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Thread: Comparative IQ and Brain Size Data

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    Ha, so very true; brain size is no reliable indicator for intelligence. Of course, that's not to say you can get by with one the size of an egg.

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    Post Does Brain size matter?

    Does Brain size matter? A Reply to Rushton and Ankney

    by MICHAEL PETERS
    , University of Guelph


    Rushton and Ankney (1995) suggest that I was in error when
    rejecting the claim (Lynn, 1993) that a relation between brain size
    and intelligence is firmly established. Since my note went to press
    (Peters, 1993), several papers have appeared which indicate a sizeable
    relation between brain size, as determined by mri scan, and IQ
    (Andreasen, Flaum, Swayze, O'Leary, Alliger, Cohen, Ehrhardtm, &
    Yuhet, 1993; Egan, Chiswick, Santosh, Naidu, Rimmington, & Bestet,
    1994; Raz, Torres, Spencer, Millman, Baertschi, & Sarpel, 1993;
    Wickett, Vernon, & Lee, 1994). Each of the above studies has some
    problems posed by method and interpretations or by the findings
    themselves. For example, Egan et al. found the highest correlation not
    between brain matter and IQ, but between cerebrospinal fluid volume
    and IQ (r = .8), an inexplicable result for those who argue that it is
    brain matter which is correlated with IQ. Nevertheless, as a group,
    these studies justify the conclusion that there is a positive and
    sizable correlation between brain size and IQ. This lends credibility
    to earlier claims by Willerman, Schultz, Rutledge, & Bigler, 1991;
    1992) and supports Rushton & Ankney's critIQue. The new mri data are
    important because studies that relate IQ to brain size as estimated
    through cranial parameters remain contradictory. For example, Reed and
    Jensen (1993) report an equivalent cranial capacity of 1550 cm3 for a
    high IQ group (124-136) and 1549 cm3 for a low IQ group (87-111),
    whereas studies listed by Wickett et al. (1994) report positive
    correlations between cranial capacity and IQ.

    Accepting the fact that MRI data document a significant correlation
    between brain size and intelligence within demographically homogeneous
    groups, the question of causality arises. Neural systems, by
    definition, have evolved to interact with the environment, and the
    very significant expansion of brain size after birth, driven by a
    growth of synapses and cortical interconnections, is interactive with
    environmental input (Bedi, Massey, & Smart, 1989; Jacobsen, 1991, pp.
    266-270; Walsh, 1981). Thus, nutritional and environmental conditions
    which foster good development of intelligence can be expected to
    foster good physical brain development as well. My seemingly
    nonsensical position, that under some conditions it is useful to
    control for body size when looking at brain/IQ relations, is based on
    the possibility that the relation between brain size and IQ is
    confounded by nutritional and environmental conditions (cf.
    Passingham, 1979; Rodriguez, Donnadien, Martinez, & Chavez, 1979).
    This does not change the basic observations, but it does change
    arguments about causation.

    Sex, IQ and brain size

    Rushton & Ankney reiterate the conclusion, already reached by Gould
    (1981, p. 106), that women have absolutely much smaller, and
    relatively somewhat smaller brains than men. I continue to disagree
    with Rushton & Ankney on the issue of scaling. The statement that
    allometric technIQues standard in comparative biology have been used
    does not assure that these are appropriately used for between sex
    comparisons. In the available brain size/IQ studies, the differences
    in IQ are small or non-existent (Passingham, 1979; Raz et al., 1993;
    Willerman et al., 1991), in spite of very large differences in brain
    size. Three interpretations offer themselves: (a) women do have lower
    IQ's than men after all (Lynn, 1994), (b) the gross brain size in
    women is not a meaningful index for comparison because of difficulties
    in scaling body/brain parameters across sexes and possible differences
    in fine structure (Peters, 1991; Willerman et al., 1991), and (c)
    women and men differ especially on specific spatial tasks (Rushton &
    Ankney, 1995). Because most of the mri evidence is cast in terms of
    standard IQ test/brain size relations, it is interesting to note that
    the sex differences in Wechsler IQ which are summarized by Lynn are
    very small relative to the sex differences in brain size. This
    supports interpretation (b). Rushton & Ankney's point (c) is difficult
    to evaluate at this point. Rushton & Ankney emphasize spatial ability,
    and point out that there are significant sex differences in 3-d
    spatial abilities, especially mental rotation performance. However,
    Wickett et al. find no significant correlation between brain size and
    mental rotation performance in their sample of women, and considerably
    lower correlations between Wechsler performance IQ and brain size than
    for Wechsler verbal IQ and brain size. Caution is advised in
    attributing spatial performance to brain size or neuron counts because
    such performance is very sensitive to practice; women can improve
    their mental rotation performance by 30% to 50 % (Peters, Chisholm, &
    Laeng, 1995) after only a single exposure to the test. Such rapid
    improvement is difficult to reconcile with the idea that brain size,
    within normal limits, is the limiting factor in 3-d spatial
    performance.

