We know the beat of our heart varies over time, increasing with exertion and slowing with rest or meditation. But, stable as those variations may appear, they vary even within those intervals. Dr.

The effect of variability on learning is recognized in many fields: learning is harder when input is variable, but variability leads to better generalization of the knowledge we learned. In this ...

image: New research finds there is significant variation in the anatomy of the human digestive system, with pronounced differences possible between healthy individuals. The finding has implications ...