Are these the most important discoveries in the history of psychology?

From The Blank Slate by Steven Pinker:

“The three laws of behavioural genetics may be the most important discoveries in the history of psychology. Yet most psychologists have not come to grips with them… It is not because the laws are abstruse: each can be stated in a sentence, without mathematical paraphernalia. Rather, it is because the laws run roughshod over the Blank Slate [the idea that everything is learned, nothing innate], and the Blank Slate is so entrenched that many intellectuals cannot comprehend an alternative to it, let alone argue about whether it is right or wrong.

Here are the three laws:

  • All human behavioural traits are heritable.
  • The effect of being raised in the same family is smaller than the effect of the genes.
  • A substantial proportion of the variation in complex human behavioural traits is not accounted for by the effects of genes or families.”

Later Pinker explains the implications the laws have for psychological research. For example:

“The First Law implies that any study that measures something in parents and something in their biological children and then draws conclusions about the effects of parenting is worthless, because the correlations may simply reflect their shared genes (aggressive parents may breed aggressive children, talkative parents talkative children).”

Previously on the Digest: Switching the parents around.

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.