    Race and IQ differences

    Rushton and Ankney (1995) classify races into three groups, and this
    has been a source of contention (e.g., Weizmann et al., 1990). The
    issue of race classification is a major problem in anthropology
    (Harrison, Tanner, Pilbeam, & Baker, 1988; p. 326) and cannot be
    addressed here. Rushton & Ankney have adopted an essentially
    operational definition that shares the strengths and weaknesses of
    such definitions. To simplify things, I shall adopt the terms
    Caucasoid, Mongoloid, and Negroid when referring to the data in
    Rushton's work.

    Much of Rushton and Ankney's (1995) case on racial differences in
    brain size is based on estimates derived from cranial measures. Such
    estimates are not without problems (Hoadley & Pearson, 1929; Wickett
    et al., 1994, Willerman et al., 1991), and may have different validity
    for men and women. As an illustration, Willerman et al. (1992), found
    a significant correlation between brain size and head perimeter for
    women, but not for men. Nevertheless, let us assume that cranial
    measures do provide an imperfect but acceptable estimate of brain
    size. Rushton & Ankney encounter several problems in the attempt to
    generalize the mri/brain size/IQ data to the general context of racial
    comparisons. One of the problems lies in the simplified grouping of
    races, because this tends to give insufficient weight to within- group
    variations.

    Rushton's (1991) own data illustrate the point. Within the Caucasoid
    grouping, a 1969 sample of Iranian soldiers is given an average
    estimated cranial capacity of 1356 cm3, whereas a 1966 sample of
    American Army soldiers has an average of 1470 cm3. Similarly, a 1967
    us Air Force sample has 1539 cm3, whereas a 1975 German Air Force
    sample has 1455 cm3. Within the Mongoloid grouping, a 1963 sample of
    Thai soldiers has an estimated average of 1340 cm3, whereas a 1965
    sample of South Vietnamese has 1299 cm3. All of these differences are
    much larger than the differences obtained between Negroid (1449 cm3),
    Caucasoid (1468 cm3), and Mongol- oid (1464 cm3) enlisted men from a
    1988 us Army cohort using Rushton's (1992) terms and data. There are
    also secular changes within a culture and racial group (Haug, 1984;
    Miller & Corsellis, 1977). For example, us Air Force personnel
    measured in 1967 had estimated brain sizes that exceeded by 68 cm3
    values from a us Air Force sample drawn in 1950 (Rushton, 1991). In
    face of such variation within groupings, between cultures for similar
    groupings, and between different cohorts drawn within a culture,
    generally valid statements about race differences are difficult to
    make.

    Two additional points need to be made. Rushton and Ankney (1995)
    suggest that cranial capacity estimates for Mongoloid-, Caucasoid-,
    and Negroid-Americans are 1416, 1380, and 1359 cm3, respectively,
    indicating larger differences than Rushton's (1992) values given above
    for these groups (1464, 1468, 1449cm3). The former values for the
    three groups represent cranial capacity estimates which are based on
    values corrected for body parameters (Rushton, 1992). To perform this
    correction, Rushton used slopes for the log/log plot of brain against
    body weight which are not appropriate for within- species comparisons
    (Harvey, 1988). For comparison of individuals drawn from the same
    species, a slope which is almost horizontal is appropriate, and should
    be close to the .08 determined empirically by Reed and Jensen (1993).
    This is borne out by other available evidence. Wickett et al. (1994)
    state that for their sample of white women, it would appear that the
    size of the brain is largely independent of body size (p. 836).
    Similarly, Jerison (1979) found no significant association between
    body weight or height and brain weight for men within the age range of
    29 to 41 years of age. A conservative conclusion is that there is no
    legitimate reason for using steep slopes in comparing brain/body size
    relations across races. As a result, statements about brain size
    differences between races should not rely on adjusted values, and it
    is not appropriate to conclude that higher IQ's in Asians are linked
    to larger brain size.

    The issue of race/brain size/IQ invites a return to the sex/brain
    size/IQ issue. Rushton's (1992) data show that the estimated cranial
    capacity of Negroid-American men is some 13-14% higher than that of
    Caucasoid-American women, even though the average IQ for the former is
    presumably lower. How can this be integrated into a model of larger
    brain => higher IQ without qualifying the meaning of brain size
    comparisons across sexes, or revisiting the issue of what factors
    other than brain size have a bearing on IQ? This question once again
    emphasizes the unresolved issues of how brain weight/ body parameters
    can be compared across sexes, races, and age cohorts.

    Finally, the small absolute differences in brain size between
    Mongoloids, Caucasoids, and Negroids in Rushton's (1992) data base
    should be evaluated relative to cohort data. We have seen that values
    from two Air Force samples drawn 17 years apart showed estimated brain
    size differences that are larger than the differences reported between
    races in the 1988 common age cohort. It is legitimate to ask whether
    the contemporary Negroid- and Caucasoid-American samples described in
    the common 1988 age cohort could not differ as much from each other in
    undefined demographic and nutritional variables as the cohort samples
    from 1950 and 1967 differed from each other.

