User:Wdhamilton/1

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Many studies report that IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[1] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[2] The correlation was also found in some studies to hold true within families (where environmental factors can be considered to be similar),^[3] but in one study of 36 sibling pairs essentially zero correlation between brain size and IQ was found when comparing within families.^[4] Some studies have found racial differences in brain size.^[5]

Others interpret these studies as having found no racially-based difference, arguing instead the the variation should be described in terms of geography.^[6] Perhaps the largest single study, by Beals et al. 1984 which analyzed more than 20,000 skulls from 122 ethnically distinguishable populations, found that brain size varied with distance from the equator (r=.62). Lieberman 2001 explains "...the relationship between latitude and cranial size is an example of Bergmann's principle that crania are more spherical in cold climates because mass increases relative to surface area to conserve core temperatures...Beals, Smith, and Dodd emphasize that this relationship is independent of "race."".^[7] The biogeographical variation in brain size is widely described as an evolutionary adaptation to climate. Building on the findings of Beals et al., Templer and Arikawa 2006 reported that mean national IQ is correlated with skin color and climate.

Cranial vault size and shape have changed greatly during the last 150 years in the US.^{[citation needed]} These changes must occur by early childhood because of the early development of the vault.^{[citation needed]} The explanation for these changes may be related to the Flynn effect.^[8]

A meta-analysis found that reaction times correlates with IQ by about .30 to .50.^[9] Average racial differences have been found on tests of response time.^[10] Reaction time also correlates with brain volume at approximately .4.^[11]

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There are several hotly debated studies which have concluded that there are race-based differences in brain size. These studies are criticized as having found no genetically racially-based difference, with critics arguing instead the the variation correlates much better in terms of geography and environment.^[12][13] Perhaps the largest single study, by Beals et al. 1984 which analyzed more than 20,00 skulls from around the world, found that brain size varied with latitude of biogeographic ancestry. Lieberman (2001) explains "...the relationship between latitude and cranial size is an example of Bergmann’s principle that crania are more spherical in cold climates because mass increases relative to surface area to conserve core temperatures...Beals, Smith, and Dodd emphasize that this relationship is independent of "race."".^[14] The biogeographical variation in brain size is widely described as an adaptation to climate.

Cranial vault size and shape have changed greatly during the last 150 years in the US.^{[citation needed]} These changes must occur by early childhood because of the early development of the vault.^{[citation needed]} The explanation for these changes may be related to the Flynn effect.^[15]

Several studies report that IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[1] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[16] The correlation was also found in some studies to hold true within families (where environmental factors can be considered to be similar),^[17] but in one study of 36 sibling pairs essentially zero correlation between brain size and IQ was found when comparing within families.^[18]

A meta-analysis found that reaction times correlates with IQ by about .30 to .50.^[19] Average racial differences have been found on tests of response time, although it is also argued that some of these differences can be explained by cultural phenomena.^[20]

It is argued by some scientists that the combination of these correlations, of race to brain size, of brain size to reaction time, and of reaction time to IQ establishes a correlation between race and IQ. This conclusion is strongly objected to by other scientists, both on the basis of the initial correlation asserted between race and brain size, and the progressively weak correlation as the studies are combined.^[13]

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Many studies report that IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[1] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[21] The correlation was also found in some studies to hold true within families (where environmental factors can be considered to be similar),^[22] but in one study of 36 sibling pairs essentially zero correlation between brain size and IQ was found when comparing within families.^[23] Some studies have found racial differences in brain size.^[24]

Others interpret these studies as having found no racially-based difference, arguing instead the the variation should be described in terms of geography.^[25] Perhaps the largest single study, by Beals et al. 1984 which analyzed more than 20,000 skulls from around the world, found that brain size varied with latitude of biogeographic ancestry (r=.62). Lieberman 2001 explains "...the relationship between latitude and cranial size is an example of Bergmann's principle that crania are more spherical in cold climates because mass increases relative to surface area to conserve core temperatures...Beals, Smith, and Dodd emphasize that this relationship is independent of "race."".^[26] The biogeographical variation in brain size is widely described as an evolutionary adaptation to climate.

Cranial vault size and shape have changed greatly during the last 150 years in the US. These changes must occur by early childhood because of the early development of the vault. The explanation for these changes may be related to the Flynn effect.^[27]

A meta-analysis found that reaction times correlates with IQ by about .30 to .50.^[28] Average racial differences have been found on tests of response time.^[29] Reaction time also correlates with brain volume at approximately .4.^[30]

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Many studies report that IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[1] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[31] The correlation was also found in some studies to hold true within families (where environmental factors can be considered to be similar),^[32] but in one study of 36 sibling pairs essentially zero correlation between brain size and IQ was found when comparing within families.^[33] Some studies have found racial differences in brain size,^[34] while others found no racially-based difference.^[35] Perhaps the largest single study, by Beals et al. 1984 which analyzed more than 20,00 skulls from around the world, found that brain size varied with latitude of biogeographic ancestry. Lieberman (2001) explains "...the relationship between latitude and cranial size is an example of Bergmann’s principle that crania are more spherical in cold climates because mass increases relative to surface area to conserve core temperatures...Beals, Smith, and Dodd emphasize that this relationship is independent of “race.”".^[36] The biogeographical variation in brain size is widely described as an adaptation to climate. Cranial vault size and shape have changed greatly during the last 150 years in the US. These changes must occur by early childhood because of the early development of the vault. The explanation for these changes may be related to the Flynn effect.^[37]

A meta-analysis found that reaction times correlates with IQ by about .30 to .50.^[38] Average racial differences have been found on tests of response time.^[39]

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Many studies report that IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[1] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[40] The correlation was also found in some studies to hold true within families (where environmental factors can be considered to be similar)^[41], but in one study of 36 sibling pairs essentially zero correlation between brain size and IQ was found when comparing within families.^[42] Some studies have found racial differences in brain size^[43]. A large study by Beals et al. 1984 found that the brain size of indigenous populations varied with latitude. Lieberman and others, who do not believe that human variation should be described in terms of races, argue that the clinal view of brain size variation is superior to a racial description.^[44]. The biogeographical variation in brain size is widely described as an adapatation to climate. Cranial vault size and shape have changed greatly during the last 150 years in the US. These changes must occur by early childhood because of the early development of the vault. The explanation for these changes may be related to the Flynn effect.^[45]

A meta-analysis found that reaction times correlates with IQ by about .30 to .50.^[46] Average racial differences have been found on tests of response time.^[47]

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Many studies report that IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[1] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[48] The correlation was also found in some studies to hold true within families (where environmental factors can be considered to be similar)^[49], but in one study of 36 sibling pairs essentially zero correlation between brain size and IQ was found when comparing within families.^[50] Some studies have found racial differences in brain size^[51]. A large study by Beals et al. 1984 found that the brain size varied with latitude, pointing out that the racial correlation was much lower than correlation with climate. ^[52]. The biogeographical variation in brain size is widely described as an adaptation to climate (Lieberman, 2001). Cranial vault size and shape have changed greatly during the last 150 years in the US. These changes must occur by early childhood because of the early development of the vault. The explanation for these changes may be related to the Flynn effect.^[53]

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IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[1] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[54] Reaction times correlate with IQ by about .30 to .50.^[55] Studies have shown racial differences in both brain size^[56] and tests of response time.^[57] Cranial vault size and shape have changed greatly during the last 150 years in the US. These changes must occur by early childhood because of the early development of the vault. The explanation for these changes may be related to the Flynn effect.^[58]