This study used feature-integration theory as a means of determining the point in processing at which selective attention deficits originate. The theory posits an initial stage of processing in which features are registered in parallel and then a serial process in which features are conjoined to form complex stimuli. Performance of young and older adults on feature versus conjunction search is compared. Analyses of reaction times and error rates suggest that elderly adults in addition to young adults, can capitalize on the early parallel processing stage of visual information processing, and that age decrements in visual search arise as a result of the later, serial stage of processing. Analyses of a third, unconfounded, conjunction search condition reveal qualitatively similar modes of conjunction search in young and older adults. The contribution of age-related data limitations is found to be secondary to the contribution of age decrements in selective attention.
Three hypotheses tested relationships between cardiac responses mediated via the vagus and sustained attention in a population of normal school-age children. These hypotheses addressed the theoretical relationships among resting cardiac vagal tone (using the Porges estimate of respiratory sinus arrhythmia, V), performance measures of sustained attention, and cardiac reactivity during sustained attention. Thirty-two fourth and fifth grade children performed a continuous performance task while their electrocardiograms were monitored. Children with higher resting levels of V performed better on the first 3-min block of the continuous performance task. Additionally, levels of V were significantly reduced across the blocks of the 9-min task for all children. No relationships were found between resting levels of V and change in either V or heart period during task performance. These findings support two of the three hypotheses proposed by Porges regarding individual differences in cardiac vagal tone and sustained attention.
Two experiments were conducted to assess age differences in the selectivity of visual information processing. Selectivity was measured by the amount of interference caused by nontarget letters when subjects detected a target letter in a visual display. In both experiments, young and elderly groups participated in search and nonsearch conditions; in the search condition targets appeared anywhere in the display, whereas in the nonsearch condition targets were confined to the center position of the display. In the first experiment, subjects were assigned to either condition for two sessions of testing, and in the second experiment each subject participated in both conditions. In both experiments nontargets produced larger interference effects for old compared to young adults in the search condition but not in the nonsearch condition. The obtained pattern of age effects could not be explained by age-related reductions in parafoveal acuity. The findings indicate that the magnitude of divided-attention deficit increases with age, whereas focused-attention deficits are unaffected by aging.
Previous research has indicated age-related declines in visual search and memory search performance. Recent nondevelopmental evidence suggests that after extensive practice with a consistent stimulus set, performance in search tasks becomes independent of information load. Eight volume (mean age 23.55 years) and eight elderly (mean age 74.92 years) females searched for either two or four target letters which appeared individually in displays of one, four, or nine letters using either an unchanging memory set (consistent mapping) or changing memory sets (varied mapping); subjects performed over six sessions. Under the varied mapping condition the traditional pattern of age-associated decrement in search was obtained, while in the consistent mapping condition adult age differences were attenuated. These findings supported the hypothesis that age-related decrements in visual search can be eliminated, or at least minimized, when various control processes such as selective attention are short-circulated by automatic information processing.
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