Individual differences in autonomic nervous system baselines often persist from birth, influencing how naturally relaxed or stressed a person or animal tends to be.

“And humans also, are within a range. I think anyone who's had children will tell you he or she has been like this since birth. Calm, easygoing, or like really easily stressed.”

Brain regions governing innate behaviors like aggression and mating are closely intermingled to allow the brain to prioritize competing behavioral priorities.

“They all seem to be closely intermingled with each other, maybe because crosstalk between them is very important to help the animal's brain decide what behavior to prioritize and what behavior to shut down at any given moment.”