becca peixotto and jamie shreeve. thank you so much. >> thank you. >> ifill: it is amazing.rogram, "dawn of humanity," is streaming right now on www.pbs.org and will air next week on nova. >> ifill: you probably heard quite a bit during the last 24 hours about the latest cool new products from apple-- ipads and iphones that in some circles quickly become the latest must- have gadget. but what exactly makes a product "cool"? economics correspondent paul solman-- a pretty cool guy himself-- has been exploring that. here's what he found: part of our weekly series, "making sense," which airs every thursday on the newshour. >> reporter: an m.r.i. machine at the california institute of technology, where scientists are helping pioneer the study of neuroeconomics, how the brain makes economic decisions. the key brain structure that distinguishes us from fellow primates: the medial prefrontal cortex. >> it's a part of our brain that's tracking our social status or our perceived social status. >> reporter: in 2005, steve quartz and his cal tech colleagues were surprised to find that t