John Loehlin - Profile on Academia.edu (original) (raw)
Papers by John Loehlin
American Psychologist, 1996
In the fall of 1994, the publication of Herrnstein and Murray's book The Bell Curve sparked a new... more In the fall of 1994, the publication of Herrnstein and Murray's book The Bell Curve sparked a new round of debate about the meaning of intelligence test scores and the nature of intelligence. The debate was characterized by strong assertions as well as by strong feelings. Unfortunately, those assertions often revealed serious misunderstandings of what has (and has not) been demonstrated by scientific research in this field. Although a great deal is now known, the issues remain complex and in many cases still unresolved. Another unfortunate aspect of the debate was that many participants made little effort to distinguish scientific issues from political ones. Research findings were often assessed not so much on their merits or their scientific standing as on their supposed political implications. In such a climate, individuals who wish to make their own judgments find it hard to know what to believe. tatives. Other members were chosen by an extended consultative process, with the aim of representing a broad range of expertise and opinion.
Twin research and human genetics : the official journal of the International Society for Twin Studies, 2015
We tested a hypothesis that there is no genetic correlation between general factors of intelligen... more We tested a hypothesis that there is no genetic correlation between general factors of intelligence and personality, despite both having been selected for in human evolution. This was done using twin samples from Australia, the United States, the Netherlands, Great Britain, and Croatia, comprising altogether 1,748 monozygotic and 1,329 same-sex dizygotic twin pairs. Although parameters in the model-fitting differed among the twin samples, the genetic correlation between the two general factors could be set to zero, with a better fit if the U.S. sample was excepted.
The genetic correlation between procrastination and impulsivity
Twin research and human genetics : the official journal of the International Society for Twin Studies, 2014
The reported genetic correlation of 1.0 between the traits of procrastination and impulsivity (Gu... more The reported genetic correlation of 1.0 between the traits of procrastination and impulsivity (Gustavson, D. E., Miyake, A., Hewitt, J. K., & Friedman, N. P. (2014). Psychological Science), which was held to support an evolutionary origin of the relationship between the two traits, was tested in data from two large samples of twins from Australia. A genetic correlation of 0.299 was obtained. It was concluded that, although the presence of a genetic correlation between the two traits was supported, the modest magnitude of the correlation was such as to be consistent with many possible hypotheses, evolutionary and otherwise, about causal relationships between the traits in question.
Journal of Research in Personality, 1998
Three different measures of the Big Five personality dimensions were developed from the battery o... more Three different measures of the Big Five personality dimensions were developed from the battery of questionnaires used in the National Merit Twin Study: one from trait self-rating scales, one from personality inventory items, and one from an adjective check list. Behavior-genetic models were fit to what the three measures had in common, and to the variance distinctive to each. The
Genetic and Environmental Components of Environmental Influences
Developmental Psychology, 1985
We suggest that correlations between environmental measures and child behavior often have both ge... more We suggest that correlations between environmental measures and child behavior often have both genetic and environmental components, and we propose a simple model to test this hypothesis. Data from classical adoption studies and new data from the Colorado Adoption Project are used to illustrate the model and to provide quantitative estimates of the genetic and environmental components of environment-behavior correlations.
T he ratio of the lengths of the second to fourth digits of the hand (2D:4D) is a sexually dimorp... more T he ratio of the lengths of the second to fourth digits of the hand (2D:4D) is a sexually dimorphic trait that has been proposed as a measure of prenatal testosterone exposure and a putative correlate of a variety of later behavioral and physiological outcomes including personality, fitness and sexual orientation. We present analyses of 2D:4D ratios collected from twins (1413 individuals) and their nontwin siblings (328 individuals) from 757 families. In this sample 2D:4D was measured from photocopies using digital calipers, and for a subset of participants, computer-aided measurement. Multivariate modeling of the left-and right-hand measurements revealed significant genetic and environmental covariation between hands. The two methods yielded very similar results, and the majority of variance was explained by factors shared by both measurement methods. Neither common environmental nor dominant genetic effects were found, and the covariation between siblings could be accounted for by additive genetic effects accounting for 80% and 71% of the variance for the left and right hands, respectively. There was no evidence of sex differences in the total variance, nor in the magnitude or source of genetic and environmental influences, suggesting that X-linked effects (such as the previously identified association with the Androgen receptor) are likely to be small. However, there were also nonshared environmental effects specific to each hand, which, in addition to measurement error, may in part explain why some studies within in the literature find effects for the 2D:4D ratio of one hand but not the other.
