Lawrence Wright, Twins: and What They Tell Us About Who We Are, John Wiley & Sons, 1997.
These notes summarize the main findings of twinning studies during the past century which lead to some startling conclusions.
-behaviorism (BFSkinner) argued all behavior genetically based (we are the product of natural selection) but can be programmed in the individual. he denied special genes for altruism/ criminality/ other character trait -what our genes give us is the capacity to adapt to our environment. we are not innately good/ bad, rather determined by our environment. there is no individual responsibility. to change behavior we must design a different environment.
-but twin studies suggests genetic basis to behavior (approximately 50%, ie, 1/2 determined, 1/2 'free will' which we develop by creating our own environment as we mature and become more self-aware)