Joan M. McDowd

Aging, selective attention, and inhibitory processes: a psychophysiological approach.

The present study investigated the efficiency with which younger and older adults allocate attention to relevant and irrelevant stimuli. The model of attention guiding this research links the orienting response with the allocation of attention and habituation with the inhibition of the allocation of attention. We adapted a paradigm developed by Iacono and Lykken (1983) in which subjects are instructed unambiguously either to attend to or to ignore a series of innocuous tones, and the skin conductance orienting response elicited by each tone is measured. Results revealed that young subjects instructed to ignore the tones habituated more quickly than did those instructed to attend to the tones. However, older adults exhibited nondifferential orienting across the 2 instruction conditions. These results suggest an age-related deficit in the ability to inhibit attention to irrelevant stimuli.

Age differences and similarities in patterns of cerebral hemispheric asymmetry

Younger (M age = 20.4 years) and older (M age = 70.7 years) adults participated in 3 visual half-field experiments. These were designed to examine specific aspects of hemispheric asymmetry: (a) hemispheric dominance for phonetic-linguistic processing (as measured by identification of non-word trigrams), (b) hemispheric differences in trigram processing strategy, (c) characteristic perceptual biases thought to reflect hemispheric arousal asymmetries, and (d) hemispheric dominance for processing emotions shown on faces. Patterns of left-right asymmetries were comparable for older and younger participants, and intercorrelations among the various measures of asymmetry were similar for both groups. In view of the present results, it seems unlikely that changes in hemispheric asymmetry contribute significantly to age-related changes in cognitive functioning.

Facilitating word-fragment completion with hidden primes

Two experiments tested the effectiveness of priming on word-fragment completion when the priming operation consisted of the presentation of target words in the instructions for the fragment-completion task. Reliable priming effects were obtained in both experiments. The second experiment also examined the influence of case change of printed materials on the extent of priming effects. No simple outcome occurred, as the effects of case change or constancy were not symmetrical with respect to upper- and lowercase.

Ineffectiveness of visual distinctiveness in enhancing immediate recall

Glenberg (1984) and others have theorized that greater recency effects are obtained with auditory as opposed to visual presentation because of greater temporal distinctiveness of items in auditory sequences. We tested a number of ways of enhancing visual distinctiveness, including the use of color, spatial location, and minimized visual interference. None of the seven experiments provided any evidence of improved recall from enhanced visual distinctiveness. In particular, no increase in recency effects was obtained with increased distinctiveness. Additional analyses of pairwise dependency in recall across serial positions also failed to show any evidence of the near-independence of recall of the terminal item that characterizes recall of auditory sequences. Visual-perceptual distinctiveness does not get mapped in any simple way onto memorial distinctiveness in an immediate-serial-recall task.

Effects of Age and Practice on Attention and Stages of Information Processing Using CRT with Fixed and Variable Foreperiods

The results of previous investigations have found conflicting results on the locus of age-related slowing of reaction time using Additive Factors Method (Sternberg, 1969). This experiment was conducted to examine the differential effects of Additive Factors Method task manipulations using both fixed and variable foreperiod conditions with practice preceding a second day replication to quantify the interaction of these effects with skill. The results show that (1) practice is a major confounding for research involving RT tasks, (2) the locus of age effects may lie in the later response selection stage of processing, and (3) the effects of aging, practice and intra-task factors depend on the response-stimulus interval characterizing the RT task. This research has implications for improving research methodologies and understanding the nature of age-related slowing in central nervous system functions.

Effects of Age, Gender, Activation, Stimulus Degradation and Practice on Attention and Visual Choice Reaction Time

This paper presents research conducted by the authors and others investigating the interaction of a variety of variables which are presumed to affect reaction time in hopes of obtaining much needed information on factors influencing age effects on attention and information processing. Reported is progress to date on an experiment which shows that the effects of age on central nervous system speed, as measured by visual choice reaction time, depends on many factors, including the gender, neural activation level, and skill of the subject as well as the stimulus quality and type of reaction task employed.