4PAHPDFF Psychology and the Individual Week 5
BSc Psychology Year 1 Applications and Issues in the Study of Intelligence
APPLICATIONS AND ISSUES IN THE
STUDY OF INTELLIGENCE
UNDERSTAND THE ‘FLYNN EFFECT’ AND DESCRIBE POSSIBLE
EXPLANATIONS.
THE FLYNN EFFECT
• The Flynn effect describes the continued year-on-year rise of average IQ test scores in most
industrialised societies throughout the 20th Century
o It is not necessarily that we are seeing an increase in intelligence itself, but that the
increase is in the ability for people to solve abstract problems
• When new IQ tests were established, scores would be compared between the old and new
versions to test the validity of the new test
o Flynn found that participants averaging 100 on a revised (1972) Wechsler Intelligence
Scale for Children, also averaged 108 on the Wechsler Intelligence Scale for Children
(1947/1948)
o Higher scores on the older test demonstrated that they were finding the older test
easier, setting higher standards for average IQ over time
• Between 1952 and 1982 the average IQ score of Dutch men increased by 20 points—
reflecting a 1 SD increase in IQ (Flynn, 1987)
• Flynn (1984) found that white Americans gained 14 IQ points between 1932 and 1978, an
average of .30 IQ points per year
o This average growth per year was then found from 14 countries (Flynn, 1987)
o The highest rises were found in the non-verbal tests (fluid intelligence), with an
average of a 15 IQ point increase per generation
o The lowest rises were in verbal tests (crystallised intelligence), with an average of 9
IQ point increase per generation
EXPLANATIONS FOR THE FLYNN EFFECT
• Flynn argued for environmental explanations of this effect, since the increases are too rapid
to be due to genetic changes
Length of Schooling
• People are now attending school for more years than older generations did (Flynn, 1998;
Neisser, 1998; Williams, 1998)
• Research found that length of schooling was an important predictor of scores on verbal IQ
tests, and more important than age
o Although this trend differs from Flynn’s data in which verbal tests have lower rises in
IQ scores than non-verbal tests
o Therefore, Flynn and Williams argue that this is not a good explanation for the secular
rise in IQ test scores through generations
1
,4PAHPDFF Psychology and the Individual Week 5
BSc Psychology Year 1 Applications and Issues in the Study of Intelligence
Test-Taking Sophistication
• We now promote a culture for taking tests, which may mean that we have more practice with
them and therefore, have become better at taking them
o Our educational system is changing since we are encouraging more abstract thinking
and teaching students how to learn
• Flynn (1998) and Williams (1998) argued that teaching is increasingly being geared to certain
kinds of achievement tests
o For example, ideas about spatial reasoning are new ideas that may not have been
recognised in the early twentieth century
• Therefore, knowledge of intelligence tests by those taking them, as well as parents and
schools, may be leading to the increases
o However, knowledge of IQ tests themselves is unlikely to explain the Flynn effect’s
emphasis on non-verbal rather than verbal aspects of intelligence
o Moreover, increased familiarity with IQ tests does not significantly increase IQ points
(children taking the test twice only gain five or six points; Williams)
Child-Rearing Practices
• Parents today are more interested in their children’s intellectual development, and may
therefore be doing more to develop it (Flynn, 1998; Williams, 1998)
o For example, Sesame Street was created to provide early mental stimulation to raise
children’s awareness and intelligence
Head Start
• The Head Start Programme, which aims to narrow the gap between disadvantaged children
and other children in vocabulary, numeracy, and writing skills
o However, although children attending the programme showed an initial increase of
IQ points, after 2-3 years, these are often lost and the increases don’t remain superior
to disadvantaged children not in the programme (Locurta, 1991; McKey et al., 1985)
• Therefore, early childhood experience and intellectual promotion in early childhood cannot
fully explain the Flynn effect
The Cultural and Technological Age
• The growth of visual media may have made us become more visually aware
o Children spend more time learning through visual media, rather than just learning in
a classroom setting
o Adults have become more used to processing complicated visual information
• This exposure to complex visual media has produced genuine increases in a significant form
of intelligence—visual analysis
• Greenfield (1998) and Schooler (1998) argue that this may explain the growth of fluid
intelligence, such as in the Raven’s Matrices which only rely on visual material
o However, little direct evidence exists for the visual analysis hypothesis
Nutrition and IQ
• Lynn (1990;1998) argues that nutrition and healthcare improvements are some of the main
causal factors of the Flynn effect
o Nutrition is linked to larger brain sizes, and malnutrition to poor brain development
o Moreover, with nutrition having direct impacts on height increases, this may also be
the case for the brain and its functioning (intelligence)
o However, it is hard to test this since studies today usually use WEIRD samples where
children are relatively well-nourished (including where the effect was observed)
2
, 4PAHPDFF Psychology and the Individual Week 5
BSc Psychology Year 1 Applications and Issues in the Study of Intelligence
• Oddy et al. (2004) found that stopping breast feeding early (<6 months) was associated with
reduced verbal intelligence
o Those who were fully breast fed scored 3-6 points higher on a vocabulary test than
those who were never breast fed
o However, Der et al. (2006) found that the mothers of these children scoring higher
