Why would a shared environment have such little effect on personality development?
◦ A shared environment doesn't mean shared experiences or shared reactions to those experiences; what one sibling perceives as "harsh parenting" could be perceived as "typical" by another.
◦ Genetics generally accounts for about 70 percent to 80 percent of the variance explained in personality characteristics; there simply isn't much variation left to be explained by environment.
◦ The shared environment cannot be quantified or defined adequately; therefore, any influence it may have on personality development is likely to be haphazard at best.
◦ "Shared environment" is not a construct that personality psychologists endorse; rather, it is a concept borrowed from sociology and applied inexpertly to the study of personality.
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