    I am not going to address the issue of racial differences in IQ
    relative to brain size, because this cannot be resolved here. Clearly,
    Rushton & Ankney feel that sufficient evidence is available to make
    their point on racial differences in IQ. The issue is not whether such
    differences can be observed; they are observed and they are marked and
    important for a number of reasons. What to make of them is another
    matter. If cohort differences across time and culture complicate
    interpretation of brain size differences across races, the additional
    uncontrolled effects of community variables in the determination of IQ
    (Church & Katigbak, 1991; Coon, Carey & Fulker, 1992; Wachs, Moussa,
    Bishry, Yunis, Sobhy, McCabe, Jerome, Galal, Harrison, & Kirksley,
    1993) across races render conclusive statements about racial IQ
    differences even more difficult, if not impossible at present.



    References


    Andreasen, N.C., Flaum, M., Swayze, V., O'Leary, D.S., Alliger, R.,
    Cohen, G., Ehrhardt, J., Yuh, W.T.C. (1993). Intelligence and brain
    structure in normal individuals. American Journal of Psychiatry, 150,
    130-134.

    Bedi, K.S., Massey, R.F., & Smart, J.L. (1989). Neuronal and synaptic
    measure- ments in the visual cortex of adults after undernutrition
    during normal or artificial rearing. Journal of Comparative Neurology,
    289, 89-98.

    Church, A.T., & Katigbak, M.S. (1991). Home environment, nutritional
    status, and maternal intelligence as determinants of intellectual
    development in rural Philippine preschool children. Intelligence, 15,
    49-78.

    Coon, H., Carey, G., & Fulker, D.W. (1992). Community influences on
    cognitive ability. Intelligence, 16, 169-188.

    Egan, V., Chiswick, A., Santosh, C., Naidu, K., Rimmington, J.E., &
    Best, J.J.K. (1994). Size isn't everything: a study of brain volume,
    intelligence and auditory potentials. Personality and Individual
    Differences, 17, 357-367.

    Gould, S.J. (1981). The mismeasure of man. New York: W.W. Norton.

    Harrison, G.A., Tanner, J.M., Pilbeam, D.R., & Baker, P.T. (1988).
    Human Biology. Oxford: Oxford University Press.

    Harvey, P.H. (1988). Allometric analysis and brain size. In H.J.
    Jerison & I. Jerison (Eds.), Intelligence and evolutionary biology
    (pp. 199-210). Berlin: Springer Verlag.

    Haug, H. (1984). Der Einfluss der s„kularen Akzeleration auf das
    Hirngewicht des Menschen und dessen Žnderung w„hrend der Alterung.
    Gegenbaurs morphologisches Jahrbuch, 130, 481-500.

    Hoadley, M.F., & Pearson, K. (1929). On measurement of the internal
    diameter of the skull in relation, I to the prediction of its capacity
    and, II to the `pre-eminence' of the left hemisphere. Biometrika, 21,
    85-123.

    Jacobsen, M. (1991). Developmental Neurobiology. New York: Plenum
    Press.

    Jerison, H.J. (1979). The evolution of diversity in brain size. In
    M.E. Hahn, C. Jensen, & B.C. Dudek (Eds.) Development and evolution in
    brain size (pp. 29-57). New York: Academic Press.

    Lynn, R. (1994). Sex differences in intelligence and brain size: a
    paradox resolved. Personality and Individual Differences, 17, 257-271.

    Lynn, R. (1993). Brain size and intelligence in man: a correction to
    Peters. Canadian Journal of Experimental Psychology, 47, 748-750.

    Miller, A.K.H., & Corsellis, J.A.N. (1977). Evidence for a secular
    increase in human brain weight during the past century. Annals of
    Human Biology, 4, 253-257.

    Passingham, R.E. (1979) Brain size and intelligence in man. Brain,
    Behavior and Evolution, 16, 253-270.

    Peters, M. (1991). Sex Differences in Human Brain Size and the General
    Meaning of Differences in brain size. Canadian Journal of Psychology,
    45, 507-522.

    Peters, M. (1993). Still no convincing evidence of a relation between
    brain size and intelligence in humans. Canadian Journal of
    Experimental Psychology, 47, 751-756.

    Peters, M., Chisholm, P., & Laeng, B. (1995). Spatial ability, student
    gender and academic performance. Journal of Engineering Education, 84,
    69-73.

    Raz, N., Torres, I.J., Spencer, W.D., Millman, D., Baertschi, J.C., &
    Sarpel, G. (1993). Neuroanatomical correlates of age-sensitive and
    age-invariant cognitive abilities: an in vivo mri investigation.
    Intelligence, 17, 407-422.

