Hockenbury Discovering Psychology 5th txtbk

308 CHAPTER 7 Thinking, Language, and IntelligenceFigure 7.9 The Two Pots AnalogyBecause the two environments are verydifferent, no conclusions can be drawnabout possible overall genetic differencesbetween the plants in pot A and theplants in pot B.Corn plantsIndividual differences inheight within the groupare due to geneticsbecause environment isthe samePot ARich soil, many nutrientsPot BPoor soil, few nutrientsDifference in average heightbetween groups is due toenvironmentpot A. In other words, the average differences within a group of plants tell us nothingabout whether an individual member of that group is likely to be tall or short.The same point can be extended to the issue of average IQ differences betweenracial groups. Unless the environmental conditions of two racial groups are virtuallyidentical, it is impossible to estimate the overall genetic differences between the twogroups. Even if intelligence were primarily determined by heredity, which is not thecase, IQ differences between groups could still be due entirely to the environment.Other evidence for the importance of the environment in determining IQ scoresderives from the improvement in average IQ scores that has occurred in several culturesand countries during the past few generations (Flynn, 2007a, 2007b; Neisser& others, 1996).In a survey of intelligence test scores around the world, 14 nations were foundto have shown significant gains in average IQ scores in just one generation (Flynn,1994, 1999). The average IQ score in the United States has also steadily increasedover the past century (Flynn, 2007a, 2007b). Such changes in a population can beaccounted for only by environmental changes, because the amount of time involvedis far too short for genetically influenced changes to have occurred.We need to appreciate that all humanbehavior is based on biology and,hence, will involve some degree ofgenetic influence. But, equally, allsocial behavior is bound to be affectedby social context and, hence, willinvolve an important environmentalinfluence.MICHAEL RUTTER (1997)Cross-Cultural Studies of Group Discriminationand IQ DifferencesThe effect of social discrimination on intelligence test scores has been shown innumerous cross-cultural studies (see Ogbu, 1986, 2008). In many different societies,average IQ is lower for members of a discriminated-against minority group,even when that group is not racially different from the dominant group. The Cultureand Human Behavior box on page 310 explains how belonging to a stigmatizedgroup can affect performance on tests of many different abilities.