Behavioural genetics• Humans share 93% of genes with rhesus macaque monkeys• Our genes (which are inherited) give rise to development of specific physiological processes that contribute to specific characteristics and behaviour• People may have a genetic predisposition towards a certain behaviour, however without appropiate environmental stimuli, this behaviour will not be manifested.
• Humans have 23 pairs of chromosomes, with approximately 25,000 genes which were passed on from each parent• Genes, the basic unit of heredity, are located on chromosomes• Each gene (or segment of DNA) contains four basic chemicals – identified by the letters A,T,C and G• The particular order of these letters makes up a code for protein synthesis. There are thousands of code (or letter) sequences
Human Genome Project • In 2003 researchers were able to identify the sequence of almost all 3 billion units of DNA (A,T,C,G) and to determine the boundaries between genes and how they are arranged on the chromosome – this is known as the Human Genome Project. • NevertheIess despite this remarkable achievement we still are not able to identify the role of specific genes in specific behaviours.
Genetic research• Are in large extent based on correlational studies – twin studies, family studies and adoption studies.
Intelligence • Beginning of 20th century – a great interest in the role of genetics and behaviour • Alfred Binnet – developed first intelligence test in order to improve the French education system • Is intelligence inherited or is it the result of environmental stimuli?
• Controversial research – 1994 prof. Richard Herrnstein published The Bell Curve – he claimed that the debate about whether and how much genes and the environment have to do with ethnic differences remains unresolved.
• Give me a dozen healthy infants, and my own specified world to bring them up in and Ill guarantee to take any one at random and train him to become any type of specialist I might select – doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors. John B. Watson
• Charles Spearman found that student performance across different subject was positively correlated.• He argued that there is a general inteligence factor that is basis for all inteligence testing attempts – g factor• Now IQ tests are focused on spatial ability, reasoning, divergent thinking and verbal fluency.• Where does this g factor come from?
META-ANALYSIS• Bouchard and McGue (1981) reviewd 111 studies of IQ correlations between siblings from research studies on inteligence from around the world.• It was META-ANALYSIS – statistical synthesis of the data from a set of comparable studies• They found that the closer relationship - the higher the correlation for IQ
Minnesota Twin Study Bouchard et al. 1990• Aim of the study: researchers seek to identify the genetic and environmental influences on the development of psychological traits.• Longitudinal study of 11-17 year-old twins, started in 1979. Involved a week-long of medical and psychological assessment of identical and fraternal twins separated in early life.• This is the most cross-cultural stydywith participants from all over the world.
METHOD & COLLECTING DATA• Medical Assessment: - Psychiatric interview - Medical life history - Standard blood test - Detailed dental & periodontal exams• Psychological Assessment: -Academic ability -Personality & Interests -Family & Social relationships -Mental & Physical health -Psychological Measurements
Concordance rates of inteligence Same person tested twice 87% Identical tins reared together 86% Identical twins reared apart 76% Fraternal twins reared together 55% Biological siblings reared together 47%Researchers determined a heritability estimate of 70% -that is 70% intelligence can be attributed to geneticinheritance
FINDINGS (examples)Separated as infants, twins Gerald (Jerry Levey) and Mark Newman grew up to sharecharacteristics ranging from their firefighting avocation to taste in beer.• Neither of them knew of the others existence• When they first met, they saw their reflection in the other person.• Grew same mustache, wore the same glasses.• Both worked in supermarkets for a while.• Both volunteer fire fighters.• Both men are bachelors and are attracted to the same kind of women.• Both brought up in the Jewish faith but neither is particularly religious.• Both men drink only Budweiser Beer. ( They even hold the can in the same way• Quote - “we kept making the same remarks at the same time and using the same gestures. It was spooky...He is he and I am I, and we are one.”
CRITICISM OF THE STUDY• Bouchard relied on media coverage to recruit participants.• There are some ethical concerns about the way he reunited the twins.• There was no adequate control to establish the frequency of contact between the twins prior to the study.• We cannot assume that twins who are raised together experience the same environment .
ADOPTION STUDY• The inteligence of adopted child is correlated with the intelligence of the adoptive parent – there is no biological link – environmental influence should be evident.• Scarr and Weinberg (1977) and Horn et al (1979)• Focused on parents who raised both adopted and natural children• All children have the same upbringing in the same enviroment, with the same parents
ADOPTION STUDY• Researchers found no significant IQ correlations• In almost all the families in this study the adoptive parent were wealthy, white and middle class, with high IQs, and the adoptive children were from poor, lower-class backgrounds, with lower IQ parents
ADOPTION STUDY• Wahlstein (1997) – well- controlled adoption studies in France• He found that transfering an infant from a family with low socio – economic status to a home where parents have a high socio – economic status improved childhood IQ scores by 12- 16 points
• INTELLIGENCE HAS A LOT TO DO WITH THE ENVIRONMENT AS WELL AS GENETICS• ENRICHED ENVIRONMENT MAY RAISE IQ IN CHILDREN• IT IS LIKELY THAT THERE IS STRONG INTERACTION BETWEEN GENES AND THE ENVIRONMENT TO PRODUCE INTELIGENCE LEVEL
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