Archives of sexual behavior, 2003
Psychological Bulletin, 1977
Two issues that complicate behavioral genetic analyses are the interaction and correlation betwee... more Two issues that complicate behavioral genetic analyses are the interaction and correlation between genetic and environmental influences. In this report, the effects of genotype-environment interaction and correlation on behavioral genetic studies (twin and adoption studies) are examined. The analysis suggests that genotype-environment interaction may bias twin study estimates of genetic and environmental influence, but need not affect adoption studies. On the other hand, genotype-environment correlation may affect both twin and adoption study estimates of genetic and environmental influence, the direction of the effect depending on the sign of the correlation. Finally, new tests of genotypeenvironment interaction and correlation, using adoption data, are proposed.
No effects of prenatal hormone transfer on digit ratio in a large sample of same- and opposite-sex dizygotic twins
Personality and Individual Differences, 2008
... Sarah E. Medland a , b , Corresponding Author Contact Information , E-mail The Corresponding ... more ... Sarah E. Medland a , b , Corresponding Author Contact Information , E-mail The Corresponding Author , John C. Loehlin c and Nicholas G. Martin a. ... There have been at least three recent studies in which the 2D:4D ratios of dizygotic (DZ) twins with same-and opposite-sex co ...
Hearing Research, 1995
Spontaneous otoacoustic emissions (SOAEs) were measured in human monozygotic (MZ) and dizygotic (... more Spontaneous otoacoustic emissions (SOAEs) were measured in human monozygotic (MZ) and dizygotic (DZ) twins and in a sample of non-twins. The number of SOAEs exhibited was more highly correlated in MZ co-twins than in same-sex DZ co-twins. Model-fitting to the correlations suggested that about three-quarters of the individual variation in the expression of SOAEs is attributable to genes. There was no convincing evidence for the heritability of specific SOAE frequencies. In accord with past surveys, SOAEs were more numerous in right than left ears, and in female than male subjects. Also investigated were the numbers of SOAEs exhibited by dark-versus light-eyed people and by MZ versus DZ twins. Those differences in our data were small and not statistically significant, but they were in a direction consistent with other studies: more SOAEs in dark-eyed individuals and in MZ twins. The view presented here is that SOAEs themselves are unlikely objects for natural selection, and probably are epiphenomena resulting from selection for those cochlear mechanisms that contribute to good hearing sensitivitywhich is related to SOAE expression. It is argued that, in addition to genetics, other factors have the potential to affect the specific numbers of SOAEs that are expressed. For example, some aspects of the complex prenatal process of producing a male fetus are presumed to be responsible for the smaller number of SOAEs seen in males than females.
Infant perception of /aba/ versus /apa/: Building a quantitative model of infant categorical discrimination
Developmental Psychology, 1992
Page 1. Developmental Psychology 1992, Vol. 28, No. 2,261-272 Copyright 1992 by the American Psyc... more Page 1. Developmental Psychology 1992, Vol. 28, No. 2,261-272 Copyright 1992 by the American Psychological Association, Inc. 0O12-1649/92/S3.0O Infant Perception of/aba/ Versus /apa/. Building a Quantitative Model of Infant Categorical Discrimination ...
Genetic and environmental components of "environmental" influences
Developmental Psychology, 1985
We suggest that correlations between environmental measures and child behavior often have both ge... more We suggest that correlations between environmental measures and child behavior often have both genetic and environmental components, and we propose a simple model to test this hypothesis. Data from classical adoption studies and new data from the Colorado Adoption Project are used to illustrate the model and to provide quantitative estimates of the genetic and environmental components of environment-behavior correlations.
