Suchergebnisse

AbstractAll psychological and psychophysiological traits vary, often widely, about their stable set-point values, due to transitory environmental influences. Because it is this stable set-point that embodies the genetically determined component of the trait, twin and family data based on one-time trait measurements must underestimate true trait heritability. The means of multiple measurements, taken months or years apart, then correlated within pairs of monozygotic twins, would yield an accurate estimate of the broad heritability of the set-point value, but such data are rare and expensive. Given just two measurements sufficiently far apart, the cross-twin cross-time correlation (RCT), divided by the retest or within-twin cross-time correlation (RWT), provides a valid estimate of set-point heritability. This article examines data from young and middle-aged twins who were tested twice, 3 or more years apart, on heart rate and blood pressure, personality traits, self-rating items, occupational and recreational interests, as well as on Wechsler Intelligence Scales. In every case, the disattenuatedRCTrevealed substantially higher heritability than indicated by correlations based on single measurements.

This is the first of a series of three articles on IQ, heredity, & equality. Focus here is on A. Jensen's hypothesis (Educability and Group Differences, New York: Harper & Row, 1973) that the mean IQ short-fall for blacks is genetically caused. Consideration is given to the theoretical & logical structure of the argument that intergroup variations in average IQ are primarily influenced by heredity. Original data from heritability studies involving separated identical twins are untrustworthy, besides which, such statistics apply only to specific breeding & rearing populations, & they cannot be generalized to other populations. The heritability of a trait may be nothing more than a function of the extent to which salient features of the environments in which the observed population lives are themselves alike or unlike. Within-group variance cannot be generalized to account for between-group differences. Ss of twin studies involve much less group-environment conflict than is true for black people in largely white America. No plausible historical or anthropological account has been offered as to why ex-Africans in America should have disfavored genes for intelligence. The heritability of the intelligence-as-measured-by-IQ is irrelevant to questions of causation & prognosis; that kind of intelligence is a malleable trait. If inheritance is discounted as a major cause of between-group differentials in IQ, it is not difficult to find aspects of environment that can reasonably & clearly be expected to have had a striking differential impact on the IQ performances of the races in the US. Jensen's "genetic hypothesis" is not only illogically applied to interracial comparisons, it is unnecessary & misconceived for explaining the racial IQ gap. AA.

