Complex sentence: John William Atkinson, also known as Jack Atkinson, (December 1923-October 27 2003) was an American psychologist who pioneered the scientific study of human motivation, achievement and behavior.
Split into simpler sentences: John William Atkinson, also known as Jack Atkinson, (December 1923-October 27 2003) was an American psychologist. Atkinson pioneered the scientific study of human motivation, achievement and behavior.