Behavior Genetics, 1979
Intellectual and personality measures were available from unwed mothers who gave their children u... more Intellectual and personality measures were available from unwed mothers who gave their children up for adoption at birth. The same or similar measures have been obtained from 300 sets of adoptive parents and all of their adopted and natural children in the Texas Adoption Project. The sample characteristics are discussed in detail, and the basic findings for IQ are presented, lnitial analyses of the data on IQ suggest moderate heritabilities. Emphasis is placed on the preliminary nature of these findings.
Behavior Genetics, 1976
The equal environments hypothesis of twin methodology was examined for the variable of similarity... more The equal environments hypothesis of twin methodology was examined for the variable of similarity of appearance as it affects the personality ratings of young twins. There were two separate samples, the first with 95 pairs of same-sex twins and the second with 111 pairs. The average age of the twins in both samples was 3t/2 years. Mothers rated their twins on four personality traits and on confirmability of appearance. Not surprisingly, identical twins were markedly more similar in appearance than fraternal twins. The effect of this inequality on the personality ratings of the two types of twins was examined by correlating ratings of similarity of appearance with the absolute difference on the four personality traits for each pair of twins. None of the correlations was significant for the identical twins, suggesting that greater resemblance in appearance in identical twins does not make them more similar in personality. Indeed, the data suggested a contrast effect in which identical twins who were easily mistaken in appearance tended to be rated as less similar in personality. Thus, although similarity of appearance may create unequal environments for the two types of twins, it does not appear to bias twin studies in the direction of inflated heritabilities, at least for rating studies of the personality of young twins.
Behavior Genetics, 2007
In a replication of Turkheimer, Haley, Waldron, D'Onofrio, Gottesman II (2003, Socioeconomic stat... more In a replication of Turkheimer, Haley, Waldron, D'Onofrio, Gottesman II (2003, Socioeconomic status modifies heritability of IQ in young children. Psychological Science, 14:623-628), we investigate genotype-environment (G × E) interaction in the cognitive aptitude of 839 twin pairs who completed the National Merit Scholastic Qualifying Test in 1962. Shared environmental influences were stronger for adolescents from poorer homes, while genetic influences were stronger for adolescents from more affluent homes. No significant differences were found between parental income and parental education interaction effects. Results suggest that environmental differences between middle-to upper-class families influence the expression of genetic potential for intelligence, as has previously been suggested by Bronfenbrenner and Ceci's (1994, Nature-nurture reconceptualized in developmental perspective: a bioecological model Psychological Review, 101:568-586) bioecological model.
Blood group genes and negro-white ability differences
Behavior Genetics, 1973
... John C. Loehlin, 1 Steven G. Vandenberg, 2 and R. Travis Osborne 3 Received 10 Dec. 19 72-Fin... more ... John C. Loehlin, 1 Steven G. Vandenberg, 2 and R. Travis Osborne 3 Received 10 Dec. 19 72-Final 9 March 19 73 Data on samples of 40 and 44 Negro adolescents from two twin studies were used to test Shockley's hypothesis that blood group genes more characteristic of ...
Behavior Genetics, 1981
Children from 181 of the 300 families of the Texas Adoption Project were recontacted after a 10ye... more Children from 181 of the 300 families of the Texas Adoption Project were recontacted after a 10year interval, at an average age of 17. They completed two standard personality tests, the Minnesota Multiphasic Personality Inventory (MMPI) and the Sixteen Personality Factor Questionnaire (16PF), plus a life events questionnaire and were rated by a parent on 24 bipolar trait scales. MMPI and 16PF scores were available from the earlier study for the adoptive parents, and MMPIs were available from the agency files for many of the adopted children's birth mothers. Parent-child correlations and regressions, sibling correlations, and comparison of the means of adopted and biological children were interpreted as indicating a modest genetic influence on personality traits (narrowsense heritability, uncorrected, of about .25), a near-zero influence of shared family environmental factors, and a substantial contribution of idiosyncratic environment. The relative emotional and social adjustment of the biological and the adopted children had shifted since the time of the first study, to the detriment of the adopted children, but most still fell in the normal range.
