matches among the various continua. Contrary to the view expressed by Mashhour and Hosman, the results appear to support the psychophysical power law. A reanalysis of the data shows that the exponents of the power functions obtained in cross-modality matches agree with the exponents of the power functions produced by magnitude estimations, provided correction is made for the regression effect. The measured discrepancies between the exponents predicted and those actually obtained show scatter that is consistent with that of other experiments. In particular, the scatter accords well with the distribution of 68 exponents predicted by Moskowitz from experiments in which Os matched both number and loudness to various taste concentrations.     

Consistency of individual exponents in cross-modal matching

An important question about individual differences in the exponent of the psychophysical power law is how they should be interpreted. The differences may reflect permanent characteristics of individuals, and it has been argued that, if this is so, the range of these differences is so great as to identify the class of data as exceptional among the physical and biological sciences. Cited as evidence of such permanence has been the correlation between individual exponents obtained on two separate occasions. In a previous paper, we showed that increasing the time interval between occasions reduced the correlation to a nonsignificant level; we argued, therefore, that obtained individual differences in exponents, even though large, depended upon the operation of factors only incidentally associated with the particular observer. In a series of new studies of session-to-session correlation between individual exponents, we provide evidence that: (1) our original finding for magnitude estimates of visual size is repeatable, with the correlation dropping to nearly zero after 1 week; (2) when judged line length is matched to brightness, a delay of I week is sufficient to produce a nonsignificant correlation; (3) in contrast, magnitude estimates of loudness yield significant correlations after a week’s delay; (4) but, when moduli are arbitrarily changed between sessions by the experimenter, these correlations for magnitude estimates of loudness drop to a nonsignificant level, even for a zero-delay condition. We conclude that, whereas in some scaling tasks the passage of time alone between sessions is sufficient to disrupt what appears to be the mnemonic basis for session-to-session correlation, in other (less familiar) tasks, more positive interference (in the form of a modulus change) is needed to achieve the same end. The evidence is consistent with the belief that enduring characteristics of the observer contribute only a small portion of the variability in individual power law exponents.     

Biasing power law exponents by magnitude estimation instructions

This study investigates the influence of attention loading on the established intersensory effects of passive bodily rotation on choice reaction time (RT) to visual motion. Subjects sat at the center of rotation in an enclosed rotating chamber and observed an oscilloscope on which were, in the center, a tracking display and, 10° left of center, a RT line. Three tracking tasks and a no-tracking control condition were presented to all subjects in combination with the RT task, which occurred with and without concurrent cab rotations. Choice RT to. line motions was inhibited (p < .001) both when there was simultaneous vestibular stimulation and when there was a tracking task; response latencies lengthened progressively with increased similarity between the RT and tracking tasks. However, the attention conditions did not affect the intersensory effect; the significance of this for the nature of the sensory interaction is discussed.     

Bias effects on magnitude and ratio estimation power function exponents

A bias model of relative judgment was used to derive a ratio estimation (RE) power function, and its effectiveness in providing estimates of exponents free of the effects of standards was evaluated. The RE bias model was compared with the simple RE power function that ignores bias. Results showed that when bias was not taken into account, estimates of exponents exhibited the usual effects of standards observed in previous research. However, the introduction of bias parameters into the RE power function virtually eliminated these effects. Exponents calculated from "equal-range segments" (e.g., low stimulus range vs. high stimulus range) judged by magnitude estimation (ME) were examined: the effects of equal-range segments on exponents were much stronger for ME than standards were for RE, using the bias model.     

Constancy of individual exponents for category production of inspired lung volume

Individual exponents for production of inspired lung volume were compared both within experimental sessions (after a delay of 5 to 10 min.) and between sessions (after a delay of 1 yr.). Reliable correlations were observed between pairs of individual exponents regardless of the time elapsed between repetitions of the task. Constancy of exponents may reflect a propensity for subjects to respond in characteristic ways to psychophysical scaling tasks.     

Detection of long‐range dependence and estimation of fractal exponents through ARFIMA modelling

We evaluate the performance of autoregressive, fractionally integrated, moving average (ARFIMA) modelling for detecting long‐range dependence and estimating fractal exponents. More specifically, we test the procedure proposed by Wagenmakers, Farrell, and Ratcliff , and compare the results obtained with the Akaike information criterion (AIC) and the Bayes information criterion (BIC). The present studies show that ARFIMA modelling is able to adequately detect long‐range dependence in simulated fractal series. Conversely, this method tends to produce a non‐negligible rate of false detections in pure autoregressive and moving average (ARMA) series. Generally, ARFIMA modelling has a bias favouring the detection of long‐range dependence. AIC and BIC gave dissimilar results, due to the different weights attributed by the two criteria to accuracy and parsimony. Finally, ARFIMA modelling provides good estimates of fractal exponents, and could adequately complement classical methods, such as spectral analysis, detrended fluctuation analysis or rescaled range analysis.     

Critical bands and mixed-frequency scaling: sequential dependencies, equal-loudness contours, and power function exponents

Stimuli of random intensities and various but predictable frequencies were presented for repeated magnitude estimations on the same scale (mixed-frequency scaling). The frequencies for a particular judgment session were selected so that they lay either inside each other's critical bands or outside them. Contrastive dependencies of current magnitude estimation responses on previous stimuli of a different frequency were significantly affected by whether the two frequencies were inside or outside each other's critical bands, while assimilative dependencies were not. This reinforces the idea that such dependencies are sensory in nature and arise from a different mechanism than do the assimilative dependencies. Mixed-frequency scaling of loudness also gives rise to cross-frequency matching functions from which equal-loudness contours can be calculated. These contours calculated from the present judgments are similar to those produced from other methods, even when they are extrapolated to untested intensities. Power function exponents for loudness scaled in this way are larger for lower frequencies, as has been found in previous studies, and are consistent with the flattening of the calculated equal-loudness contours for low frequencies as intensity increases.     

Constancy of individual exponents for inspired lung volume: a comment on Harver (1987)

In this paper we made two brief commentaries on Harver's (1987) experiment. The first comment is an observation on the growing area of respiratory psychophysics for which we prefer the name Behavioral Physiology. In the second comment it is suggested that the stable individual differences in the exponent of the psychophysical power law reported by Harver may be an artifact of the psychophysical method employed: category production.