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Human Mental Abilities

Lecture 6

Leonardo Gabales

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Group Differences in Intelligence

Group differences considered here:

Socio-economic status

Race/ethnicity

Gender

Why are individual differences psychologists interested in group differences?

Mainly because of the social effects of the misuse (& abuse?) of intelligence test scores

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Test Bias Bias refers to a test showing differences when no real

differences exist

Establishing the presence of bias requires a criterion against which the test can be validated:

E.g., If it is known that blacks & whites perform equally well at a particular job, but a test used to select personnel for that job indicates significant black/white differences - then the test is said to be biased

However, if test score differences correspond to criterion differences - the test cannot be said to be biased

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Group Differences: SES Socio-Economic Status (SES) differences

SES is defined by several indicators Occupation Income Residence Education

Often related to “social class”

Considered a latent variable - in the sense that it is defined by several indicators (like IQ)

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Group Differences: SES

Correlation between SES & IQ is between .5 - .7

This relationship between SES & IQ might be interpreted in 2 ways:

Tests of intelligence are biased in favour of middle-class white Anglo-Saxon groups – such groups & their social values, dominate upper strata of SES

OR

Tests are valid measures of a socially-important construct

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Occupational Selection Bias Occupational selection bias has been

examined carefully during the past two decades & many jobs & tests have been scrutinised

The issue was tested in a series of court cases in the USA contesting the employment decisions based on intelligence test scores:

Many challenged ‘positive discrimination’ whereby people with higher test scores were passed over in favour of members of culturally disadvantaged groups

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Occupational Selection Bias

It became accepted that each selection test should have a proven validity for a particular job

This had practical consequences:

It was thought that tests of general intelligence should be replaced by tests of specific abilities that may have higher validity for particular jobs

Faced with increased costs of research & administration, many corporations abandoned the use of tests altogether

This course of action appears poorly justified

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SES & IQ: Concluding Remarks

Tests of intelligence appear to correlate with SES because they are valid measures of a socially important construct

Differences between various occupational status categories seem to be real & intelligence tests appear to be sensitive to these effects

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But remember, the correlation between SES and IQ isn’t 1.0…

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Group Differences: Race & Ethnicity

Race: a population of people who share a common pool of genes that differ from those of other races

This often leads to characteristic physical attributes (e.g., skin colour, height, blood-group) which are used to identify a race

Ethnic group: a society consisting of people who share the same customs, culture, traditions, language, religion, etc.

Often, these people constitute a single nation or tribe; they might tend to interbreed- thus sharing a common gene pool - but this is not a necessary condition as it is with race

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Group Differences: Race & Ethnicity

The largest number of studies of racial differences has been carried out in the USA - comparing performance of blacks & whites

A well-established finding is that, on the average, US blacks perform about 1 SD below US whites on intelligence tests

This means that, on IQ tests that have a mean of 100 & standard deviation of 15, the average performance for African-Americans is about 85

It is interesting, however, that in infancy (until the age of 4) black children show superiority over whites on sensory motor tasks that are used as early measures of intelligence

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“All our social policies are based on the fact that their intelligence is the same as ours whereas all the testing says not really”

(James Watson, speaking about Africa)

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Group Differences: Race & Ethnicity

Another racial comparison that has recently become ‘fashionable’ is Whites vs Asians:

Asians tend to score 3 to 5 IQ points better overall, show superior non-verbal & quantitative abilities, & have somewhat inferior verbal abilities

This is usually attributed to high values placed on achievement & education in Asian societies

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Debate: Racial & Ethnic Differences There has been considerable debate on the

causes of these racial differences:

Some extreme Darwinist claims have been made:

e.g., African-Americans are less intelligent than whites because slaves brought from Africa were less intelligent than their peers who evaded capture

The truth is… we do not really know what causes (or how to reduce) racial differences

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Debate: Racial & Ethnic Differences

There are probably many different factors involved…

Debate has focused on the role of environmental & genetic factors in causing race differences in intelligence

Jensen & Eysenck used a ‘plausibility argument’ in support of genetic causation:

Because genetic determination of within-group differences has been well established, it is plausible that between-group differences are similarly determined

Jensen ultimately abandoned this argument

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Environmental Factors (?) Evidence from empirical studies has also been

considered:

African-Americans living in the northern USA tend to obtain higher scores than those living in the south

Importantly the North has a higher standard of living & better educational system

This is also true for urban vs rural comparisons

These results have generally been used as evidence for the environmental position

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Selective Movement

HOWEVER … group differences in test scores may also be attributed to selective movement

i.e., movement of more intelligent populations away from impoverished environments

Does this salvage the genetic argument (?!)