Estimating true scores in kinship data
Behavior Genetics, 1987
Estimated true scores are occasionally used to provide an estimate of scores which would be obtai... more Estimated true scores are occasionally used to provide an estimate of scores which would be obtained if measurement error could be removed from fallible measures. When one knows only a test's relibility and an observed score for each subject, true scores are estimated by regressing observed scores toward the group mean. When relatives' observed scores are also available, estimates of true scores can be improved by using the additional information. Observed scores of subjects and relatives can be used as predictors of subjects' true scores in a multiple regression. The resulting formula is presented for the case in which only one relative's score per subject is known. Estimation of true scores for the general case ofN relatives per subject is also discussed.
Archives of Sexual Behavior, 2005
Five studies have examined the relationship between sexual orientation and the relative lengths o... more Five studies have examined the relationship between sexual orientation and the relative lengths of the 2nd and 4th fingers (the 2D:4D ratio). Although differences have commonly been found between heterosexuals and homosexuals, the direction of the difference has not been consistent across studies. The original data from all five studies were reanalyzed in a search for possible explanations of the discrepancies. Because ethnicity is known to affect the 2D:4D ratio, the reanalysis focused on participants who identified themselves as White or Caucasian, the ethnic group that was most numerous in all of the studies. Age differences did not account for the discrepancies. Differences in variability within different groups were minor. One interesting result to emerge from the reanalysis was that the 2D:4D ratios for the homosexual groups were relatively similar across studies. It was the 2D:4D values for the heterosexual participants that varied most, particularly between the USA and the British studies, and these were responsible for many of the discrepancies in the conclusions across studies. The constancy of the 2D:4D ratio for the White homosexuals did not appear to extend to homosexuals of three other ethnicities, and there were also subpopulation differences related to right or left hands.
American Psychologist, 1996
In the fall of 1994, the publication of Herrnstein and Murray's book The Bell Curve sparked a new... more In the fall of 1994, the publication of Herrnstein and Murray's book The Bell Curve sparked a new round of debate about the meaning of intelligence test scores and the nature of intelligence. The debate was characterized by strong assertions as well as by strong feelings. Unfortunately, those assertions often revealed serious misunderstandings of what has (and has not) been demonstrated by scientific research in this field. Although a great deal is now known, the issues remain complex and in many cases still unresolved. Another unfortunate aspect of the debate was that many participants made little effort to distinguish scientific issues from political ones. Research findings were often assessed not so much on their merits or their scientific standing as on their supposed political implications. In such a climate, individuals who wish to make their own judgments find it hard to know what to believe. tatives. Other members were chosen by an extended consultative process, with the aim of representing a broad range of expertise and opinion.
Twin research and human genetics : the official journal of the International Society for Twin Studies, 2015
We tested a hypothesis that there is no genetic correlation between general factors of intelligen... more We tested a hypothesis that there is no genetic correlation between general factors of intelligence and personality, despite both having been selected for in human evolution. This was done using twin samples from Australia, the United States, the Netherlands, Great Britain, and Croatia, comprising altogether 1,748 monozygotic and 1,329 same-sex dizygotic twin pairs. Although parameters in the model-fitting differed among the twin samples, the genetic correlation between the two general factors could be set to zero, with a better fit if the U.S. sample was excepted.
The genetic correlation between procrastination and impulsivity
Twin research and human genetics : the official journal of the International Society for Twin Studies, 2014
The reported genetic correlation of 1.0 between the traits of procrastination and impulsivity (Gu... more The reported genetic correlation of 1.0 between the traits of procrastination and impulsivity (Gustavson, D. E., Miyake, A., Hewitt, J. K., & Friedman, N. P. (2014). Psychological Science), which was held to support an evolutionary origin of the relationship between the two traits, was tested in data from two large samples of twins from Australia. A genetic correlation of 0.299 was obtained. It was concluded that, although the presence of a genetic correlation between the two traits was supported, the modest magnitude of the correlation was such as to be consistent with many possible hypotheses, evolutionary and otherwise, about causal relationships between the traits in question.
