Spencer, Herbert (1820–1903) First a follower of Lamarck and then of Darwin. Spencer applied Darwinian principles to society by saying that society should maintain a laissez-faire policy so that the ablest individuals could prevail. Spencer’s position is called social Darwinism.
Spencer–Bain principle: The observation first made by Bain and later by Spencer that behavior resulting in plea- surable consequences tends to be repeated and behavior resulting in painful consequences tends not to be.
Stern, William (1871–1938) Coined the term mental age and suggested the intelligence quotient as a way of quantifying intelligence.
Struggle for survival The situation that arises when there are more offspring of a species than environmental resources can support.