Sapolsky is a neuroscientist and field biologist who studies, among other things, the effects of stress on the brain, and its relation to depression, brain aging, and PTSD. He is also interested in how parasites manipulate the behavior of their hosts. He's looking in particular at toxoplasmosis, a disease caused by a parasite that causes rats to lose their fear of cats. Humans can become infected with the parasite, called Toxoplasma gondii. Sapolsky will report on how it might affect human behavior.