    Reed, T.E., & Jensen, A.R. (1993). Cranial capacity: new Caucasian
    data and comments on Rushton's claimed Mongoloid-Caucasoid brain-size
    differences. Intelligence, 17, 423-431.

    Rodriguez, R., Donnadien, F.R., Martinez, C., & Chavez, A. (1979).
    Nutrition and development of children from poor rural areas. viii. The
    effect of mild malnutri- tion on children's neurological development.
    Nutrition Reports International, 19, 315-326.

    Rushton, J.P. (1991). Mongoloid-caucasoid differences in brain size
    from military samples. Intelligence, 15, 351-359.

    Rushton, J.P. (1992). Cranial capacity related to sex, rank and race
    in a stratified random sample of 6325 u.s. military personnel.
    Intelligence, 16, 401-413.

    Wachs, T.D., Moussa, W., Bishry, Z., Yunis, F., Sobhy, A., McCabe, G.,
    Jerome, N., Galal, O., Harrison, G., & Kirksley, A. (1993). Relations
    between nutrition and cognitive performance in Egyptian toddlers.
    Intelligence, 17, 151-172.

    Walsh, R.N. (1981). Effects of environmental complexity and
    deprivation on brain anatomy and histology. International Journal of
    Neuroscience, 12, 33-51.

    Weizmann, F., Wiener, N.I., & Wiesenthal, D.L., & Ziegler, M. (1990).
    Differential K theory and racial hierarchies. Canadian Psychology, 31,
    1-13.

    Wickett, J.C., Vernon, P.A., & Lee, D.H. (1994). In vivo brain size,
    head per- imeter, and intelligence in a sample of healthy adult
    females. Personality and Individual Differencess, 16, 831-838.

    Willerman, L., Schultz, R., Rutledge, & Bigler, E.D. (1991). In vivo
    brain size and intelligence. Intelligence, 15, 223-228.

    Willerman, L., Schultz, R., Rutledge, N.J., & Bigler, E.D. (1992).
    Hemisphere size asymmetry predicts relative verbal and nonverbal
    intelligence differently in the sexes: an mri study of
    structure-function relations. Intelligence, 16, 315-328.

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    Post Brain Size Matters: A Reply to Peters

    Brain Size Matters: A Reply to Peters

    J. PHILIPPE RUSHTON and C. DAVISON ANKNEY

    University of Western Ontario

    Abstract

    Peters (1993) claimed that published research on brain size and
    IQ is flawed because it did not meet his list of minimum
    conditions that (a) subjects should be matched for height, weight
    and age, (b) analyses should be conducted separately within sex,
    (c) subjects should not vary in prenatal and nutritional history,
    (d) people with IQs appreciably below the population mean of 100
    should not be studied, and (e) brain size measures should be done
    blind . However, these conditions have either been met or are
    unnecessary and/or inappropriate. We show, contrary to Peters'
    claims, that (a) brain size is related to mental abilities, (b)
    brain size varies by sex and race, and (c) mental abilities vary
    by sex and race. Finally, we suggest that brain size constraints
    on behavioural complexity may be best understood from an
    evolutionary perspective.

    In a reply to Lynn (1993) about brain size and IQ, Peters (1993)
    charged bias and questionable motives to dismiss relations first
    established over 100 years ago. Peters (1993) claimed that studies of
    brain size are confounded by systematic bias, including racial bias ,
    over and above normal measurement error. Peters (1993) also
    conjectured that uni-directional measurement errors may exist and so
    he dismissed Rushton's (1992) analyses showing race and sex
    differences in cranial capacity in 6,325 U.S. military personnel.
    Consequently, Peters claimed that such studies must be done blind ,
    i.e., the person doing the measurement should not know the race of the
    subject being measured.

    Peters did not note, although it was made clear in Rushton's (1992)
    paper, that (1) Rushton neither made the measurements nor knew who
    did, and (2) measurements were made to determine proper helmet sizes
    not brain sizes (i.e., they were done blind , as the measurers were
    unaware of the use that Rushton would make of their data). The East
    Asian/European/African differences that Rushton (1992) found in
    cranial capacity (cm3) using external head measurements are similar to
    those found by Beals, Smith, and Dodd (1984) who estimated cm3 from
    endocranial volume, and by Ho, Roessmann, Straumfjord, and Monroe
    (1980) who weighed brain mass (grams) at autopsy. Does Peters believe
    that Ho et al. leaned on their scales, when weighing brains of
    European-Americans, by just enough to produce the same difference
    caused by extra snug measurements supposedly made by those measuring
    heads of African-Americans? Regardless, it is implausible that the
    racial bias alleged by Peters would also produce findings that East
    Asians have relatively larger brains than do Europeans.

