The form of the psychophysical function near threshold

Psychophysical functions typically depart from a simple power law in the vicinity of the absolute threshold. Five versions of the psychophysical power law have been proposed to describe the function near threshold. An account is given of some of the difficulties encountered in attempts to decide among the various versions by means of empirical tests.     

Odor intensity: Differences in the exponent of the psychophysical function

A series of five experiments showed that there are reliable differences among the exponents of the psychophysical power functions for odorants. There was virtually a perfect rank-order correlation between the size of the exponent and the water-solubility of the odorants. The exponents for odorants that are completely soluble in water (n-propanol and acetone) were approximately 2.5 times the size of the exponents for odorants that are insoluble in water (n-octanol and geraniol). For n-aliphatic alcohols, the size of the exponent and solubility in water decrease as a function of carbon chain-length. Although the exponents were higher when the stimuli were delivered with an air-dilution olfactometer than when they were sniffed from cotton swabs, the relative values among odorants were independent of the method of stimulus presentation.     

Empirical evaluation of a model of global psychophysical judgments: III. A form for the psychophysical function and intensity filtering

In part I, a concept of ratio estimation is defined and it is shown that if such estimates depend only upon the physical ratio of the signal to the reference signal, the psychophysical function must be a power function. Assuming the same exponents for each component, an invariance condition, equivalent to a sum of power functions, is studied empirically for binaural loudness. It is fully or partially sustained for 19 of 22 respondents. Since failures may be attributable to different exponents in the two ears, the ratio of the two exponents is estimated but that fails to explain the failures. Other possible explanations are suggested. In part II, an intensity filtering model is presented, accounting for the phenomenon where monaural loudness matches show a bias depending on the matching ear. We show (a) that the existence of such a bias does not alter the prior experimental results; and (b) assuming the power function, that five respondents attenuate the opposite ear and two enhance it.     

Mechanisms for categorization: Decision criteria and the form of the psychophysical function

The essential features that any satisfactory model of categorical judgement must account for are discussed. The implications of the strong evidence for the Thurstone case V model are drawn out. Then evidence for a linear learning model of criterion setting is presented including new data for isobias functions with either response speed deadlines or physical stimulus difference manipulated. A method for extending linear learning models to encompass joint setting of several criteria is suggested. It is shown that an arcsinh transformation of the Thurstone scale produces a scale which is a linear function of stimulus intensity in decibels. The scale parameter of this transformation remains constant for stimulus ranges greater than 18 dB while changing systematically when sequential presentation is manipulated to improve discrimination.     

Effects of acute bouts of exercise on cognition

A review was conducted of studies that assessed the effects of acute bouts of physical activity on adults' cognitive performance. Three groups of studies were constituted on the basis of the type of exercise protocol employed. Each group was then evaluated in terms of information-processing theory. It was concluded that submaximal aerobic exercise performed for periods up to 60 min facilitate specific aspects of information processing; however, extended exercise that leads to dehydration compromises both information processing and memory functions. The selective effects of exercise on cognitive performance are explained in terms of Sanders' [Acta Psychol. 53 (1983) 61] cognitive-energetic model.     

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.     

Effects of arachidonic acid on the spatial cognition of aged rats

Abstract:  To examine the effects of arachidonic acid (AA) on age-related cognitive deficits, Fischer 344 rats were given an AA-supplemented powder diet for 12 weeks from 18.6 months old as part of the old AA (OA) group. Other age-matched rats were fed a non-AA-supplemented powder diet as part of the old control (OC) group, and young rats were fed lab pellets as part of the young control (YC) group. When the aged rats reached 20.0 months old, all animals were tested for spontaneous activity in an open field, followed by the Morris water maze place and cue tasks. Escape latencies for the place task showed that the YC rats were fastest, and there was no difference between the OA and OC groups. However, the probe test and the first block of the cue task indicated that the OA rats remembered the location of an invisible platform better than the OC rats. Although the amount of hippocampal AA was larger in the OA rats than in the OC rats, the difference was not significant. The results showed that AA administration to aged animals may alleviate age-related deficits in spatial cognition.     

A note on psychophysical measures

The nature of liminal measurement is discussed, and the standard deviation is proposed asa suitable alternative measure to the limen.     

Effects of exposure to psychophysical scaling on lingual vibrotactile magnitude estimation and magnitude production

The purpose of the present study was to determine if the results obtained by the scaling methods of magnitude estimation and magnitude production could be influenced by providing subjects with prior exposure to psychophysical scaling in the form of magnitude estimation or magnitude production. Group 1 (n = 10, Mage = 21.1 yr.) performed lingual vibrotactile-magnitude estimation followed by lingual vibrotactile magnitude production. Group 2 (n = 10, Mage = 19.7 yr.) performed lingual vibrotactile-magnitude production (using the magnitude-estimation responses provided by Group 1), followed by lingual vibrotactile-magnitude estimation. For the magnitude estimations there was no over-all statistically significant difference between the two groups, but there was for the magnitude-production values. Magnitude-estimation scaling was apparently not influenced by prior exposure to magnitude production, while magnitude-production scaling was influenced by prior exposure to magnitude estimation. The results are discussed in terms of how subjective scaling behavior in psychophysical experimentation may be influenced by the interaction between an absolute internal scaling mechanism and parameters set by the experimenter, such as scaling method and range of stimulus intensity.     

Concerning the psychophysical power law

It is fortunate that, despite our theorizings, most of our facts manage to stay stubbornly as they were. I am encouraged by that thought as it bears on a recent theoretical attempt by Treisman (1964) to do over the psychophysical law. I should like, more in explication than in rebuttal, to comment on three major points relating to the law in question.     

A note on multidimensional psychophysical analysis

On viewing Thurstone's psychophysical scale from the point of view of the mathematical theory of one-parameter continuous groups, it is seen that a variety of different psychological or statistical assumptions can all be made to lead to a scale possessing similar properties, though requiring different computational techniques for their determination. The natural extension to multi-dimensional scaling is indicated.     

The effect of the induction of involvement on psychophysical judgments

The present investigation was based on the concept of invariance, which holds that identical principles govern the judgment of stimuli arrayed on both physically and socially defined scales. Two experiments were conducted in which involvement was manipulated through the use of instructions presented in conjunction with category judgments obtained in a training session. This was followed by an anchor session. Experiment 1 employed a series of weights as stimuli, while Experiment 2 used random pattern dot slides. The experiments were similar, except for the inclusion of two additional features in the weight study. These were: (1) positive feedback, introduced as an independent variable between the judgment sessions and tested for its effect as an enhancer of involvement; and (2) two stimuli in the anchor session not part of the original stimulus series. These weights provided a test for the generality of involvement set. Among various hypotheses tested in both studies was the expectancy that the introduction of involvement associated with the formation of a judgment scale would lessen the impact of an anchor on judgment. This expectancy was based on the observed effects of involvement in social judgment contexts. Results of both experiments supported the judgment maintenance hypothesis.