Researchers have found that people who are sleep-deprived have difficulty reading the facial expressions of other people, particularly when the expressions are more subtle. [snip]
In neuroimaging studies, scientists have discovered that sleep deprivation can amplify activity in the amygdala, a part of the brain that plays a key role in processing emotions, and weaken activity of the prefrontal cortex, which is critical for regulating emotions.
1) the more research that is done on sleep, the more important we're finding sleep to be;
2) don't play poker when you're tired.