Hand-grip strength, measured by a hand dynamometer, was compared with hand preference for writing in a sample of 173 male and female undergraduate students. Hand preference and performance correlated significantly, but superiority of hand grip for 24% of the subjects did not coincide with the preferred hand. Hand-grip performance was not an accurate predictor of hand preference, and neuropsychological inferences on the basis of hand performance should be made cautiously. No significant differences were found between the right/left ratio scores for males and females, or order conditions.

Foveal increment thresholds were measured in young, middle-aged, and older observers. These thresholds, which involved the detection of a small test flash as a function of the intensity of a larger background adapting field (AF), were measured at the instant of onset of the AF (transient condition) and when the eye had been fully light adapted to the AF (steady-state condition). All stimuli were presented to the left eye in a free-viewing system through a 2 mm artificial pupil. For the steady-state condition for all age groups, the functions were similar, but for the transient condition, the slope for the older observers was significantly less steep than that for the younger observers. These findings are consistent with an hypothesis of a selective loss of transient (Y) channels in the aging visual system.

No abstract

We wished to identify the experimental conditions that might yield a steeper brightness function than had been previously reported by other investigators for briefly presented flashes. White circular stimuli of 2° or 4° and 10, 30, 100 or 1000 ms were flashed in the center of four red fixation lights. Eighty-four subjects (17-26 years) were individually tested and introduced to magnitude estimation by scaling the lengths of line stimuli, after which they were dark adapted. Then each subject made brightness judgments of the stimuli which ranged in luminance from 0.216 to 216.2 cd/m2 in 0.3 log unit steps. No modulus was used. When presented alone, flashes of 10 or 30 ms yielded slopes similar to those obtained with 1000-ms stimuli. However, when stimulus durations of 10, 100, and 1000 ms were randomly presented, a significantly steeper slope resulted for the 10-ms flashes. The steeper brightness functions found for brief flashes in this and previous experiments may be contexually based, dependent on the presence of longer stimuli.

There is evidence from the psychophysical literature which suggests that low spatial frequency-high temporal frequency visual input is distinctly impaired in older observers. We are investigating these changes by measuring evoked potential amplitudes elicited by gratings of 0.6 and 6 cycles/deg flickered at 15 and 7.5 Hz, respectively, presented at a variety of contrasts. Three groups of subjects (young, middle-aged, and older) were composed of ten males each. The slope of the function relating VEP amplitude to stimulus contrast provides an index of visual system gain at low grating contrasts and serves as the dependent measure of the study. The psychophysical method of magnitude estimation is being employed as well to determine if age related changes in electrophysiological measures of amplitude are in agreement with changes in perceived contrast.