and have them watch a horror movie and then had them describe there feelings for their wives. the brain scans or the same in both circumstances. it's just sheer terror. i know what that is like. it's not a natural thing. yet emotions really are the center of how we perceive the world, about you the world. they're the center of our brain organizes itself. >> you can watch this and other programs online at book tv -- booktv.org. >> what are you reading this summer? book tv wants to know. ♪ tell us what you're reading this summer. send us a tweet at book tv. >> next on book tv alison ...