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Cultural Bias Cultural bias is important – particularly

regarding racial differences

It is argued that apparent racial differences stem from tests assuming dominant culture values that are foreign to minority subcultures (e.g., Afro-Americans, especially the poor)

Thus members of minority groups might score poorly, not because they are less able, but simply because they don’t understand the questions

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Cultural Bias: Example

This accusation has been tested in a study comparing performance on a culturally sensitive verbal intelligence test for 3 different cultural groups - British, African-American & US whites

As expected, African-Americans tended to score lower than US Whites

Also, British were closer in test scores to US Whites than to African-Americans

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Cultural Bias: Results

The most important evidence for cultural differences, however, was found in the patterns of item difficulty:

Items that were difficult for African-Americans were also difficult for US Whites

Other items were difficult for both US groups, but were not difficult for British, & vice versa

Cultural differences between US blacks & whites appear to be smaller than cultural differences between the Americans & the British

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Cultural Bias: Conclusions

Generally, if some items are more difficult for one group than they are for another group, & if the situation is reversed for other items, there is evidence of cultural bias

In the above study, this was true for American groups vs. British, but not for African-Americans vs US Whites

Within Group Differences (i.e., Americans) were small – BUT – Between Group Differences (i.e., African-Americans + US Whites vs British) were much larger

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Cultural Deprivation Advocates of environmental causation for race

differences often introduce the concept of cultural deprivation

This claim is difficult to investigate & there is some disconfirmatory findings:

Native Americans & those of Spanish descent tend to score higher than African-Americans, yet their environmental & cultural handicaps are also serious

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Radical Cultural Relativism Hypothesis

The precise meaning of cultural differences & their implications for intelligence are not well understood

The radical cultural relativism hypothesis proposes that there are no (cross culturally) universal cognitive processes

Thus: descriptions & assessments of cognitive capacity must be culturally valid - i.e., sensitive to the cultural context in which they are applied

Cross-cultural comparisons would therefore be impossible

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Radical Cultural Relativism Hypothesis

Less radical positions allow for comparisons when cultural differences are taken into account

In contrast, other positions allow for the possibility that psychological universals exist

Comparison between racial or ethnic groups using traditional intelligence tests are valid

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Studies of Australian Aboriginals Have traditionally reported low (often 1 SD+ lower than

‘average’) levels of intelligence- but many studies are dated (pre-WWII)

Recent anthropological studies suggest that aspects of Aboriginal culture seem to emphasise abilities that may be poorly sampled by the typical intelligence tests

E.g., abilities associated with reasoning based on spatial relationships – which are of cultural significance to Australian Aborigines

It has also been argued that Aboriginal cultures emphasise collectivist values

This might impair children’s ability to develop abilities fully within the individualist mainstream culture

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Studies of Australian Aboriginals

One study has shown that on a particular test involving memory for spatial relationships (rural) Aboriginal children outperform white Australians

Children were tested for recall of locations of objects within a matrix, with the response being to actually position the objects correctly within the matrix

Results indicated that Aboriginal children used visual encoding strategies that were superior to the white children’s verbal rehearsal strategies

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Group Differences: Gender

There are many differences (i.e., inequalities) between males & females within our society

HOWEVER: substantial changes have taken place over the past half-century

Some differences that were considered to be innate & therefore unchangeable are obviously not so

It is hard to say how many of these differences will disappear in a near future - overall, it appears that females are still disadvantaged in our society

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Gender & Earnings Significant differences exist in earnings between

males & females in our society

In 1969, women in full-time employment earned about 58% of men’s average weekly earnings

By 1973, the figure had improved to 73%

In 1994, the figure had further improved to 80%

In 2007, women earned about 90% of men’s average weekly earnings

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Gender Earnings Ratio

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Gender & Scholastic Achievement

It has been claimed that over recent years boys have become the weaker sex in education - perhaps as a result of all the changes that have taken place in girls' education

Prior to the 1980s boys (on average) outperformed girls in the HSC – this difference between genders was minimal by 1980-81

By 1993 girls (on average) outperformed boys in the HSC by more than 12 marks - girls also outperformed boys in five of the eight key learning areas, by 1996 this difference was almost 20 marks

For all subjects, a higher proportion of boys tended to cluster at the bottom of the mark range

At the top of HSC scores there are still more boys than girls but the difference has diminished considerably over the past 5 years

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Gender Differences in TE scores

Changes in average Tertiary Entrance Scores (HSC) for boys & girls between 1981 & 1996

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Gender & Scholastic Achievement

15 years ago, only one-third of the top 1000 students were girls - today the ratio is closer to being 60-40 in favour of girls

Full circle? - new programs have been suggested to redress the differences between boys & girls!

BUT: do these trends reflect true differences in ability?

There is a large body of literature that compares males & females with respect to their performances on cognitive tests

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“The chief distinction in the intellectual powers of the two sexes is shewn by man's attaining to a higher eminence, in whatever he takes up, than can woman - whether requiring deep thought, reason, or imagination, or merely the use of the senses and hands”

(Charles Darwin)

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Gender & Cognitive Ability Earlier studies tend to report large differences

E.g., girls were found to have superior verbal ability, particularly verbal fluency - boys tended to score high on mechanical tasks

There have been several lines of explanations of gender differences:

Cultural & social factors were seen as being particularly important - girls do not have equal opportunity after school

There are personality differences - docility & submissiveness in girls - restlessness & greater physical activity of boys lead to different lifestyles & career paths

