Johari/Nohari
"Tell someone you love them today, because life is short; shout it at them in German, because life is also terrifying."
Fruit, the fluffy kitty.
S+N+D higher = more lively = extrovert (not necessarily extrotim)
Calculate your rates - they may be high, moderate, or low.
Add 1 for each high rate, and subtract 1 for each low rate.
If your "liveliness score" is positive, you're more likely an extrovert. If it's negative, you're more likely an introvert. If zero, then... one of both are possible.
If you want to know the role of such neurotransmitters, you can search on Wikipedia or such.