Figure 2: Monetary Reward Effects on Reward Rate by Age Group.

In Figure 2a, reward rate is plotted against age group (OA=older adults, YA=younger adults). The dashed line represents the expected reward rate of 30%, assuming subjects did not improve their performance between baseline and incentive blocks. The solid lines represent 95% confidence intervals calculated by a binomial test [CI_lower=.25, CI_higher= .35]. Each dot represents a single subject’s average reward rate. Figure 2b illustrates that while older adults are generally slower than younger adults, motivational incentives are associated with a significant reduction in response times (ms) between baseline and incentive blocks for both older and younger adults. Figure 2c shows accuracy between baseline and incentive blocks. Here, older adults maintained their accuracy between baseline and incentive blocks, whereas younger adults showed a significant drop in accuracy (i.e., they shifted down the speed-accuracy curve to increase reward rate). All error bars in all plots indicate standard error of the mean.