A new study sheds new light on these big questions, illuminating a general principle of neural processing in a mysterious region of the midbrain that is the very origin of our central serotonin (5-HT) system, a key part of the nervous system involved in a remarkable range of cognitive and behavioral functions.

Our lives are filled with binary decisions – choices between one of two alternatives. But what's really happening inside our brains when we engage in this kind of decision making?