Age differences in what is viewed and remembered in complex conjunction search

Abstract

Older and younger adults searched arrays of 12 unique real-world photographs for a specified object (e.g., a yellow drill) among distractors (e.g., yellow telephone, red drill, and green door). Eye-tracking data from 24 of 48 participants in each age group showed generally similar search patterns for the younger and older adults but there were some interesting differences. Older adults processed all the items in the arrays more slowly than the younger adults (e.g., they had longer fixation durations, gaze durations, and total times), but this difference was exaggerated for target items. We also found that older and younger adults differed in the sequence in which objects were searched, with younger adults fixating the target objects earlier in the trial than older adults. Despite the relatively longer fixation times on the targets (in comparison to the distractors) for older adults, a surprise visual recognition test revealed a sizeable age deficit for target memory but, importantly, no age differences for distractor memory.

Keywords:

• Visual Search
• Ageing
• Eye Movements
• Visual Memory

Acknowledgments

This research was supported by National Institute of Aging Grant AGO 4306 to Lynn Hasher and Rose T. Zacks, National Science Foundation Grant BCS 0094433 to John M. Henderson, and Army Research Office Grant DAAD 19-00-1-0519 to John M. Henderson. This research derives from a doctoral dissertation submitted by Carrick C. Williams to Michigan State University. Aspects of the data were reported at the Third Annual Meeting of the Vision Science Society, Sarasota, FL, April 2003, and the 44th Annual Meeting of the Psychonomic Society, Vancouver, BC, Canada, November 2003.

The younger adult data for the eye-tracking version of this experiment were previously published in Williams, Henderson, and Zacks (2005). The previous study explored how viewing behaviour influenced visual memory. The current study is focused on age-related differences in the search pattern. To accomplish this goal, we report a different set of eye-tracking analyses from those previously reported for the younger adults and compare the eye movement patterns to a group of older adults. Additionally, for the memory data reported here, we combine the data from Williams et al. with another experiment and report the combined data and the age comparisons. We thank the dissertation committee members of Tom Carr and Zach Hambrick for their helpful discussion and comments on the dissertation. We also thank Camilla Williams for her comments on previous drafts of this manuscript.

Notes

¹ A total of 4 older adults in the eye-tracking portion of the study did not provide any correct responses in the three-target condition and thus were excluded from the search time analysis.

² It is important to note that within an object type, each ordinal fixation represents an independent observation. In other words, because the displays are randomly arranged, whether one looks at a target on, for example, Fixation 4, does not necessarily constrain one to look at a target on Fixation 5. However, across object types (target, colour distractor, category distractor, and unrelated distractor), the observations are not independent (e.g., if one is looking at the target on Fixation 4, one cannot look at a colour distractor on Fixation 4). To account for this fact, we only report the three-way interaction term of the overall analysis, which examines the patterns of the observations for the two age groups. We then analyse the data for each object type separately to eliminate any concern of nonindependence.

³ When all targets (those seen on one or both trials) are considered.

⁴ One younger adult had perfect memory for the target objects seen in the total time analysis. This participant was removed from all total time analyses. The results do not change if this participant is included with a slope of 0 and an intercept of 1.