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Steven Pinker -- How the Mind Works - Hampshire High Italian ...

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514 J HOW THE MIND WORKSconsequences are by no means minor. In a classic experiment, <strong>the</strong> socialpsychologist Muzafer Sherif carefully selected a group of well-adjusted,middle-class American boys for a summer camp, and randomly divided<strong>the</strong>m into two groups which <strong>the</strong>n competed in sports and skits. Withindays <strong>the</strong> groups were brutalizing and raiding each o<strong>the</strong>r with sticks, bats,and rocks in socks, forcing <strong>the</strong> experimenters to intervene for <strong>the</strong> boys'safety.The enigma of war is why people volunteer for an activity that has anexcellent chance of getting <strong>the</strong>m killed. <strong>How</strong> could a desire to play Russianroulette have evolved? Tooby and Cosmides explain it by <strong>the</strong> fact thatnatural selection favors traits that increase fitness on average. Every genecontributing to a trait is embodied in many individuals in many generations,so if one individual with <strong>the</strong> gene dies childless, <strong>the</strong> success ofmany o<strong>the</strong>rs with <strong>the</strong> gene can make up for it. Imagine a game of Russianroulette where if you don't get killed you have one more offspring. Agene for joining in <strong>the</strong> game could be selected, because five-sixths of <strong>the</strong>time it would leave an extra copy in <strong>the</strong> gene pool and one-sixth of <strong>the</strong>time it would leave none. On average, that yields .83 more copies thanstaying out of <strong>the</strong> game. Joining a coalition of five o<strong>the</strong>r men that is certainto capture five women but suffer one fatality is in effect <strong>the</strong> samechoice. The key idea is that <strong>the</strong> coalition acting toge<strong>the</strong>r can gain a benefitthat its members acting alone cannot, and that spoils are distributedaccording to <strong>the</strong> risks undertaken. (There are several complications, but<strong>the</strong>y do not change <strong>the</strong> point.)In fact, if <strong>the</strong> spoils are certain and divided up fairly, <strong>the</strong> level ofdanger doesn't matter. Say your coalition has eleven members and canambush an enemy coalition of five, taking <strong>the</strong>ir women. If one memberof your coalition is likely to be killed, you have a ten-in-eleven chanceof surviving, which would entitle you to a one-in-two chance (five captivewomen, ten men) of gaining a wife, an expected gain of .45 wives(averaged over many situations with <strong>the</strong>se payoffs). If two memberswill be killed, you have a smaller chance of surviving (nine in eleven),but if you do survive you have a larger chance of gaining a wife, sinceyour dead allies won't be taking <strong>the</strong>irs. The average gain (9/11 x 5/9) is<strong>the</strong> same, .45 wives. Even if six members are likely to be killed, so thatyour survival odds fall to less than even (five in eleven), <strong>the</strong> spoils aredivided fewer ways (five women among five victors), so if you $urviveyou are guaranteed a wife, for an expected gain, once again, of .45wives.

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