1.  The results of Experiment 2 replicated those of Experiment 1. Error rates were comparable for younger adults (2.4%) and older adults (2.1%).  Again, the display size effect varied between age groups (see Figure 4). RT slopes were significantly steeper for older adults (M = 123 ms/item) than for younger adults (M = 72 ms/item).  Distractor effects again diminished with increasing display size (see Figure 5). RTs in the compatible and incompatible conditions were significantly higher than RTs in the neutral condition at display sizes 2 and 4 but not at display size 6. RTs in the incompatible condition were significantly slower than those in the compatible condition only at display size 4.  Distractor effects did not vary as a function of age.  Error rates were comparable for younger adults (5.3%) and older adults (6.4%).  As depicted in Figure 2, search rates (display size effects) varied as a function of age group. RT slopes were significantly steeper for older adults (M = 60 ms/item) than for younger adults (M = 48 ms/item).  As depicted in Figure 3, there was an interaction of perceptual load and selective attention effects. The distractor effects diminished with increasing display size. RTs in both the compatible and incompatible conditions were significantly higher than RTs in the neutral condition, but only at display sizes 2 and 4, not at display size 6. RTs in the incompatible and compatible conditions did not differ significantly.  Contrary to prediction, distractor effects did not vary as a function of age. Maylor and Lavie (1998) reported that age differences in visual search are influenced by the interaction between perceptual load and selective attention. The disruption of visual search associated with response-incompatible distractors (presented outside of the search display) decreased as the number of items in the display (perceptual load) increased. This result was consistent with Lavie’s (1995) proposal that selection occurs only when capacity limitations are exceeded. Distraction effects were more pronounced for older adults than for younger adults at lower levels of perceptual load, but diminished more rapidly for older adults with increasing load. Maylor and Lavie characterized their findings in terms of (a) an age-related decline in inhibitory control, which limited the efficiency of selective attention at lower loads, and (b) an age-related reduction in processing capacity, which led to an improvement in selectivity with relatively smaller increases in load. We conducted two visual search experiments to explore the Maylor and Lavie (1998) findings further. We included both response-compatible and incompatible distractors to determine whether the distraction was due entirely to response selection. We also placed the distractors inside the display, to determine whether distraction required the presence of a single item outside the display configuration. Aging and Visual Search: Interaction of Perceptual Load and Selective Attention David J. Madden and Linda K. Langley Center for the Study of Aging and Human Development, and Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710 INTRODUCTION EXPERIMENT 1 Method 2 Display Size Effects for Experiment 1 4 Display Size Effects for Experiment 2 5 Distractor Effects for Experiment 2  Perceptual load and selective attention interact: The disruption of performance from irrelevant items decreases as a function of increasing display size. CONCLUSIONS  The distraction from irrelevant items occurs prior to response selection: The degree of disruption is comparable for response-compatible and incompatible items.  Under these viewing conditions, the efficiency of selective attention is not compromised substantially by aging. Acknowledgements This work was supported by National Institute on Aging grant R37 AG02163. Participants  32 younger adults (mean age 20 yrs, range 18-29 yrs) and 32 older adults (mean age 68 yrs, range 60-81 yrs). Stimuli and Procedure  The task was a two-choice version of visual search in which one of four target letters (H, C, S, or K) was present in the circular display on each trial.  Participants pressed one response key if the letters H or C were present and the other response key if the letters S or K were present.  Each display also contained two distractor letters and either one, three, or five nontarget letters.  The two distractor letters were positioned at 3 and 9 o’clock within the circle. Participants were instructed to ignore these distractors. Thus, the number of relevant display items was 2, 4, or 6 (see Figure 1).  The identity of the distractor was determined by the trial condition (response-compatible, incompatible, and neutral). For example, if the identity of the target letter was C, the distractors’ identity was H in the compatible condition, S or K in the incompatible condition, and R in the neutral condition.  Following presentation of a warning signal (asterisk) for 500 ms, the display appeared for 250 ms for younger adults and 750 ms for older adults. Display offset was followed by a blank screen. For both younger and older adults, 2500 ms from the onset of the display was allowed for the response. EXPERIMENT 2 Method Participants  24 younger adults (mean age 20 yrs, range 18-24 yrs) and 24 older adults (mean age 70 yrs, range 60-81 yrs). Stimuli and Procedure  The task and procedures were the same as those used in Experiment 1, except the display remained on the screen until a response was made or 10 sec had elapsed. References Lavie, N. (1995). Perceptual load as a necessary condition for selective attention. Journal of Experimental Psychology: Human Perception and Performance, 21, 451-468. Maylor, E. A., & Lavie, N. (1998). The influence of perceptual load on age differences in selective attention. Psychology and Aging, 13, 563-573. Experiment 1 Results 3 Distractor Effects for Experiment 1 Experiment 2 Results 1 Sample Displays for Each Trial Condition and Display Size (the target is the letter C in each display) 6 4 Display Size: 2 Compatible Incompatible Neutral H F C HR F C R S F C S L H T C H D S T S C D L S C S L Q XB T R T R C D L R C R L Q X B T H C H Q XB T L -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200 246246 Display Size Difference Score (ms) Incompat. - Neutral Compat. - Neutral Younger AdultsOlder Adults -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200 246246 Display Size Difference Score (ms) Incompat. - Neutral Compat. - Neutral Younger AdultsOlder Adults 1850 0 750 850 950 1050 1150 1250 1350 1450 1550 1650 1750 1850 246246 Display Size Reaction Time (ms) Incompatible Compatible Neutral Younger AdultsOlder Adults 0 750 850 950 1050 1150 1250 1350 1450 1550 1650 1750 246246 Display Size Reaction Time (ms) Incompatible Compatible Neutral Younger AdultsOlder Adults