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Gender & Cognitive Ability

Boys & girls mature at different rates (girls mature about two years earlier than boys) which may cause differences in achievement

Neuropsychological differences – there exist differences in brain structures (e.g., the hypothalamus) & in cerebral lateralization in males & females

Hormonal differences especially in androgen/estrogen ratio may be related to (some) cognitive abilities

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Gender & Cognitive Ability

However… gender differences in cognitive ability are changing – the differences between males & females tend to diminish with successive generations

“Gender differences are small and disappearing …”

The following data clearly demonstrates changes across time in differences in actual performance on psychological tests

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Male-Female Differences in IQ Units

1947 1962 1972 1980

Spelling -8.10 -7.95 -7.05 -6.75

Language -7.35 -6.15 -6.00 -6.00

Clerical -9.30 -7.95 -6.60 -5.10

Mech. Reasoning 19.95 15.00 12.45 11.40

Spatial Relations 5.55 3.90 2.85 2.25

Verbal Relations 2.10 .90 .15 -.30

Abstract Reasoning 3.45 1.35 .30 -.60

Num Reasoning 3.15 1.50 -.15 -1.50

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Gender & Cognitive Ability For many abilities - e. g., Verbal Reasoning, Abstract

Reasoning, Numerical Reasoning - these differences are not significant

The only difference in this Table that remains significant to this day is for Mechanical Reasoning - males are clearly superior to females in dealing with mechanical & spatial problems

It seems likely that this difference will remain significant in the future

However, in our work with the Gf/Gc test battery, we have repeatedly found no overall gender differences in intelligence

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Gender & Cognitive Ability This general trend of decline in gender

differences argues against biological explanations & implicates changes in our culture

Factors such as sexual stereotyping of different activities, interests, & curricular choices among high school students may be important factors

The only exception to this general conclusion is spatial/mechanical abilities…

Gender differences in these abilities cannot be accounted for by explanations in terms of cultural factors

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Girls Just Want to Have Sums

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Gender Differences in Spatial Ability Biological explanations of differences in spatial ability are

in terms of:

Sex-linked gene for spatial ability

Differences in the degree of cerebral lateralization - males are more lateralized than females

it is assumed that the right cerebral hemisphere which is responsible for performance on spatial tasks is more specialized in males than in females - females are said to use a more ‘integrated’ mode of thinking than males

Hormonal differences, especially androgen/estrogen ratio.

At this stage, it is not clear which one of these three explanations is the most adequate - they may all be closely related

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Gender & Cognitive Ability

While the overall differences in cognitive abilities seem to have disappeared, two findings regarding gender differences have gained in prominence:

1st FINDING: significant gender differences on some types of tasks exist in samples that are above average in ‘general ability’

Even though overall mean difference between males & females in numerical & mathematical tasks is small, there are a disproportionate number of males who show high mathematical ability

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Gender & Cognitive Ability

2 main explanations have been offered:

Mathematical ability may be dependent on spatial/mechanical abilities & since males are superior on these latter types of abilities, they tend to obtain higher scores on tests of mathematical ability

Small differences in central tendency may imply large differences at the extremes of the distribution - there will be a disproportionately large number of males with high scores

i.e., This difference is due to statistical properties of the distribution of scores, not to a manipulation of social conditions in favor of males

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Gender & Cognitive Ability

2nd FINDING: there are significant differences in variability between males & females - there is a greater variability among males than among the females in many psychological traits

There are more males in jails, in psychiatric institutions, etc.

At the same time, there is a large proportion of males than females among the high achieving members of our society

Overall, in many personality traits, the range of scores for males is greater than the range of scores for females

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Gender & Cognitive Ability Several recent large-scale studies indicate that variance of males on

general intelligence tests is about 10% larger than variance of females

Thus, even though arithmetic means for these two groups do not differ significantly, the spread of scores is clearly different

As a consequence, one finds more males than females among both high-performing groups AND among low-achieving groups

Male mean Female mean

Test Score

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Stereotype Threat People from disadvantaged groups (e.g.

ethnic minorities and women) may worry about conforming to negative stereotypes May view testing as less important

because “they’ll just be bad at it anyway” Heightened test anxiety

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Stereotype Threat When exposed to stereotype threat, blacks

often do worse than whites on problem solving Remove the stereotype and the differences often

vanish Women often do worse in mathematics when

exposed to stereotype threat This difference generally vanishes when the

stereotype threat is removed At least one study has shown that women are

actually better than men at mathematics once the stereotype threat is removed

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Stereotype Threat White males aren’t immune either

White male engineering students did worse in mathematics when told that they were participating in research to determine why Asians were better at mathematics

Asian females and mathematics When their gender was made salient they did

worse But when their ethnicity was made salient they did

better

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Summary Group differences in intelligence…

SES an advantage (on average) in test scores for those with higher

SES

Race differences significant advantages (overall) for US Whites over US Blacks,

US Asians over US Whites (although difference is modest), & Australian Whites over Australian Aboriginals

Gender differences Overall, are small & disappearing – an advantage for females in

some domains of verbal abilities, & for males in spatial/mechanical abilities