This hour, we question what decides the trajectory of our lives -- individual force of will, or fate?

If destiny isn't written in the stars, could it be written in our genes? Kids struggle to resist marshmallows, and their ability to holdout at age four turns out to predict how successful they're likely to be the rest of their lives. And an unexpected find in a convent archive uncovers early warning signs for dementia in the writings of 18-year-olds.

Correction: An earlier version of this piece incorrectly stated that the kids who performed better on the marshmallow test had higher GPAs in high school and went to better colleges. Those elements were not a part of Mischel’s original study. The audio has been adjusted to reflect this fact.