were also more intelligent, and when this was controlled for, there was no significant
relationship between breast feeding and the child’s intelligence
• Qian et al. (2005) found that iodine (an important mineral for the main hormone produced by
the thyroid, aiding metabolism and proper growth) was also linked to mental ability
o Children who received iodine supplements in-utero and after birth scored 8.7 IQ
points higher than those who did not
o This rose to 12 IQ points on non-verbal measures (e.g. Raven’s Matrices) and 17.25
IQ points on non-verbal and verbal measures (e.g. Stanford-Binet)
• Benton and Roberts (1988), contrastingly found no difference in verbal intelligence scores
between those given vitamin and mineral supplements and those not
o However, non-verbal intelligence did increase for those who had the supplements
from 111 to 120 IQ points
o Schoenthaler et al. (2000), however, only found these rises for children who were
poorly nourished, rather than those who were already adequately nourished
o Conclusions drawn are that the majority of studies find a positive effect on IQ as a
result of vitamin–mineral supplements, in at least some of the children, on non-
verbal measures of intelligence (e.g. Benton, 1991)
Heritability
• Neisser et al. (1996) suggest that the heritability of IQ is around .75 by late adolescence
o Since we know that it is not genetics that has led to this change in IQ scores due to it
being over such a short time, this suggests that with the environment only accounting
for .25 of the variances in IQ scores, it has changed an implausible amount
o This first raises questions as to the accuracy of our heritability estimates and how we
measure them, and that we are underestimating the impact of the environment on
the variances seen in IQ
Gene x Environment Correlations
• This may instead be evidence of the reciprocal effects between genes and the environment
such that our genetics, in some way, influence our exposure to environmental factors
• Moreover, the multiplier effects may inflate the effects of genes on the environment
o For example, having a higher IQ may lead to them being in an environment that further
increases their IQ, increasing their IQ, increasing the chance of them being in an
environment that increases their IQ, and this carries on…
o Multiplier effects happen at a societal level—external factors may cause a person’s
IQ to rise, improving the environment of others and to their IQ also rising, and so on…
The Nutrition Hypothesis vs The Cognitive Stimulation Hypothesis
• Lynn (1990) initially set up two opposing hypotheses, developed by Neisser (1998) and Flynn
(2003)
• The nutrition hypothesis sees nutrition as part of a nurturing environment, increasing
intelligence, height and lifespan, improved health, and decreased rates of infant disease
• If this were true, intelligence increases would predominantly be seen at the lower end of the
distribution where deprivation is most severe (Flynn, 2003)
3
BSc Psychology Year 1 Applications and Issues in the Study of Intelligence
APPLICATIONS AND ISSUES IN THE
STUDY OF INTELLIGENCE
UNDERSTAND THE ‘FLYNN EFFECT’ AND DESCRIBE POSSIBLE
EXPLANATIONS.
THE FLYNN EFFECT
• The Flynn effect describes the continued year-on-year rise of average IQ test scores in most
industrialised societies throughout the 20th Century
o It is not necessarily that we are seeing an increase in intelligence itself, but that the
increase is in the ability for people to solve abstract problems
• When new IQ tests were established, scores would be compared between the old and new
versions to test the validity of the new test
o Flynn found that participants averaging 100 on a revised (1972) Wechsler Intelligence
Scale for Children, also averaged 108 on the Wechsler Intelligence Scale for Children
(1947/1948)
o Higher scores on the older test demonstrated that they were finding the older test
easier, setting higher standards for average IQ over time
• Between 1952 and 1982 the average IQ score of Dutch men increased by 20 points—
reflecting a 1 SD increase in IQ (Flynn, 1987)
• Flynn (1984) found that white Americans gained 14 IQ points between 1932 and 1978, an
average of .30 IQ points per year
o This average growth per year was then found from 14 countries (Flynn, 1987)
o The highest rises were found in the non-verbal tests (fluid intelligence), with an
average of a 15 IQ point increase per generation
o The lowest rises were in verbal tests (crystallised intelligence), with an average of 9
IQ point increase per generation
EXPLANATIONS FOR THE FLYNN EFFECT
• Flynn argued for environmental explanations of this effect, since the increases are too rapid
to be due to genetic changes
Length of Schooling
• People are now attending school for more years than older generations did (Flynn, 1998;
Neisser, 1998; Williams, 1998)
• Research found that length of schooling was an important predictor of scores on verbal IQ
tests, and more important than age
o Although this trend differs from Flynn’s data in which verbal tests have lower rises in
IQ scores than non-verbal tests
o Therefore, Flynn and Williams argue that this is not a good explanation for the secular
rise in IQ test scores through generations
1
,4PAHPDFF Psychology and the Individual Week 5
BSc Psychology Year 1 Applications and Issues in the Study of Intelligence
Test-Taking Sophistication
• We now promote a culture for taking tests, which may mean that we have more practice with
them and therefore, have become better at taking them
o Our educational system is changing since we are encouraging more abstract thinking
and teaching students how to learn
• Flynn (1998) and Williams (1998) argued that teaching is increasingly being geared to certain
kinds of achievement tests
o For example, ideas about spatial reasoning are new ideas that may not have been
recognised in the early twentieth century