Journal of Research in Personality, 1998
Three different measures of the Big Five personality dimensions were developed from the battery o... more Three different measures of the Big Five personality dimensions were developed from the battery of questionnaires used in the National Merit Twin Study: one from trait self-rating scales, one from personality inventory items, and one from an adjective check list. Behavior-genetic models were fit to what the three measures had in common, and to the variance distinctive to each. The
Genetic and Environmental Components of Environmental Influences
Developmental Psychology, 1985
We suggest that correlations between environmental measures and child behavior often have both ge... more We suggest that correlations between environmental measures and child behavior often have both genetic and environmental components, and we propose a simple model to test this hypothesis. Data from classical adoption studies and new data from the Colorado Adoption Project are used to illustrate the model and to provide quantitative estimates of the genetic and environmental components of environment-behavior correlations.
T he ratio of the lengths of the second to fourth digits of the hand (2D:4D) is a sexually dimorp... more T he ratio of the lengths of the second to fourth digits of the hand (2D:4D) is a sexually dimorphic trait that has been proposed as a measure of prenatal testosterone exposure and a putative correlate of a variety of later behavioral and physiological outcomes including personality, fitness and sexual orientation. We present analyses of 2D:4D ratios collected from twins (1413 individuals) and their nontwin siblings (328 individuals) from 757 families. In this sample 2D:4D was measured from photocopies using digital calipers, and for a subset of participants, computer-aided measurement. Multivariate modeling of the left-and right-hand measurements revealed significant genetic and environmental covariation between hands. The two methods yielded very similar results, and the majority of variance was explained by factors shared by both measurement methods. Neither common environmental nor dominant genetic effects were found, and the covariation between siblings could be accounted for by additive genetic effects accounting for 80% and 71% of the variance for the left and right hands, respectively. There was no evidence of sex differences in the total variance, nor in the magnitude or source of genetic and environmental influences, suggesting that X-linked effects (such as the previously identified association with the Androgen receptor) are likely to be small. However, there were also nonshared environmental effects specific to each hand, which, in addition to measurement error, may in part explain why some studies within in the literature find effects for the 2D:4D ratio of one hand but not the other.
Archives of sexual behavior, 2003
Psychological Bulletin, 1977
Two issues that complicate behavioral genetic analyses are the interaction and correlation betwee... more Two issues that complicate behavioral genetic analyses are the interaction and correlation between genetic and environmental influences. In this report, the effects of genotype-environment interaction and correlation on behavioral genetic studies (twin and adoption studies) are examined. The analysis suggests that genotype-environment interaction may bias twin study estimates of genetic and environmental influence, but need not affect adoption studies. On the other hand, genotype-environment correlation may affect both twin and adoption study estimates of genetic and environmental influence, the direction of the effect depending on the sign of the correlation. Finally, new tests of genotypeenvironment interaction and correlation, using adoption data, are proposed.
No effects of prenatal hormone transfer on digit ratio in a large sample of same- and opposite-sex dizygotic twins
Personality and Individual Differences, 2008
... Sarah E. Medland a , b , Corresponding Author Contact Information , E-mail The Corresponding ... more ... Sarah E. Medland a , b , Corresponding Author Contact Information , E-mail The Corresponding Author , John C. Loehlin c and Nicholas G. Martin a. ... There have been at least three recent studies in which the 2D:4D ratios of dizygotic (DZ) twins with same-and opposite-sex co ...