AT PRESENT, IT IS IMPOSSIBLE TO KNOW THE DEGREE OF GENETIC DETERMINATION OF INDIVIDUAL CHARACTERISTICS, IE, THEIR HERITABILITY. MAJOR PROBLEMS OF RELIABILITY ARE MANIFOLD. A CHILD WITH GENOTYPICALLY HIGH INTELLIGENCE MAY MAGNIFY HIS ADVANTAGE BY SHAPING HIS OWN ENVIRONMENT, WHICH THUS MAY BECOME MORE RESPONSIVE TO HIS NEEDS. A CHILD WITH GENOTYPICALLY LOW INTELLIGENCE, BEING AT A DISADVANTAGE, MAY NOT RESPOND TO HIS OWN ENVIRONMENT IN WAYS WHICH CAN AMPLIFY HIS EXPERIENCES. THIS RAISES A QUESTION AS TO THE JUSTICE OF ADULT RESPONSE TO CHILDREN WHICH ENCOURAGES SOME & DISCOURAGES OTHERS. NO MEANINGFUL ESTIMATE OF THE IMPORTANCE OF SUCH INDIRECT GENETIC EFFECTS CAN BE MADE. WHERE IQ IS CONCERNED, IQ'S HERITABILITY MAY BE CALCULATED EVEN THOUGH WE DO NOT KNOW WHAT IQ REALLY IS, OR WHAT VALUE IT HAS. HERITABILITY ESTIMATES ARE USEFUL ONLY IN THAT THEY RELATE TO POSSIBILITIES FOR CHANGE IN PRESENT CIRCUMSTANCES; THEY HAVE NO FUNCTION IN PREDICTING POTENTIAL CHANGES ARISING FROM NEW ENVIRONMENTAL SITUATIONS. WHERE DYSGENICS IS CONCERNED, GIVEN THE SUSPICION THAT IQ TESTS HAVE LIMITED VALUE IN JUDGING INTELLIGENCE, ANY EUGENIC PROGRAM SEEMS FRAUGHT WITH PROFOUND MORAL QUESTIONS. ARGUMENTS REGARDING SOCIAL STRATIFICATION & ITS INEVITABLE STRENGTHENING THROUGH GENETIC REINFORCEMENT ARE SOPHISTICATED BUT FALLACIOUS. WHILE SOME R DOES SEEM TO EXIST BETWEEN IQ & SOCIAL STANDING, THIS MIGHT BE DETERMINED BY A GREAT MANY NONGENETIC FACTORS RELATING TO THE ENVIRONMENT WHICH STATUS & MONEY IN OUR SOCIETY PROVIDE. SUCH IDEOLOGICAL & RACIST OVERTONES IN HERITABILITY DISCUSSIONS RAISE SERIOUS QUESTIONS OF SCIENTIFIC ETHICS; THE WIDE DISSEMINATION & POSSIBLE MISINTERPERTATIONS OF THEIR CONCLUSIONS ARE MAJOR PROBLEMS. SCIENTISTS DO HAVE A CERTAIN OBLIGATION TO CONSIDER THE MORAL IMPLICATIONS OF THEIR RESEARCH & THE POSSIBLE MISUSE OF RESULTS. STUDIES OF HERITABILITY OF IQ SHOULD CERTAINLY CONTINUE; STUDIES WHICH EMPLOY RACE AS THEIR MAJOR VARIABLE, HOWEVER, PARTICULARLY IN VIEW OF OUR TREMENDOUSLY IMPERFECT KNOWLEDGE OF THE VALUE OF IQ, SHOULD BE STOPPED. 1 FIGURE. C. LELAND.

AbstractWe examine the heritability of psychological resilience among US adults aged 25 to 74 years. Using monozygotic and same sex dizygotic twin pairs from the National Survey of Mid-Life Development in the United States (MIDUS) we show that positive affect is equally heritable among men (h2= .60) and women (h2= .59). We then estimate the heritability of positive affect after controlling for an exhaustive list of social and inter-personal stressors, and we operationalize the residual for positive affect as resilience. According to this specification, the heritability of resilience is higher among men (h2= .52) compared to women (h2= .38). We show that self-acceptance is one of the most important aspects of psychological functioning that accounts for the heritability of resilience among both men and women. However, compared to women, men appear to derive additional benefits from environmental mastery that may enable otherwise sex-neutral resilient tendencies to manifest.