• Therefore, knowledge of intelligence tests by those taking them, as well as parents and
schools, may be leading to the increases
o However, knowledge of IQ tests themselves is unlikely to explain the Flynn effect’s
emphasis on non-verbal rather than verbal aspects of intelligence
o Moreover, increased familiarity with IQ tests does not significantly increase IQ points
(children taking the test twice only gain five or six points; Williams)
Child-Rearing Practices
• Parents today are more interested in their children’s intellectual development, and may
therefore be doing more to develop it (Flynn, 1998; Williams, 1998)
o For example, Sesame Street was created to provide early mental stimulation to raise
children’s awareness and intelligence
Head Start
• The Head Start Programme, which aims to narrow the gap between disadvantaged children
and other children in vocabulary, numeracy, and writing skills
o However, although children attending the programme showed an initial increase of
IQ points, after 2-3 years, these are often lost and the increases don’t remain superior
to disadvantaged children not in the programme (Locurta, 1991; McKey et al., 1985)
• Therefore, early childhood experience and intellectual promotion in early childhood cannot
fully explain the Flynn effect
The Cultural and Technological Age
• The growth of visual media may have made us become more visually aware
o Children spend more time learning through visual media, rather than just learning in
a classroom setting
o Adults have become more used to processing complicated visual information
• This exposure to complex visual media has produced genuine increases in a significant form
of intelligence—visual analysis
• Greenfield (1998) and Schooler (1998) argue that this may explain the growth of fluid
intelligence, such as in the Raven’s Matrices which only rely on visual material
o However, little direct evidence exists for the visual analysis hypothesis
Nutrition and IQ
• Lynn (1990;1998) argues that nutrition and healthcare improvements are some of the main
causal factors of the Flynn effect
o Nutrition is linked to larger brain sizes, and malnutrition to poor brain development
o Moreover, with nutrition having direct impacts on height increases, this may also be
the case for the brain and its functioning (intelligence)
o However, it is hard to test this since studies today usually use WEIRD samples where
children are relatively well-nourished (including where the effect was observed)
2
, 4PAHPDFF Psychology and the Individual Week 5
BSc Psychology Year 1 Applications and Issues in the Study of Intelligence
• Oddy et al. (2004) found that stopping breast feeding early (<6 months) was associated with
reduced verbal intelligence
o Those who were fully breast fed scored 3-6 points higher on a vocabulary test than
those who were never breast fed
o However, Der et al. (2006) found that the mothers of these children scoring higher
were also more intelligent, and when this was controlled for, there was no significant
relationship between breast feeding and the child’s intelligence
• Qian et al. (2005) found that iodine (an important mineral for the main hormone produced by
the thyroid, aiding metabolism and proper growth) was also linked to mental ability
o Children who received iodine supplements in-utero and after birth scored 8.7 IQ
points higher than those who did not
o This rose to 12 IQ points on non-verbal measures (e.g. Raven’s Matrices) and 17.25
IQ points on non-verbal and verbal measures (e.g. Stanford-Binet)
• Benton and Roberts (1988), contrastingly found no difference in verbal intelligence scores
between those given vitamin and mineral supplements and those not
o However, non-verbal intelligence did increase for those who had the supplements
from 111 to 120 IQ points
o Schoenthaler et al. (2000), however, only found these rises for children who were
poorly nourished, rather than those who were already adequately nourished
o Conclusions drawn are that the majority of studies find a positive effect on IQ as a
result of vitamin–mineral supplements, in at least some of the children, on non-
verbal measures of intelligence (e.g. Benton, 1991)
Heritability
• Neisser et al. (1996) suggest that the heritability of IQ is around .75 by late adolescence
o Since we know that it is not genetics that has led to this change in IQ scores due to it
being over such a short time, this suggests that with the environment only accounting
for .25 of the variances in IQ scores, it has changed an implausible amount
o This first raises questions as to the accuracy of our heritability estimates and how we
measure them, and that we are underestimating the impact of the environment on
the variances seen in IQ
Gene x Environment Correlations
• This may instead be evidence of the reciprocal effects between genes and the environment
such that our genetics, in some way, influence our exposure to environmental factors
• Moreover, the multiplier effects may inflate the effects of genes on the environment
o For example, having a higher IQ may lead to them being in an environment that further
increases their IQ, increasing their IQ, increasing the chance of them being in an
environment that increases their IQ, and this carries on…
o Multiplier effects happen at a societal level—external factors may cause a person’s
IQ to rise, improving the environment of others and to their IQ also rising, and so on…
The Nutrition Hypothesis vs The Cognitive Stimulation Hypothesis
• Lynn (1990) initially set up two opposing hypotheses, developed by Neisser (1998) and Flynn
(2003)
• The nutrition hypothesis sees nutrition as part of a nurturing environment, increasing
intelligence, height and lifespan, improved health, and decreased rates of infant disease
• If this were true, intelligence increases would predominantly be seen at the lower end of the
distribution where deprivation is most severe (Flynn, 2003)
3