    Allometric and nutritional factors

    Peters (1993) misstates when and why it is appropriate to correct for
    variation in body size (e.g., height or weight) when analyzing human
    attributes. It is only appropriate to correct for body size if one
    wishes to determine whether two (or more) individuals or groups are
    relatively different in some attribute, when it is already known that
    they are absolutely different in that attribute and/or in body size.
    For example, men and women differ in both absolute brain size and
    absolute body size. Thus, it is appropriate to correct for body size
    to determine if men have relatively larger brains. But, it would be
    inappropriate to correct for body size to determine if men have
    absolutely higher IQs.

    Consider this simple analogy: John Doe is 178 cm tall and can jump 1 m
    off the ground, whereas basketball star Michael Jordan is 208 cm tall
    and can jump 1.17 m off the ground. There are two questions that we
    can ask from this: (1) For his size, can Michael Jordan jump higher?
    (Answer is no he's 17% taller and can jump 17% higher), and (2) Can
    Michael Jordan jump higher? (Answer is, obviously, yes).

    Now, consider Peters' argument that to determine if larger brains
    produce (absolutely) higher IQs, one must correct for body size. This,
    as can be seen from the above, makes no sense. A higher IQ is a higher
    IQ (just as a higher jump is a higher jump) regardless of body size.
    On average, taller people have higher IQ's, not because they are
    taller, per se, but because, on average, they have larger brains.
    Correcting for body size reduces the question to a nullity, i.e., do
    tall people with their larger brains have relatively higher IQ's?

    Peters erred similarly when he argued that age must be controlled when
    analyzing brain-size/IQ relations in adults. Both brain size (Ho et
    al., 1980) and IQ (Brody, 1992) decline after the age of 45 years.
    This likely is not coincidental but, regardless, if one corrects for
    age then the result would simply be that brains of similar size tend
    to produce similar IQ's.

    Peters' erroneously stated that subjects in studies of brain-size/IQ
    relations should have similar early-life nutrition and be from the
    same social class. His rationale is that these factors can affect
    brain size. But, the question is do people with smaller brains have
    lower IQ's? , not why do they have smaller brains? . It might be
    interesting to know why John Doe is shorter than Michael Jordan but,
    regardless, he cannot jump as high.

    Brain size and intelligence

    As Lynn (1993) showed, the IQ/brain-size relation is ubIQuitous.
    Studies, additional to those provided by Lynn (1993), show that the
    correlation ranges from 0.10 to 0.30 with a mean of about 0.20
    (Wickett, Vernon, & Lee, 1994). The head-perimeter/IQ relation occurs
    in Orientals as well as whites and blacks and is apparent early in
    life. The National Collaborative Perinatal Project (Broman et al.,
    1987) found that head perimeter at birth, at 1 year, and at 4 years
    correlated with IQ at age 7 from r = 0.13 to 0.24 in 19,000 black and
    17,000 white children. Jensen and Johnson (1994) used these data to
    show that head size at age 7 (although not at age 4) is correlated
    with IQ within-families (i.e., among same-sex full siblings, with age
    partialed out), thus indicating a functional relation between brain
    size and IQ.

    Magnetic resonance imaging technIQues that create a 3-dimensional
    model of the brain in vivo confirm the brain-size/IQ relation. Five
    studies found an average correlation greater than 0.40, an improvement
    over studies that used head perimeter as a measure (Willerman et al.,
    1991; Andreasen et al., 1993; Raz et al., 1993; Egan et al., 1994;
    Wickett et al., 1994). Peters critIQued the two studies then
    available, but only confused the issue. First, he claimed that
    Willerman et al.'s (1991) low IQ group, because it averaged only 90.5,
    was an improper control . It was, however, not intended to be a
    control. Importantly, Willerman et al. showed that those with below
    average IQ had, on average, smaller brains. Second, Peters (1993)
    almost conceded the brain-size/IQ relation in his footnote citation to
    Andreasen et al. (1993). However, even there he suspected bias, i.e.,
    self-selection of subjects. But, this could only bias such results if
    people with large-brains/high-IQ and small-brains/low-IQ volunteered,
    whereas those with large-brains/low-IQ and small- brains/high-IQ did
    not. We are unaware of evidence to support such an implausibility.
    Regardless, beside studies by Willerman et al. (1991) and Andreasen et
    al. (1993) cited by Peters (1993), the brain-size/IQ relation
    established using magnetic resonance imaging was corroborated by Raz
    et al. (1993), Egan et al. (1994), and Wickett et al. (1994).

    The null hypothesis of no relation between brain size and IQ is false.
    In anticipation of this, Peters (1993) argued that even if
    brain-size/IQ correlations are valid, they account for only a small
    percentage of variation. But, it is predictable that correlations
    between IQ and overall brain size will be modest. First, much of the
    brain is not involved in producing what we call intelligence; thus,
    variation in size/mass of that tissue will reduce the correlation.
    Second, IQ is an imperfect measure of intelligence and thus, variation
    in IQ scores is an imperfect measure of variation in intelligence.

