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Intelligence. 2.2 Genetics and behaviour Discuss the extent to which genetics influence behaviour. IQ. What is intelligence quotient (IQ)? Should indicate one’s genetically endowed intellectual potential. IQ.

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2.2 Genetics and behaviour

Discuss the extent to which genetics influence behaviour


  • What is intelligence quotient (IQ)?

  • Should indicate one’s genetically endowed intellectual potential


  • The abbreviation "IQ" comes from the German term Intelligenz-Quotient, originally coined by psychologist William Stern.

  • When modern IQ tests are devised, the mean (average) score within an age group is set to 100 and the standard deviation (SD) almost always to 15.

  • Thus, the intention is that approximately 95% of the population scores within two SDs of the mean, i.e. has an IQ between 70 and 130.


Do be a thinker on p 54
Do be a thinker on p. 54 special needs, job performance and

  • Answer questions in groups of 4:

  • Do you think that these tests appropriately evaluate your intelligence?

  • Do you feel that the tests were adequate? Why or why not?

  • How would you change the tests to make them reflect more accurately what you consider to be your “intelligence”?

Intelligent research
Intelligent Research special needs, job performance and

  • Alfred Binet a pioneer in intelligence research, beginning of the 20th century

  • Pr. Richard J. Herrnstein

    & Charles Murray 1994,

    Harvard: The Bell Curve

The bell curve
The Bell Curve special needs, job performance and

  • - The Bell Curve is a best-selling but controversial 1994 book. Its central argument is that intelligence is a better predictor of many personal dynamics, including financial income, job performance, chance of unwanted pregnancy, and involvement in crimethan are an individual's parental socioeconomic status, or education level. The book also argues that those with high intelligence, the "cognitive elite", are becoming separated from those of average and below-average intelligence, and that this is a dangerous social trend.

Intelligence ongoing debate
Intelligence – ongoing debate special needs, job performance and

  • What is it?

  • How can it be measured?

  • Charles Spearman – theorized that there is a general intelligence factor, which he called the “g” factor.

  • Modern intelligence testing attempts to assess this “g”

  • But the question is: where does “g” come from?

  • Is there any difference between men and women?

Research on intelligence family and twin studies
Research on Intelligence special needs, job performance and Family and Twin studies

  • Bouchard and McGue (1981) reviewed 111 studies from around the world of IQ correlations between siblings

    A meta-analysis

    Results: the closer the kinship, the higher the correlation for IQ

    This supports the idea that IQ mostly derives from our genes.

More research
More research special needs, job performance and

  • The Minnesota Twin Study by Bouchard et al 1990

  • Longitudinal study since 1979 & cross-cultural study. Use media to recruit participants.

  • MZA (identical twins raised apart) compared to MZT (identical twins raised together)

  • The mean age was 41 years (start of the study), differ from most other research which is carried out on adolescents

  • Each twin completed 50 hours of testing and interviews

results special needs, job performance and

  • The concordance rates of intelligence can be found in a table on p. 55

  • The study concluded that 70% of intelligence can be attributed to genetic inheritance – leaves 30% to other factors

  • Evaluation?

Critique special needs, job performance and

  • Media coverage to recruit participants (self-selected sample)

  • Ethical concerns – reunited the twins

  • No adequate control to establish the frequency of contacts between the twins prior to the study

  • “equal environment assumption” – are all twins treated the same way (even MZ twins?)

  • No cause and effect

Adoption studies
Adoption studies special needs, job performance and

  • Scarr and Weinberg (1977) and Horn et al (1979) studied parents who raised both adopted and natural children

  • So same environment – any differences should be due to… what?

Results special needs, job performance and

  • Found no significant difference in IQ correlations!

    Very interesting findings

  • Another study by Wahlstein (1997)in France found that transferring children from low socio-economic status family to one where they are high socio-economic status improved childhood IQ scored by 12-16 points (about one SD)

  • Shows that an enriched environment may raise IQ in children.

  • Does this resemble to something else we have studied?

Evaluation of research about iq
Evaluation special needs, job performance and of research about IQ

  • Think critacally – using the following:

  • Method?

  • Ethics?

  • Gender?

  • Culture?

Concluding thoughts on intelligence
Concluding thoughts on intelligence special needs, job performance and

  • Found out (p.56) and answer in writing:

  • What is eugenics?

  • What is the Less effort hypothesis?

  • Does IQ change over time?

  • Which factor is the most important environmental factor in development of IQ?

  • Why has the average mean on IQ tests been going up over the years?

    Finish as homework (including reading the handout “the development of IQ test performance” and summarize the “two sides” with 2-3 arguments on each side – to be handed in