Multivariate and longitudinal Flashcards
what is multivariate? how does it work?
Multivariate twin analysis focuses on the covariance or correlation between two or more traits, rather than focusing on one at a time. Many aspects of behavior and development are known to be phenotypically correlated; however, such correlations might be the result of shared genetic influence or environmental influences on both. Distinguishing those influences provides valuable insight into the mechanisms underlying each and allows an estimation of how much of the A, C and E is common between traits.
Like univariate analyses, multivariate analyses contrast correlations for MZ and DZ twins where the magnitude of the discrepancy between them indexes a genetic effect, and the magnitude of the correlations regardless of zygosity indexes a shared environmental effect. But in multivariate analyses, the relevant correlation is the cross-trait twin correlation, that is, correlating measure A for twin 1 with measure B for twin 2.
behavioural genetics allow us to go beyond rudimentary nature–nurture questions, to address the..
relationship between and within traits using multivariate analyses of covariance, and longitudinal analyses to explore stability and change.
With multivariate models we can investigate ..
the genetic overlap between different disorders, the continuity of genetic factors at different stages of the illness, and the relation between genetic factors and mediating or environmental variables (eg personality, stressful life events) in the development of illness.
bivariate heritability verse univariate heritability and how to calcualte bivariate heritability?
bivariate heritability indexes the extent to which the phenotypic correlation between X and Y is mediated genetically. (univariate heritability is the extent to which the variance of a trait can be explained by genetic variance; bivariate heritability is the extent to which the covariance between two traits (or the same trait at two ages) can be explained by genetic covariance.
Bivariate heritability is the genetic correlation weighted by the product of the square roots of the heritabilities of X and Y and divided by the phenotypic correlation between the two traits)