    Sex differences

    Peters (1993) correctly noted the absolute male/female difference in
    brain size. He was, however, incorrect that comparisons of brain size
    across sex cannot be made because there are (supposedly) no
    appropriate scalars of body size. Ankney (1992) reexamined Ho et al.'s
    (1980) autopsy data on 1,261 Americans aged 25 to 80 after excluding
    obviously damaged brains. Using allometric technIQues that are
    standard in comparative biology, Ankney (1992) found that at any given
    surface area or height, brains of European-American men are heavier
    than those of European-American women and brains of African-American
    men are heavier than those of African-American women. For example,
    among 168 cm (5'7 ) tall European-Americans (the approximate overall
    mean height for men and women combined), brain mass of men averages
    about 100 grams heavier than that of women.

    Ankney's (1992) results were confirmed in Rushton's (1992) study of a
    stratified random sample of U.S. Army personnel. After adjusting for
    effects of age, stature, weight, military rank and race, cranial
    capacity of men averaged 1,442 cm3 and women 1,332 cm3. This
    difference was found in all of the many analyses that were done to
    control for various possible body size effects (see Rushton, 1992).
    Moreover, the difference was replicated across samples of
    Asian-Americans, European-Americans and African-Americans, as well as
    in officers and enlisted personnel.

    Peters (1993) correctly noted the paradox that women have
    proportionately smaller brains than do men, but apparently have the
    same IQ scores. Thus, Ankney (1992) proposed that the sex difference
    in brain size relates to those intellectual abilities at which men
    excel. Briefly, according to Kimura (1992), women excel in verbal
    ability, perceptual speed, and motor coordination within personal
    space; men do better on various spatial tests and on tests of
    mathematical reasoning. Ankney hypothesized that it may require more
    brain tissue to process spatial information. Just as increasing word
    processing power in a computer may require extra capacity, increasing
    3-dimensional processing, as in graphics, requires a major jump in
    capacity. In support of Ankney's hypothesis, although Lynn (1994)
    found that men average 4 points higher than do women on standard IQ
    tests, Ankney (1995) showed that nearly all of this difference derived
    from men's higher scores on spatial and mathematical reasoning
    subtests.

    Race differences

    Rushton (1995) reviewed 100 years of scientific literature and found
    that across a triangulation of procedures, brains of East-Asians and
    their descendants average about 17 cm3 (1 in3) larger than those of
    Europeans and their descendents whose brains average about 80 cm3 (5
    in3) larger than those of Africans and their descendents. Although
    critics can pick outliers to show counter-examples and suggest
    opposite trends (as could critics of a statement that men are, on
    average, taller than women) the aggregated data are clear (see
    Rushton, 1995, for full discussion of alleged counter examples).

    Consider the following statistically significant comparisons. Using
    brain mass at autopsy, Ho et al. (1980) summarized data for 1,261
    adults (see above) and reported a sex-combined difference between 811
    European- Americans with a mean of 1,323 g (sd = 146) and 450
    African-Americans with a mean of 1,223 g (sd = 144). Using endocranial
    volume, Beals et al. (1984, page 307, Table 5) analyzed 20,000 crania
    and found sex-combined brain cases differed by continental area.
    Excluding Caucasoid areas of Asia (e.g., India) and Africa (e.g.,
    Egypt), 19 East Asian populations averaged 1,415 cm3 (sd = 51), 10
    European groups averaged 1,362 cm3 (sd = 35) and 9 African groups
    averaged 1,268 cm3 (sd = 85). Using external head measure- ments,
    Rushton (1992) found, in a stratified random sample of 6,325 U.S. Army
    personnel, measured in 1988 to determine head size for fitting
    helmets, Asian-Americans, European-Americans, and African-Americans
    averaged 1,416, 1,380, and 1,359 cm3, respectively (see also, Rushton,
    1994).

    Globally, racial differences in brain size parallel those found in
    measured intelligence. Europeans in North America, Europe and
    Australasia have mean IQs of around 100. For East Asians, measured in
    North America and in Pacific Rim countries, means range from 101 to
    111. Africans living south of the Sahara, African-Americans and
    African-Caribbeans (including those living in Britain), have mean IQs
    of from 70 to 90 (Lynn, 1991). Elementary speed of information
    processing in 9- to 12-year-olds, in which children decide which of
    several lights stands out from others, show that racial differences in
    mental ability are pervasive. All children can perform the tasks in
    less than 1 s, but more intelligent children, as measured by
    traditional IQ tests, perform the tasks faster than do less
    intelligent children. Japanese and Hong Kong children have faster
    decision times (controlling for movement time) than do British and
    Irish children who have faster decision time than South African Black
    and African-American children (Jensen, 1993; Jensen & Whang, 1993;
    Lynn, 1991).

