Can't Separate Nature and Nurture

Who has genetic similarities?

Identical twins, non-identical twins and family members

What does the biological approach argue?

Any similarities in the way that they look or behave must be genetic

How is there a confounding variable?

They're exposed to similar environmental conditions

What does the exposure of similar environmental conditions mean?

Findings could just as easily be interpreted as supporting nurture rather than nature.

What else does this approach have?

Difficulty accounting for the fact that, in research studies, Dz twins often show higher concordance rates than siblings

How is the high concordance rate of D Z twins than siblings likely to be explained by?

The influence of nurture as Dzs and siblings both have about 50% on average genes in common.