Oct14

Oct 14

Heritability coefficients: statistical estimate of the extent to which variation in a characteristic among a groups of people can be attributed to genetic factors

These values do not appply to individuals but rather to variance in a trait across individuals within a specifici group

The fact that weight has a heritability coefficient of .6 does not mean that 60% of a person's weight is due to genetics, it suggests that within that specific group 60% of the variance in weight can be sttributed to genetic factors.

 Because these values are based on variance with a particular group, new heritability coeffcients need to be calculated for each specific group you're studying

We need to make independant estimates for seperate groups

Modern day humans vs hunter gatherers would have very different estimates related to weight.

Twin/adoption studies Understanding how the degree of genetic overlap amongst individuals varies with relation helps us estimate contributioins from genetic factors

The probability of sharing any one particular genes is 100% for identical twins, 50% for parents and children, 50% for siblings and fraternal twins, and 25% for grandparents and grandchildren.

Twin and adoption studies provide a natural experiment that allows us to estimate the variance associated with both genetic and environmental factors

Concordance rates: refer to the rates of co-occurance of a characteristic among individuals In other words, how closely correlated are measures among a particular group?

Higher concordance rates are usually found among individuals who are more highly related to one another (suggesting genetic contributions)

 Groups of studies: 1, identical twins raise togethter: same genetics 100%, same household. 2, identical groups raised apart: same genetics 100%, different environment 3, fraternal twins raised together: same genetics 50%, same environment 4, fraternal twins raised apart: same genetics 50%, different environment

For groups 1 and 2, genetics are consistant and controlled but the environment is different.

 Can only get correlational data from this, but still quite useful

Collecting large amounts of data on many different groups that represent various permutations of relative difference in genetic

These data are from a meta analyses looking looking at heritability estimates for various personality traits across 52 different studies

On average, identical twins are more similar than fraternal (implicating a role for genetics)

At the same time, a role for the environment is also apparent (twins raised together are more alike that those raised apart)

Meta analysis combines data from multiple different studies.

 Minnesoda twin study was a large scale study that attempted to estimate genetic contributions to dimensions related to personality

Estimates ranged from 39%-58% Highest estimates for attitudes toward preservation of life and equality, athleticism, alcohol abuse

Estimates for contributions related to unique experience ranged from 36%-56%

 Shared environment seemed to predict little to nothing related to personality

Remember the importance of both genes and the environment as well as how they interact

For example, genes calibrating the vestibular system may predict proneness to motion sickness, which may predict whether or not someone like rollercoasters (but does not imply a roller coaster enjoyment gene)

Genetic influences seem to account for 50-70% of variance in IQ scores

This implies 30-50% of variance in IQ is not directly tied to genetics, so what accounts for the rest of the variance?

The concept of reaction range refers to the genetically influenced limits within which environmental factors can be expected to exert their effects on any singular organism