    Evolutionary considerations

    Metabolically, the human brain is an expensive organ. Representing
    only 2% of body mass, the brain uses about 5% of basal metabolic rate
    in rats, cats, and dogs, about 10% in rhesus monkeys and other
    primates, and about 20% in humans. Thus, from an adaptationist
    perspective, unless large brains substantially contributed to
    evolutionary fitness (defined as increased survival of genes through
    successive generations), they would not have evolved.

    Paradoxically, Peters (1993) cited Haug (1987) to refute speculations
    about the significance of differences in brain size across
    individuals, sex, or race , even though Haug (1987, p.135) reported a
    correlation of r = 0.479 (n = 81, p < .001) between number of cortical
    neurons and brain size including both men and women in the sample.
    Haug's analysis showed that a person with a brain size of 1,400 cm3
    has, on average, 600 million fewer cortical neurons than an individual
    with a brain size of 1,500 cm3. The difference between the low end of
    normal (1,000 cm3) and the high end (1,700 cm3) equates to 4.200
    billion neurons (a difference of 27% more neurons for a 41% increase
    in brain size).

    Haug noted that most female data points lay above the regression line
    (i.e., women average more neurons for a given brain size than do men).
    This suggests that women's brains are differently organized than are
    men's, and so causes and results of race differences in brain size may
    be different from those of sex differences. Kolakowski and Malina
    (1974) hypothesized that differing roles of men and women during human
    evolution produced a sexual dichotomy in abilities. Men roamed from
    the home base to hunt, which would select for targeting ability and
    navigational skills; women were relatively sedentary. Ankney (1992,
    1995) expanded on this hypothesis to argue that selection for such
    abilities also selected for relatively larger brains in men and that
    it may require more brain tissue to process spatial information.

    Rushton (1995) provided an evolutionary hypothesis for why East Asians
    have the largest brains. The currently accepted view of human origins
    posits a beginning in Africa some 200,000 years ago, an
    African/non-African split about 110,000 years ago, and a European/East
    Asian split about 40,000 years ago (Stringer & Andrews, 1988).
    Evolutionary selection pressures were different in the hot savanna
    where Africans evolved than in the cold arctic where East Asians
    evolved. According to Rushton (1995), the further north the
    populations migrated, out of Africa, the more they encountered
    cognitively demanding problems of gathering and storing food, gaining
    shelter, making clothes, and raising children during prolonged
    winters. As the original African populations evolved into Europeans
    and East Asians, they did so in the direction of larger brains,
    greater intelligence, slower rates of maturation, and other traits
    that differentiate these populations.

    Conclusion

    The evidence is overwhelming that there are racial and sexual
    differences in brain size, that there are racial differences in
    general IQ, that there are sexual differences in verbal versus
    performance IQ, and that differences in mental abilities are related
    to differences in brain size. Peters cannot simply deny this evidence.
    Thus, important research questions include (1) what is responsible for
    the group differences, i.e., are they genetically and/or
    environmentally caused?, (2) does the brain size/IQ correlation
    indicate cause and effect ?, and (3) is there bidirectional causality
    such that the greater learning ability of high IQ children feeds back
    to produce even larger brain size?

    ----------------------------------------------------------------------

    References

    Andreasen, N.C., Flaum, M., Swayze, V., O'Leary, D.S., Alliger, R.,
    Cohen, G., Ehrhardt, J. & Yuh, W.T.C. (1993). Intelligence and brain
    structure in normal individuals. American Journal of Psychiatry, 150,
    130-134.

    Ankney, C.D. (1992). Sex differences in relative brain size: The
    mismeasure of woman, too? Intelligence, 16, 329-336.

    Ankney, C.D. (1995). Sex differences in brain size and mental
    abilities: Comments on R. Lynn and D. Kimura. Personality and
    Individual Differences, 18, 423-424.

    Beals, K.L., Smith, C.L. & Dodd, S.M. (1984). Brain size, cranial
    morphology, climate, and time machines. Current Anthropology, 25,
    301-330.

    Brody, N. (1992). Intelligence. New York: Academic Press.

    Broman, S.H., Nichols, P.L., Shaughnessy, P. & Kennedy, W. (1987).
    Retardation in young children. Hillsdale, NJ: Erlbaum.

    Egan, V., Chiswick, A., Santosh, C., Naidu, K., Rimmington, J.E., &
    Best, J.J.K. (1994). Size isn't everything: A study of brain volume,
    intelligence and auditory evoked potentials.Personality and Individual
    Differences, 17, 357-367.

    Haug, H. (1987). Brain sizes, surfaces, and neuronal sizes of the
    cortex cerebri. American Journal of Anatomy, 180, 126-142.

    Ho, K.C., Roessmann, U., Straumfjord, J.V., & Monroe, G. (1980).
    Analysis of brain weight. Archives of Pathology and Laboratory
    Medicine, 104, 635-645.

    Jensen, A.R. (1993). Spearman's hypothesis tested with chronometric
    information processing tasks.Intelligence, 17, 47-77.

