To some of us it sounds like sacrilege, but as a couple of my Inc.com colleagues have recently pointed out, coffee isn't all instant energy and delicious aroma. The pick-me-up beverage of choice for so many entrepreneurs also causes withdrawal, reduces rationality (thanks to increasing adrenaline in your body) and can be the culprit for those suffering insomnia, indigestion, or even dehydration. (But don't worry diehard fans, there is also plenty of research to lean on if you want to justify your coffee habit.)

As interesting as this to and fro on the pros and cons of coffee might be, in his new book Me, Myself, and Us: The Science of Personality and the Art of Well-Being psychologist Brian Little suggests that we may be missing an interesting and important wrinkle in the great coffee debate. It turns out, coffee might not be absolutely good or bad, but dependent not only on context (surely some ill-advised late night espresso already taught you that) but also personality type.

Introverts and extroverts handle caffeine differently.

Introverts, skip that pre-meeting Starbucks run

"After ingesting about two cups of coffee, extraverts carry out tasks more efficiently, whereas introverts perform less well. This deficit is magnified if the task they are engaging in is quantitative and if it is done under time pressure," Little writes. "For an introvert, an innocent couple cups of coffee before a meeting may prove challenging, particularly if the purpose of the meeting is a rapid-fire discussion of budget projections, data analysis, or similar quantitative concerns. In the same meeting, an extraverted colleague is likely to benefit from a caffeine kick."

Why this gulf in response to caffeine between introverts and extraverts? New York Magazine's Science of Us column emailed Little to get some more information. His conclusions, it turns out, are rooted in Hans Eysenck's theory of extraversion and research by William Revelle of Northwestern University.

This science states that "introverts and extraverts differ in the level of neocortical arousal in the brain--in other words, how alert or responsive you are to your environment," Little explains. "Introverts are over the optimal level--that is, more easily stimulated--and extraverts under the optimal level... This suggests that performance will be compromised for introverts if they are exposed to stimulating situations, or if they ingest a stimulant (such as caffeine), which pushes them even further away from the optimal level."

Is caffeine ever good for introverts?

That's slightly sad news for introvert coffee lovers, but don't worry, the news isn't all bad if you're a quieter type who loves your caffeine. You can still enjoy a cup here and there, Little adds. You just need to be strategic about your timing. "Later in the day would be better; at any rate, they should try not to have caffeine right before something like an important meeting," he concludes.

Published on: Oct 24, 2014