Critical Notice

N oll , R ichard . The Jung Cult: Origins of a Charismatic Movement.
N oll , R ichard . The Aryan Christ: The Secret Life of Carl Jung.     

Temporal summation related to the nature of the proximal stimulus for the warmth sense

Magnitude estimations of the warmth aroused by radiant stimulation of the forehead showed that warmth obeys the psychophysical power law when the’ duration of the stimulus is relatively long (3 or 6 sec). When duration is short (0.25, 0.5. or 1 sec), however, warmth grows as a more complex function of irradiation. The family of psychophysical functions measured for the various durations can be used to generate the rules by which radiant intensity and duration trade to preserve constant warmth. These rules vary systematically from complete temporal summation (i.e., complete reciprocity) near threshold to less and less complete summation as warmth level increases. When, however, the stimulus is expressed as an equivalent change of temperature in the skin, there is no summation, only adaptation. It can be shown that temporal summation observed psychophysically must result from the heat-transfer properties of skin tissue.     

Brightness function: Role of the pupil

Pairs of brightness functions were generated by magnitude estimation, one pair for each of three flash durations (0.5,1.0, and 3.0 sec). Each pair comprised a function obtained with an artificial pupil and a function obtained with the uncontrolled natural pupil. The pupil turned out to have little or no effect on the form and slope of the power functions for brightness, even when flash duration was as long as 3.0 sec.     

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.     

Brightness function: Binocular versus monocular stimulation

A dozen observers matched numbers to the apparent brightness of a target viewed by one eye or by both eyes. Brightness grew as a power function of luminance, and the functions were practically identical for the two modes of viewing. Throughout its course, the obtained binocular function tended to fall about a decibel above the monocular function. This small degree of binocular summation, of the order of a jnd, mayor may not be significant.     

Brightness and loudness as functions of stimulus duration

The brightness of white light and the loudness of white noise were measured by magnitude estimation for sets of stimuli that varied in intensity and duration. Brightness and loudness both grow as power functions of duration up to a critical duration, beyond which apparent magnitude is essentially independent of duration. For brightness, the critical duration decreases with increasing intensity, but for loudness the critical duration is nearly constant at about 150 msec. Loudness and brightness also grow as power functions of intensity. The loudness exponent is the same for all durations, but the brightness exponent is about half again as large for short durations as for long. The psychophysical power functions were used to generate equal-loudness and equal-brightness functions, which specify the combinations of intensity E and duration T that produce the same apparent magnitude. Below the critical duration ET equals k for equal brightness, and ET^a equa Is k for equal loudness. The value a is about 0.7 for threshold and about 1.25 for supraliminal loudness.     

Individual brightness functions

A total of 34 individual brightness functions were measured for 18 observers by two different methods. In one method the observer set various luminance levels of a white target and assigned numbers proportional to the apparent brightness of the levels set. In the other method the observer adjusted the loudness of a white noise and the luminance of a white target in order to achieve a series of cross-modality matches between loudness and brightness. Both methods gave good approximations to power functions, showing that the psychophysical power law holds for the individual perceiver.     

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.     

Variability of olfactory threshold and its role in assessment of aging

Olfactory thresholds of elderly persons (over 65 years) average one to two orders of magnitude higher than those of young adults (under 30 years). Past studies reveal enormous spreads (typically about three orders of magnitude) of individual thresholds within each age group and extensive overlap between the two groups—enough to question how typically decline in sensitivity characterizes the individual aged person. The present study shows that much of the observed overlap is misleading, because the brief threshold tests usually administered tend to exaggerate individual differences. A more representative assessment of an individual’s threshold (for 1-butanol) was achieved by averaging the thresholds from two to eight separate short tests, spread over 4 days. The spread of each group’s thresholds (12 young and 12 elderly subjects) narrowed strikingly as the number of tests averaged increased from one to four; further tests accomplished no additional narrowing of spread. Based on a single test, thresholds of young and elderly overlapped in the usual way; but based on four or more tests, thresholds of young and elderly overlapped little or not at all. The outcome (1) argues that decline in smell sensitivity seems to be, after all, a common feature of aging, and (2) sheds light on the sourcesof variability of sensory thresholds.