    Jensen, A.R., & Johnson, F.W. (1994). Race and sex differences in head
    size and IQ.Intelligence, 18, 309-333.

    Jensen, A.R., & Whang, P.A. (1993). Reaction times and
    intelligence.Journal of Biosocial Science, 25, 397-410.

    Kimura, D. (1992). Sex differences in the brain.Scientific American,
    267 (No. 3), 119-125.

    Kolakowski, D., & Malina, R.M. (1974). Spatial ability, throwing
    accuracy, and man's hunting heritage.Nature, 251, 410-412.

    Lynn, R. (1991). Race differences in intelligence. Mankind Quarterly,
    31, 255-296.

    Lynn, R. (1993). Brain size and intelligence in man: A correction to
    Peters. Canadian Journal of Experimental Psychology, 47, 748-750.

    Lynn, R. (1994). Sex differences in intelligence and brain size.
    Personality and Individual Differences, 17, 257-271.

    Peters, M. (1993). Still no convincing evidence of a relation between
    brain size and intelligence in humans. Canadian Journal of
    Experimental Psychology, 47, 751-756.

    Raz, N., Torres, I.J., Spencer, W.D., Millman, D., Baertschi, J.C., &
    Sarpel, G. (1993). Neuroanatomical correlates of age-sensitive and
    age-invariant cognitive abilities. Intelligence, 17, 407-422.

    Rushton, J.P. (1992). Cranial capacity related to sex, rank, and race
    in a stratified random sample of 6,325 U.S. military personnel.
    Intelligence, 16, 401-413.

    Rushton, J.P. (1994). Sex and race differences in cranial capacity
    from International Labour Office data. Intelligence, 19, 281-294.

    Rushton, J.P. (1995). Race, evolution, and behavior. A life-history
    perspective. New Brunswick, NJ: Transaction.

    Stringer, C.B. & Andrews, P. (1988). Genetic and fossil evidence for
    the origin of modern humans. Science, 239, 1263-1268.

    Wickett, J.C., Vernon, P.A., & Lee, D.H. (1994). In vivo brain size,
    head perimeter, and intelligence in a sample of healthy adult females.
    Personality and Individual Differences, 16, 831-838.

    Willerman, L., Schultz, R., Rutledge, J.N., & Bigler, E.D. (1991). In
    vivo brain size and intelligence. Intelligence, 15, 223-228.

    Canadian Journal of Experimental Psychology (Vol. 49, No. 4)

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    Post Re: Does Brain size matter?

    It was once said that betwen species, brain size mattered but within a species, it did not. This, of course, was the Franz Boas, American anthropological dogma. Now we have Out of Africa and the question arises if we are not really two species, Africans and non-Africans. This throws the old dogma back on its face.

    Whites have bigger heads than Blacks. But Blacks have bodies as large or perhaps heavier than Whites. This means allometry comes into play. Allometry was not mentioned as being controlled in the Black-White comparison stated above. This may be a fault in the study. Also, I.Q. differences between American Whites and Blacks become even greater if we consider, for instance, German Whites as the article did. These I.Q. differences were not mentioned, only cranial capacities of various "white" groups as if they were all the same.

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    Post Re: Does Brain size matter?

    If I recall correctly, the Neanderthals had the biggest brains.
    The Phora

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    Post Re: Does Brain size matter?

    Quote Originally Posted by FadeTheButcher
    If I recall correctly, the Neanderthals had the biggest brains.
    True, but just compared to the human average. There are many especially Europid and Mongolid people which got bigger brains.

    But its not just size but also structure which is even more important for intelligence, especially the Gyri (whorls in English?) of the Neocortex.
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    Post Re: Does Brain size matter?

    Quote Originally Posted by Agrippa
    True, but just compared to the human average. There are many especially Europid and Mongolid people which got bigger brains.

    But its not just size but also structure which is even more important for intelligence, especially the Gyri (whorls in English?) of the Neocortex.
    I second that, it is not size, it is the number of folds that increases brain capacity. Great post!

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    Post Re: Does Brain size matter?

    Quote Originally Posted by Razmig
    I second that, it is not size, it is the number of folds that increases brain capacity. Great post!
    Thx, but I didnt want to say that brain size doesnt matter (in fact I dont really know but think it matters), but is there are other, maybe even more important factors.
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    Post Re: Does Brain size matter?

    Quote Originally Posted by Agrippa
    Thx, but I didnt want to say that brain size doesnt matter (in fact I dont really know but think it matters), but is there are other, maybe even more important factors.
    Dolphins and some whales have fairly large brains. The density of the brain and its folds is what makes human brains so complex. Also the size of the animal is supposed to have something to do with its brain mass (in Mammals). I think (it's been a long time) I remember in my first anat class that the horse brain is the most similar to a humans (In size), but a monkeys similar in complexity. All humans have the same brain (with different neural stem cell variants).

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