These findings may come as no shock to you if you're a parent, the study results are good reminds that things will get better with time. Impatience, after all, is thought by some to be the same as impulsivity, a more notorious disease-associated term, and criteria for ADD / ADHD.
The top figure shows that older children (brown) are better at delaying gratification than younger (blue), but ability to wait is also affected by the amount of the increase in reward.
Boys are less patient than girls, but this too improves with age.
In the figure below, we've excerpted two figures that show distinct patterns of activation depending on the reward is immediate (today) or delayed (1 month away). Some sites (like the ventral striatum) are more activated by immediate rewards, while others (like the right parietal area - and other frontal areas - see paper) appear content either way.
Boys and Younger Children Less Patient pdf
Immediate and Delay Gratification & fMRI pdf