Suppose you’re at a vending machine and you insert a dollar bill to get a candy bar. But instead of one candy, as you would expect, you receive two candies. You think: “This is a pleasant surprise, ...

A new study on laboratory rats has found that the brain’s ability to learn from rewards is enhanced by the hormone estrogen. The work shows that naturally cycling estrogen levels alter the brain’s ...

Pupil dilation provides a physiological readout of information gain during the brain's internal process of belief updating in the context of associative learning.