A NEW LOOK AT THE CONCEPT OF 'INTELLIGENCE TESTS' IS REQUIRED, IN VIEW OF THE CONTROVERSIAL 'GENETIC INEQUALITY OF THE RACES' & 'STERILIZATION OF THE LOW IQ' THEORIES FOSTERED IN SOME PLACES TODAY. INTELLIGENCE IS MOST AMBIGUOUSLY DEFINED, YET POPULARLY SO, AS "WHAT IQ TESTS MEASURE." THIS LACK OF CLEAR DEFINITION FOR THE TERM IMPLIES A REAL LACK OF A THEORY OF INTELLIGENCE & AN ATTENDANT VALIDITY QUESTION IN REGARD TO WHAT IQ TESTS DO MEASURE. SOME R DOES EXIST BETWEEN THE IQ TEST SCORE & SUCCESS IN SCHOOL & SOCIETY, BUT ARE WE REALLY MEASURING INTELLIGENCE WITH IQ TESTS, OR IS IT FACTORS OF MOTIVATION, 'TEST-WISENESS', CULTURAL BACKGROUND, ETC? IQ TESTS ARE FOUNDED ON AN UNSTATED THEORY: THEY TEST KNOWLEDGE & DEVELOPED SKILLS ON THE ASSUMPTION THAT THOSE QUALITIES MEASURE INTELLIGENCE. THEY MAKE NO ALLOWANCES FOR THE DIFFERENTIAL IN SUBJECT'S ACCESS TO INFORMATION, OR FOR VARIABLES IN MOTIVATION, INTEREST, ETC. NO ACCOUNT IS TAKEN OF INDIVIDUAL'S VARYING CAPACITIES TO DEMONSTRATE KNOWLEDGE OF THE TYPE DEMANDED BY THE TEST, WHILE SUCH ASPECTS OF INTELLIGENCE AS CREATIVITY ARE IGNORED ENTIRELY. THE TESTS ASSUME THE EXISTENCE OF 'GENERAL INTELLIGENCE'--SOMETHING LIKE ABSTRACT REASONING ABILITY--DESPITE THE FACT THAT PSYCHOMETRICIANS THEMSELVES ARE DEEPLY DIVIDED AS TO THE EXISTENCE OF THIS ENTITY. 3 FIGURES. C. LELAND.

Attitudes towards foreign policy have typically been explained by ideological and demographic factors. We approach this study from a different perspective and ex amine the extent to which foreign policy preferences correspond to genetic variation. Using data from the Minnesota Twin Family Study, we show that a moderate share of individual differences in the degree to which one's foreign policy preferences are hawkish or dovish can be attributed to genetic variation. We also show, based on a bivariate twin model, that foreign policy preferences share a common genetic source of variation with political ideology. This result presents the possibility that ideology may be the causal pathway through which genes affect foreign policy preferences.

AbstractExperimental studies have suggested biological factors as a possible explanation for gender disparities in perception of pain. Recently, heritability of liability to neck pain (NP) has been found to be statistically significantly larger in women compared to men. However, no studies have been conducted to determine whether the sex differences in heritability of NP are due to sex-specific genetic factors. Data on lifetime prevalence of NP from a populationbased cross-sectional survey of 33,794 Danish twins were collected and age-stratified univariate biometrical modeling using sex-limitation models was performed based on 10,605 dizygotic (DZ) twins of opposite sex to estimate the qualitative sex differences. In a full sex-limitation model the genetic component in females were higher than in males, but the genetic and the shared environmental correlations were equal to what is normally assumed between same-sex DZ twins. A 'no-sex-effects' model showed the overall best model fit which confirms absence of sex-related gene interaction. The age-stratified sex-limitation models showed similar results. Thus, there is no evidence for a sex-specific genetic influence in the liability of heritability of NP.

"Genetics and Heritability Research on Political Decision Making" published on by Oxford University Press.

AbstractThe propensity to take risk underpins a wide variety of decision-making behavior, ranging from common ones such as asking for directions and trying out a new restaurant to more substantial economic decisions involving, for instance, one's investment or career. Despite the fundamental role of risk attitude in the economy, its genetic basis remains unknown. Using an experimental economics protocol combined with a classical twin strategy, we provide the first direct evidence of the heritability of economic risk attitude, at 57%. We do not find a significant role for shared environmental effects, a common observation in behavioral genetics that is contrary to commonly held views in economics. Our findings complement recent neuroeconomic studies in enhancing the understanding of the neurobiological basis of risk taking.

Since the invention of the intelligence test, there have been frequent claims that the existence of a substantial genetic component to IQ scores has important implications for education. From Terman to Herrnstein and Murray, the social scientists most prominently associated with this position, however, have invariably viewed IQ as the basis for determining a student's social and occupational future at an early age and providing an education to match. Thus the supposed significance of gen etic influence on IQ has invariably reflected a particular ideological view of the purpose of education and its relation to the state that is rooted in conservative political thought.