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

448 | HOW THE MIND WORKSmarriage, and other outcomes that are good for the parent (and hencethe child's unborn siblings) are in fact good for the child. As in all arenasof conflict, parents may resort to deception and, since children are nofools, self-deception. So even if children acquiesce to a parent's rewards,punishments, examples, and exhortations for the time being becausethey are smaller and have no choice, they should not, according to thetheory, allow their personalities to be shaped by these tactics.Trivers went out on a limb with that prediction. The idea that parentsshape their children is so ingrained that most people don't even realize itis a testable hypothesis and not a self-evident truth. The hypothesis hasnow been tested, and the outcome is one of the most surprising in thehistory of psychology.Personalities differ in at least five major ways: whether a person issociable or retiring (extroversion-introversion), whether a person worriesconstantly or is calm and self-satisfied (neuroticism-stability), whetherthe person is courteous and trusting or rude and suspicious (agreeableness-antagonism),whether a person is careful or careless (conscientiousness-undirectedness),and whether a person is daring or conforming(openness-nonopenness). Where do these traits come from? If they aregenetic, identical twins should share them, even if they were separatedat birth, and biological siblings should share them more than adoptivesiblings do. If they are a product of socialization by parents, adoptive siblingsshould share them, and twins and biological siblings should sharethem more when they grow up in the same home than when they growup in different homes. Dozens of studies have tested these kinds of predictionson thousands of people in many countries. The studies havelooked not only at these personality traits but at actual outcomes in lifesuch as divorce and alcoholism. The results are clear and replicable, andthey contain two shockers.One result has become well known. Much of the variation in personality—aboutfifty percent—has genetic causes. Identical twins separatedat birth are alike; biological siblings raised together are more alike thanadopted siblings. That means that the other fifty percent must comefrom the parents and the home, right? Wrong! Being brought up in onehome versus another accounts, at most, forgive percent of the differencesamong people in personality. Identical twins separated at birth are notonly similar; they are virtually as similar as identical twins raisedtogether. Adoptive siblings in the same home are not just different; theyare about as different as two children plucked from the population