Hearing Research, 1995
Spontaneous otoacoustic emissions (SOAEs) were measured in human monozygotic (MZ) and dizygotic (... more Spontaneous otoacoustic emissions (SOAEs) were measured in human monozygotic (MZ) and dizygotic (DZ) twins and in a sample of non-twins. The number of SOAEs exhibited was more highly correlated in MZ co-twins than in same-sex DZ co-twins. Model-fitting to the correlations suggested that about three-quarters of the individual variation in the expression of SOAEs is attributable to genes. There was no convincing evidence for the heritability of specific SOAE frequencies. In accord with past surveys, SOAEs were more numerous in right than left ears, and in female than male subjects. Also investigated were the numbers of SOAEs exhibited by dark-versus light-eyed people and by MZ versus DZ twins. Those differences in our data were small and not statistically significant, but they were in a direction consistent with other studies: more SOAEs in dark-eyed individuals and in MZ twins. The view presented here is that SOAEs themselves are unlikely objects for natural selection, and probably are epiphenomena resulting from selection for those cochlear mechanisms that contribute to good hearing sensitivitywhich is related to SOAE expression. It is argued that, in addition to genetics, other factors have the potential to affect the specific numbers of SOAEs that are expressed. For example, some aspects of the complex prenatal process of producing a male fetus are presumed to be responsible for the smaller number of SOAEs seen in males than females.
Infant perception of /aba/ versus /apa/: Building a quantitative model of infant categorical discrimination
Developmental Psychology, 1992
Page 1. Developmental Psychology 1992, Vol. 28, No. 2,261-272 Copyright 1992 by the American Psyc... more Page 1. Developmental Psychology 1992, Vol. 28, No. 2,261-272 Copyright 1992 by the American Psychological Association, Inc. 0O12-1649/92/S3.0O Infant Perception of/aba/ Versus /apa/. Building a Quantitative Model of Infant Categorical Discrimination ...
Genetic and environmental components of "environmental" influences
Developmental Psychology, 1985
We suggest that correlations between environmental measures and child behavior often have both ge... more We suggest that correlations between environmental measures and child behavior often have both genetic and environmental components, and we propose a simple model to test this hypothesis. Data from classical adoption studies and new data from the Colorado Adoption Project are used to illustrate the model and to provide quantitative estimates of the genetic and environmental components of environment-behavior correlations.
Behavior Genetics, 1979
Intellectual and personality measures were available from unwed mothers who gave their children u... more Intellectual and personality measures were available from unwed mothers who gave their children up for adoption at birth. The same or similar measures have been obtained from 300 sets of adoptive parents and all of their adopted and natural children in the Texas Adoption Project. The sample characteristics are discussed in detail, and the basic findings for IQ are presented, lnitial analyses of the data on IQ suggest moderate heritabilities. Emphasis is placed on the preliminary nature of these findings.
Behavior Genetics, 1976
The equal environments hypothesis of twin methodology was examined for the variable of similarity... more The equal environments hypothesis of twin methodology was examined for the variable of similarity of appearance as it affects the personality ratings of young twins. There were two separate samples, the first with 95 pairs of same-sex twins and the second with 111 pairs. The average age of the twins in both samples was 3t/2 years. Mothers rated their twins on four personality traits and on confirmability of appearance. Not surprisingly, identical twins were markedly more similar in appearance than fraternal twins. The effect of this inequality on the personality ratings of the two types of twins was examined by correlating ratings of similarity of appearance with the absolute difference on the four personality traits for each pair of twins. None of the correlations was significant for the identical twins, suggesting that greater resemblance in appearance in identical twins does not make them more similar in personality. Indeed, the data suggested a contrast effect in which identical twins who were easily mistaken in appearance tended to be rated as less similar in personality. Thus, although similarity of appearance may create unequal environments for the two types of twins, it does not appear to bias twin studies in the direction of inflated heritabilities, at least for rating studies of the personality of young twins.
