Abstract
Previous investigations of adult age differences in visual search suggest that an age-related decline may exist in attentional processes dependent on the observer's knowledge of task-relevant features (top-down processing). The present experiments were conducted to examine age-related changes in top-down attentional guidance during a highly efficient form of search, singleton detection. In Experiment 1 reaction times to detect targets were lower when target features were constant (feature condition) than when target features were allowed to vary between trials (mixed condition), and this reaction time benefit was similar for younger and older adults. Experiments 2 and 3 investigated possible interactions between top-down and bottom-up (stimulus-driven) processes. Experiment 2 demonstrated that search times for both age groups could be improved when targets varied on an additional feature from distractors (double-feature condition) but only when top-down control was available (feature search). In Experiment 3, the availability of top-down guidance enabled both younger and older adults to override the distracting effects of a noninformative spatial location cue. These findings indicate that top-down attentional control mechanisms interact with bottom-up processes to guide search for targets, and that in the context of singleton detection these mechanisms of top-down control are preserved for older adults.
Acknowledgments
This research was supported by grants R37 AG02163 and T32 000029 from the National Institute on Aging. We are grateful to Susanne M. Harris, Sara Moore, Niko Harlan, and Leslie Crandell Dawes for technical assistance. Barbara Bucur and Julia Spaniol provided helpful comments on a draft of this article.
Notes
Now at the Department of Psychology, Washington and Lee University.
We refer to these conditions as feature, dimension, and mixed to characterize the different types of information available for attentional guidance. It is important to note that all three task conditions are a form of feature search, in which the target differs from the distractors on a single feature.
Colour was not relevant in this task. To maintain similarity to the size and orientation singletons in Experiment 1, all of the items in each display were the same colour, either red or green, and display colour was alternated randomly across trials within each trial block.
Details of these analyses are available from the corresponding author.
