A recent study published in the journal Frontiers in Human Neuroscience focused on the neurotransmitter dopamine – —the “pleasure chemical” – in the extroverted brain, finding that the reason extroverts seem to experience stronger positive emotions may be all about how their brains process the memory of rewards.
Depue R.A. and Fu Y. Front. On the nature of extraversion: variation in conditioned contextual activation of dopamine-facilitated affective, cognitive, and motor processes. Hum. Neurosci. 13 June 2013