The Development of Measured Intelligence (A2)

The Development of Measured Intelligence

Intelligence is the by product of cognition – especially those aspects concerned with memory, thinking and reasoning.

There are difficulties in defining intelligence precisely.

A popular approach follows Donald Hebb’s (1949) suggestion that:
“Intelligence A” was ones genetic potential for development, given a perfect environment.
“Intelligence B” was the hypothetical stage of development one actually reaches
Vernon (1955) proposed that “Intelligence C” was the little bit of intelligence B that IQ tests measured.

Intelligence tests

In turn of century France, Alfred Binet was asked by the government to design a test which would discriminate between children who had special learning needs and the rest.
It was to be a test of thinking and reasoning for 6-7 year olds. It was not an intelligence test that would claim to test the whole range of intellectual abilities across a wider group. It was a test of mental ability including verbal and non verbal items.
Binet and Simon (1905)

These items were graded by difficulty and many items were graded by age norms i.e. which items could be successfully solved by children at specific ages. It could then be clear that a child of 6.5 years who could not solve the items that a 6 year old could needed remedial schooling.

The idea of Intelligence Quotient

Binets approach was very successful and later the notion of IQ was added by Terman (1916). This was a numerical value that could be used to compare children’s mental abilities
IQ is calculated by finding two factors:
The child’s actual age in years and months (Chronological age – or CA.)
The child’s mental age (MA), as established by the test.

Easiest way for accuracy is to convert both figures into months.

Factors that affect test performance:

Nature the role of genetics
Assessed using research design, kinship studies, adoption studies and gene mapping;

Twin studies:
· Provide an opportunity to conduct a natural experiment where either genetics or environment is constant or varied. Identical twins and non identical twins(Where the person is genetically same or different, are studied either reared together or apart (Environment the same or different.) Identical twins share the same genetic material (MZ. Non identical are similar (DZ.

· Shields (1962) by advertising on TV managed to find 44 sets of twins (MZ) reared apart.
· He found that these individuals had quite similar IQ’s (Correlation of 0.77)
· Also M twins reared together (0.76) This suggested that environment had very little influence on the development of their IQ apparently supporting the fact that genetic factors are greater in importance. DZ twins reared together were significantly lower (0.51)

· Kamin (1977) criticised shields for not noting that in reality the twins actually spent a significant amount of time together and therefore3 were not actually reared apart.
· Swedish Adoption / Twin Study of Aging (SATSA) Pederson et al (1992) followed DZ and MZ twins half of whom were separated before the age of one MZ correlated at 0.80 and DZ at 0.32.

· Scar and Carter-Saltzman (1979) argue that on genetic and behavioural level a surprising number of MZ twins are not actually identical. Psychologists now recognise the extent to which individuals create their own micro-environment (Different friends, teachers and surrounding temperaments from birth.) Different temperaments cause different responses from people in the environment and in return these may have an influence on the development of IQ.

Kinship studies:
· Show that the more closely individuals are related the more similar their IQ, suggesting a genetic component / influence.
· Bouchard and McGue (1981) conducted a meta-analysis of many other studies and calculated for relatives living together a correlation of 0.86 for MZ twins and 0.60 for DZ twins, 0.47 for siblings and 0.38 for parents and offspring.

Adoption studies:
· The Texas Adoption Project – Horn (1983)
o Showed that adopted children’s IQ’s were more closely correlated with their biological rather than adopted mother (0.28 compared with 0.15) though differences were small.
o Years later a study showed the correlation strength had increased and that of the adopted family had decreased. Plomin et al (1988)
· Scarr and McCartney (1983) state that genetics make up preferences biologically and therefore twin and other siblings pick the experiences (Environments) that they prefer. Therefore genetically similar individuals tend towards selected similar environments. (A.k.a. Niche Picking)

Trans-racial adoption studies
· Scar and Weinberg (1976) – American adopted black children in middle class white families were found to have average IQ of 106 at age 7 years. Similar children in low income black families had IQ’s of 97.

Gene Mapping Studies:
· Plomin has claimed to have identified the first gene related to gene intelligence called IGF2R.
· Genes are polygenic – numerous – intelligence is determined by more than one gene. High intelligence will be determined by having a variety of high quality genes. A person with a lot of these plus genes will have a high IQ..IGF was present in 33% super bright’s and only 17% average groups


Nurture: Environmental and Cultural factors
The Rochester Longitudinal Study (Sameroff et al. 1993) is particularly worth mentioning as it found significant correlations between IQ and home factors.



· Hart and Risley (1995) studied the importance of parental involvement in children’s upbringing, the quality of home factors having been identified by Caldwell and Bradley (1978)

Home Observation for Measurement of the Environment (HOME) was developed by Caldwell and Bradley (1978) to establish a checklist of items that can be used when gathering information about the quality of a child’s environment.

