Human Mental Abilities
Lecture 6
Leonardo Gabales
1
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
2
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
3
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
4
it is defined by several indicators (like IQ)
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
5
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
6
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
7
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
8

But remember, the correlation between
SES and IQ isn’t 1.0…
9
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
10
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
11
“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)
12
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
13
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
14
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
15
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
16
the environmental position
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 (?!)
17
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
18
they don’t understand the questions
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
19
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
20
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
21
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
22
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
23
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
24
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
25
individualist mainstream culture
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
26
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
27
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
28
weekly earnings
Gender Earnings Ratio
29
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
30
Gender Differences in TE scores
Changes in average Tertiary Entrance Scores (HSC) for boys & girls
between 1981 & 1996
31
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
32
“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)
33
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
34
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
35
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
36
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
37
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
38
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
39
Girls Just Want to Have Sums
40
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
41
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
42
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
43
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
44
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 highperforming groups AND among low-achieving groups
Male mean
Female mean
Test Score
45
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
46
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
47
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
48
Summary

Group differences in intelligence…

SES


Race differences


an advantage (on average) in test scores for those with higher
SES
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
49