Apparently the former:
Perhaps one of the most important (and consistent) findings in E/I research is that extroverts are overall happier than introverts, and this increased happiness lasts for decades. Scientists have struggled to pinpoint the cause of extroverts’ happiness, though they are certainly not without ideas.
Researchers have proposed that extroverts may feel greater happiness than introverts because they are more sensitive to rewarding social situations. On the other hand, others have suggested that extroverts are happier because they engage in more social activities. Some scientists think that extroverts’ perpetual happiness stems from their greater mood regulation abilities. Or maybe they’re happy because they hold on tightly to all of those good memories.
At the same time, however, scientists have questioned whether extroverts really are happier, or if they’re just more declarative with their feelings. There’s also the issue of how, exactly, you define and measure “happiness.” Whatever the case, extroverts and introverts likely benefit from different happiness increasing strategies, given the inherent differences in the personality types.
Previous Dish on introverts and extroverts here. Rauch-related introversion here and here.
The Dish 