Test Factors:
· Rosenthal and Jacobsen’s (1968) “Pygmalion in the classroom” had sixteen elementary school teachers randomly selecting a group of 72 children who were ‘potential bloomers’. When tested later this group gained higher IQ scores than the others. The explanation was that the teachers expected more from these children.

Intelligence and Race
· Environmental argument where limitations may be placed on the potential growth of an individuals IQ via social norms such as Victorian England on “People of colour.”.

· It’s probably impossible to design a IQ test without cultural bias. Williams (1972) developed the “Black Intelligence Test of Cultural Homogeneity” (BITCH) to test Afro-American children. White children did less well on this test.

Conclusion about intelligence.
· We began by noting Donald Hebb’s (1949) suggestion that Intelligence A was ones genetic potential for development given a perfect environment and Intelligence B was the hypothetical stage of development one actually reached.
· He agreed that each person has a genetic potential for achieving a certain level of intellectual capacity (Intelligence A), and that each person reaches a certain level of intellectual functioning (Intelligence B.) He then added the environmental influences were responsible for stretching the rubber band from genetic to actual achievement. Gottesman then argued that society should concentrate on stretching each person’s rubber band to its maximum.
References of note:

Donald Hebb’s (1949) - Intelligence A and B type’s explanation.

Vernon (1955) - Intelligence C type explanation.


Binet and Simon (1905) - In turn of century France, Alfred Binet was
asked by the government to design a test
which would discriminate between children
who had special learning needs and the rest.
It was to be a test of thinking and reasoning
for 6-7 year olds. It was not an intelligence test that would claim to test the whole range of intellectual abilities across a wider group. It was a test of mental ability including verbal and non verbal items.

Terman (1916). - Added to Binets approach and the later
notion of IQ.

Shields (1962) - Twin study. Advertising on TV managed to
find 44 sets of twins (MZ) reared apart. He found that these individuals had quite similar IQ’s (Correlation of 0.77) Also M twins reared together (0.76) This suggested that environment had very little influence on the development of their IQ apparently supporting the fact that genetic factors are greater in importance. DZ twins reared together were significantly lower (0.51)
Kamin (1977) - Twin Study. Criticised shields for not
noting that in reality the twins actually spent
a significant amount of time together and therefore3 were not actually reared apart. Swedish Adoption / Twin Study of Aging (SATSA) Pederson et al (1992) followed DZ and MZ twins half of whom were separated before the age of one MZ correlated at 0.80 and DZ at 0.32.

Scar and Carter-Saltzman (1979) - Argue that on genetic and behavioural level
a surprising number of MZ twins are not
actually identical. Psychologists now
recognise the extent to which individuals
create their own micro-environment
(Different friends, teachers and surrounding
temperaments from birth)
Bouchard and McGue (1981) - Conducted a meta-analysis of many other
studies and calculated for relatives living
together a correlation of 0.86 for MZ twins
and 0.60 for DZ twins, 0.47 for siblings and 0.38 for parents and offspring.

Horn (1983) - The Texas Adoption Project. Showed that
adopted children’s IQ’s were more closely
correlated with their biological rather than
adopted mother (0.28 compared with 0.15)
though differences were small.
Plomin et al (1988) - Years later a study showed the correlation
strength had increased and that of the
adopted family had decreased.
Scarr and McCartney (1983) - State that genetics make up preferences
biologically and therefore twin and other
siblings pick the experiences
(Environments) that they prefer. Therefore
genetically similar individuals tend towards
selected similar environments. (A.k.a. Niche
Picking)

Scar and Weinberg (1976) - Trans-racial adoption studies. American
adopted black children in middle class white
families were found to have average IQ of
106 at age 7 years. Similar children in low
income black families had IQ’s of 97.
Sameroff et al. (1993) - The Rochester Longitudinal Study is
particularly worth mentioning as it found
significant correlations between IQ and
home factors.
Hart and Risley (1995) - Studied the importance of parental
involvement in children’s upbringing.
Caldwell and Bradley (1978) - The quality of home factors in IQ.





Caldwell and Bradley (1978) - Home Observation for Measurement of The
Environment (HOME) was developed to establish a checklist of items that can be used when gathering information about the quality of a child’s environment.
Williams (1972) - It’s probably impossible to design a IQ test
without cultural bias. They developed the
“Black Intelligence Test of Cultural
Homogeneity” (BITCH) to test Afro-
American children. White children did less
well on this test.








Concepts to note:

Intelligence defined.
Intelligence types A, B, and C defined.


CA (Chronological Age)
Cultural Bias
IQ (Intelligence Quota)
MA (Mental Age)
Project Headstart
Rochester Longitudinal Study

The Texas Adoption Project

What do they say or do?
Binnet
Caldwell and Bradley
Hart and Risley
Hebb
Rosenthal and Jacobson
Williams