LETTERS TO AND FROM THE EDITOR Dear Sir: We feel it is necessary to correct a misleading impression given by Professor Jensen in his article, "The Phylogeny and Ontogeny of Intelligence" [I]. Jensen writes, "It is now generally accepted by geneticists, psychologists, and sociologists who have reviewed the evidence that social class differences in mental abilities have a substantial genetic component." This statement should be considered in rela- ' tion to the following facts which at least many geneticists would accept: (i) The proportion of the IQ variance that arises from genetic variety in a population is less than 100 percent, (ii) IQ is a continuous variable, and it is not yet possible to determine gene frequencies, (iii) It follows "that we cannot at present answer the question whether there is any genetic component of social class or race differences in mean IQ" [2]. It is also impossible to say whether there is any environmental component, for this is, in fact, the same question. Thus, as it is impossible to quantify either the genetic or the environmental component of social class differences in mean IQ, we feel it is unwise to say that there is "a substantial genetic component" in these differences. We find it disturbing that Jensen chooses to ignore these facts. REFERENCES 1.A. R.Jensen. Perspect. Biol. Med., 15:37, 1971. 2.J. M. Thoday. J. Biosoc. Sci., 1 (suppl.):3, 1969. John B. Gibson C. G. Nicholas Mascie-Taylor James N. Thompson, Jr. Department of Genetics University of Cambridge Cambridge, England Dear Sir: The first two statements listed by Gibson, Mascie-Taylor, and Thompson are certainly true. I disagree, however, with their third point. It is not a necessary condition either that there be 100 percent heritability of IQ or that we must be able to count single gene frequencies in order statistically to infer with a high degree of probability the existence of a genetic component in the mean IQ difference among socioeconomic classes. (I am here referring to social class differences within a given racial group. The question of intelligence differences between racial groups involves other methodological problems and types of evidence not discussed here.) 154 I Letters to and from the Editor Several lines of evidence support with a high level of confidence the conclusions that social classes, on the average, differ to some degree in the genetic factors involved in intellectual development. Social classes may be viewed as Mendelian populations that have diverged genetically. When the population is stratified into five or six socioeconomic status (SES) categories, mainly according to occupational criteria, the mean IQs of the adults so classified, from the highest SES category (professional and managerial) to the lowest (unskilled labor), span a range of some 30-40 points. The standard deviation of IQs within SES groups averages about 9 or 10 points for the adult population, as compared with SD = 15 for the whole population. Children born into these SES groups, on the other hand, show a mean IQ difference, from the lowest to the highest class, of only 20-30 points; and the SD within classes for children is about 13 or 14 IQ points, which means there is almost as much IQ variation among children within social classes as we find in the total population. The cause of the higher degree of correlation between SES and IQ among adults than among children is the high level of social mobility in each generation. In England and in the United States more than 30 percent of the adult generation are found to be of a different SES than that of their own parents [1-3]. In each generation some individuals move up in SES and some move down. Those who move up have higher IQs, on the average, than those who move down. Since the heritability, h2 (i.e., the proportion of genetic variance), of IQ in the total population is between .70 and .80, and since the correlation between phenotypes and genotypes is the square root of the heritability, it follows that IQ estimates genotypic intelligence with a reliability of between -y/_jÖ and vT8Ö (i.e., between about .84 and .89 [4, 5]). Conversely, the reliability with which...
Studies in different countries, which have shown that rates of mobility are more alike than they were expected to be, have raised questions about the mechanisms underlying social mobility. The following paper puts forward the suggestion that social mobility belongs to a cybernetic mechanism whereby something like a ‘steady state’ is maintained in each occupational class by means of constant movement into and out of it. The quality discussed is ‘intelligence’; and the argument stems from two main observations. The first is that the higher the occupational class, the higher is the measured intelligence. The second is that the children of parents towards the extreme show a ‘regression’ from that extreme towards the mean of the general population. If these two observations hold true over a period of time, it follows that there must be social mobility. In a third part of the paper it is argued that differential fertility between the classes gives rise to additional mobility. The last section discusses longer‐term changes which may influence the amplitude of short‐term oscillations between any two generations, and finally notes a certain parallelism with the laws of thermodynamics.
Summary A study has been made in a group of rural Oxfordshire villages of levels of similarity between husbands and wives for IQ, personality and some anthropometric characteristics. Significant levels of assortative marriage have been found in both verbal and performance IQ, personality ‘inconsistency’, stature, weight and some other bodily dimensions. Their nature has been analysed by time of marriage, birthplace and social class, all of which appear to have marked effects. On the other hand, length of courtship and distance apart of the partners' residences at marriage seem to be more or less inconsequential.
The patterns of serological polymorphic variety in a group of Oxfordshire populations are related to previously made demographic predictions that the different villages and social classes might be expected to be genetically homogeneous if movement were the main factor determining genetic structure. The predictions are largely fulfilled though there remains a residual pattern of variety which is detectable when all the systems tested are considered together by "genetic distance" examination, and in the case of the geographic variation this pattern reflects the comparative magnitude of the exchanges between the different villages.
The drinking, smoking, and drug-taking patterns of 9829 adult members of the Australian Workers Union in Sydney are compared with data collected through the Medicheck Referral Centre. Overall, the two sets of data are very similar, but the results of this survey point to the high prevalence of heavy alcohol consumption, and of regular drug-taking in young people.
Summary Examination of 150 husband–wife pairs from the Otmoor villages of Oxfordshire for levels of similarity in their performance of seven subtests of the WAIS IQ test showed significant positive correlation in five subtests but not in digit span or digit symbol. In no test was there any relation between level of spouse similarity and length of marriage. Scores were varyingly associated with several factors known to be related to total IQ, such as social class and nature of education. When the effects of these factors on IQ variation were removed statistically most of the spouse similarity disappeared. However there remained a significant residual similarity in vocabulary performance and some suggestion of one in similarities and block design.
Pseudorandom sweeps have very desirable correlation properties that make them promising candidates for use in simultaneous sourcing. Such sweeps are also attractive for generating low frequencies that are more regularly being sought by the industry. Recently there has been considerable interest in acquiring seismic data sets with good low frequency content. Typically a 30‐dB/octave barrier must be overcome to recover useful low frequency energy. Low‐dwell nonlinear sweeps compatible with vibrator mechanical constraints have been recently introduced as one way to address the challenges of low frequency, but special pseudorandom sweeps provide another viable option. Pseudorandom sweeps reduce the peak demands on the vibrator and can become more effective as the start frequency for the sweep is lowered. Analysis of field test data show that frequencies as low as 2 Hz can be recovered with useable signal‐to‐noise at reasonable fold.
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