Behavior Genetics, 2007
In a replication of Turkheimer, Haley, Waldron, D'Onofrio, Gottesman II (2003, Socioeconomic stat... more In a replication of Turkheimer, Haley, Waldron, D'Onofrio, Gottesman II (2003, Socioeconomic status modifies heritability of IQ in young children. Psychological Science, 14:623-628), we investigate genotype-environment (G × E) interaction in the cognitive aptitude of 839 twin pairs who completed the National Merit Scholastic Qualifying Test in 1962. Shared environmental influences were stronger for adolescents from poorer homes, while genetic influences were stronger for adolescents from more affluent homes. No significant differences were found between parental income and parental education interaction effects. Results suggest that environmental differences between middle-to upper-class families influence the expression of genetic potential for intelligence, as has previously been suggested by Bronfenbrenner and Ceci's (1994, Nature-nurture reconceptualized in developmental perspective: a bioecological model Psychological Review, 101:568-586) bioecological model.
Blood group genes and negro-white ability differences
Behavior Genetics, 1973
... John C. Loehlin, 1 Steven G. Vandenberg, 2 and R. Travis Osborne 3 Received 10 Dec. 19 72-Fin... more ... John C. Loehlin, 1 Steven G. Vandenberg, 2 and R. Travis Osborne 3 Received 10 Dec. 19 72-Final 9 March 19 73 Data on samples of 40 and 44 Negro adolescents from two twin studies were used to test Shockley's hypothesis that blood group genes more characteristic of ...
Behavior Genetics, 1981
Children from 181 of the 300 families of the Texas Adoption Project were recontacted after a 10ye... more Children from 181 of the 300 families of the Texas Adoption Project were recontacted after a 10year interval, at an average age of 17. They completed two standard personality tests, the Minnesota Multiphasic Personality Inventory (MMPI) and the Sixteen Personality Factor Questionnaire (16PF), plus a life events questionnaire and were rated by a parent on 24 bipolar trait scales. MMPI and 16PF scores were available from the earlier study for the adoptive parents, and MMPIs were available from the agency files for many of the adopted children's birth mothers. Parent-child correlations and regressions, sibling correlations, and comparison of the means of adopted and biological children were interpreted as indicating a modest genetic influence on personality traits (narrowsense heritability, uncorrected, of about .25), a near-zero influence of shared family environmental factors, and a substantial contribution of idiosyncratic environment. The relative emotional and social adjustment of the biological and the adopted children had shifted since the time of the first study, to the detriment of the adopted children, but most still fell in the normal range.
Estimating true scores in kinship data
Behavior Genetics, 1987
Estimated true scores are occasionally used to provide an estimate of scores which would be obtai... more Estimated true scores are occasionally used to provide an estimate of scores which would be obtained if measurement error could be removed from fallible measures. When one knows only a test's relibility and an observed score for each subject, true scores are estimated by regressing observed scores toward the group mean. When relatives' observed scores are also available, estimates of true scores can be improved by using the additional information. Observed scores of subjects and relatives can be used as predictors of subjects' true scores in a multiple regression. The resulting formula is presented for the case in which only one relative's score per subject is known. Estimation of true scores for the general case ofN relatives per subject is also discussed.
Archives of Sexual Behavior, 2005
Five studies have examined the relationship between sexual orientation and the relative lengths o... more Five studies have examined the relationship between sexual orientation and the relative lengths of the 2nd and 4th fingers (the 2D:4D ratio). Although differences have commonly been found between heterosexuals and homosexuals, the direction of the difference has not been consistent across studies. The original data from all five studies were reanalyzed in a search for possible explanations of the discrepancies. Because ethnicity is known to affect the 2D:4D ratio, the reanalysis focused on participants who identified themselves as White or Caucasian, the ethnic group that was most numerous in all of the studies. Age differences did not account for the discrepancies. Differences in variability within different groups were minor. One interesting result to emerge from the reanalysis was that the 2D:4D ratios for the homosexual groups were relatively similar across studies. It was the 2D:4D values for the heterosexual participants that varied most, particularly between the USA and the British studies, and these were responsible for many of the discrepancies in the conclusions across studies. The constancy of the 2D:4D ratio for the White homosexuals did not appear to extend to homosexuals of three other ethnicities, and there were also subpopulation differences related to right or left hands.
Latent variable models: An introduction to factor, path, and structural equation analysis (5th ed.)