Influence of response selection and noise similarity on age differences in the redundancy gain.

We examined the impact of target redundancy for target-plus-noise (TPN) and target-only (TO) trials. Experiment 1 manipulated response selection load (two-choice vs go/no-go) and Experiment 2 (all two-choice) varied noise redundancy (single or cumulative noise letters) on a visual search, divided attention task in which target letters were presented in one, two, or three corners of a four-corner display. Half of the trials also included noise letters. For Experiment 1, there was a definite redundancy gain for TO trials. Furthermore, older adults, relative to young adults, evidenced an even larger redundancy gain for TO trials than for TPN trials, although response selection load did not interact with age. These results are consistent with the notion that older adults exhibit a processing resources decrement. For Experiment 2, older adults evidenced a relatively larger redundancy gain for TPN trials than for TO trials, and this was especially the case for TPN trials in which all nontarget locations were filled with noise letters. Experiment 2 results are consistent with the notion that older adults also exhibit a selective attention decrement.