 Both genetic assimilation and the related Baldwin effect are theories of phenotypic plasticity, where aspects of an organism's physiology and behaviour are affected by the environment.The evolutionary ecologist Erika Crispo states that they differ in that genetic assimilation decreases the level of plasticity (returning to Waddington's original definition of canalization; whereas the Baldwin effect may increase it) but does not change the mean phenotypic value (where the Baldwin effect changes it).Crispo defines genetic assimilation as a kind of genetic accommodation, "evolution in response to both genetically based and environmentally induced novel traits", which in turn is in her view central to the Baldwin effect.