Donald W. Kline

Age differences in target identification as a function of retinal location and noise level: Examination of the useful field of view.

Foveal and peripheral target detection were compared in young adults (M age = 22 years) and older adults (M age = 66 years) who were optically corrected for the viewing distance. In a two-alternative, forced-choice task, target letters were presented at 0 degree to 10.5 degrees from fixation. Targets were presented alone, flanked on each side by one noise element (i.e., nontarget letter), or embedded in a horizontal row of 19 noise elements. An Age X Noise Level X Location interaction was obtained, wherein age differences were largest for peripheral targets presented in noise. Slope analyses of latency data showed that the performance of young adults in the high-noise condition was most similar to that of older adults in the low-noise condition. At the functional level, results indicated that aging is associated with a restricted useful field of view. In addition, the data suggest that age differences in search can be described by a model in which older adults take smaller perceptual samples from the visual scene and scan these samples more slowly than do the young adults.

Ocular fixation control as a function of age and exposure duration.

In previous work we reported that fixation stability did not deteriorate in older adults over relatively long viewing durations. In the present study we reanalyzed the data to examine potential aging effects on fixational control for viewing durations typically used in psychological experimentation. Monocular eye movements were recorded in 12 older and 12 younger observers using a dual Purkinje image technique, while observers fixated a stationary target. The two-dimensional scatter of eye positions was measured during nine viewing durations ranging from 100 ms to 12.8 s. Fixational control of the two groups was comparable at all of the viewing durations. Both younger and older observers were able to maintain fixation within an area several times smaller than the size of the fovea. Implications for aging studies that use briefly presented visual stimuli are discussed.

The Estimation of Short Time Intervals as a Function of Age and Metronome Pacing

The accuracy of estimation of short time intervals was studied in old institutionalized and young college male and female participants as a function of three levels of audible background metronome rate (0, 40 and 90 beats/min). The main effects of metronome and interval length, as well as the age by metronome rate interaction, were significant. Unlike the young participants, the time judgments of the older participants were significantly and systematically determined by metronome rate. These results are consistent with the notion of increased field-dependence among older persons and suggest that their greater social conformity and their inability to ignore irrelevant stimuli might also be explicable in the same theoretical terms.

Processing Sense Information

If a person responds to a stimulus and then must respond to a second stimulus shortly afterward, the second response is often different from the first one, even if the two stimuli are identical. One explanation of this is that the first stimulus, in its neural representation, has not been “cleared through the nervous system” before a response must be made to the second stimulus. Since neural transmission of the first stimulus is not complete, the person is not optimally ready to process the second stimulus. The trace of the first stimulus persists, so to speak, leaving the responder either relatively refractory to subsequent stimulation or responsive but in a different way.

Stimulus persistence in CFF: Overarousal or underactivation?

The physiological basis of hypothesized adult age increases in the persistence of stimuli was studied in 16 young (X age 19.1 years) and 16 old (X age 70.1 years) male and female subjects. Changes in CFF threshold and skin conductance were measured as a function of loud white noise activation and artificial pupil. CFF was significantly lower in the old group and with artificial pupil in both age groups. Significant effects were also found for activation x sex and activation x age x sex. Skin conductance change was significant for activation, activation x sex, artificial pupil x age, artificial pupil x order and artificial pupil x order x activation. The results were interpreted as supporting an overarousal basis of an age increase in stimulus persistence.

Differences in inconspicuous word identification as a function of age and reversible-figure training

Inconspicuous word identification was studied in 48 young (X age 19.3 years), middle-aged (X age 44.5 years) and old (X age 69.5 years) male and female subjects. Although this task appeared to be an easy one for the young subjects, it was strikingly difficult for the middle-aged and elderly subjects. Reversible-figure training apparently led to a small but significant overall improvement in inconspicuous word identification but did not at all diminish the age differences in such performance. The interactions of sex by reversible-figure training and age by first set-second set of words were also significant. Further research will be needed to fully examine the remediability of age-related perceptual skill deficits.

Age and the identification of inconspicuous words

The purpose of these experiments was to examine systematically the basis for the profound inability of healthy, well-educated older subjects in earlier research to identify inconspicuous words. Two experiments were carried out in which inconspicuous words were formed of regular block letters composed in a black-on-white (Experiment 1) or a white-on-black format (Experiment 2). In both experiments the performance of the older persons was nonsignificantly below that of the younger subjects (an effect which reached significance when considered across the two experiments together). No effects were observed for contrast relationship or for a remediation of age deficits in inconspicuous word identification through interposed reversible figure training. The results suggest strongly that, for older persons, inconspicuous word identification is highly dependent upon the specific structural composition of the stimuli and is consequently explicable in terms of the already well-documented changes in perceptual function with age.