Daniel Pink’s Drive: The Suprising Truth About What Motivates Us (2009) and Two-Factor Theory (aka Herzberg’s Theory) published in 1959, by Herzberg, Mausner and Snyderman.

The Two-Factor theory explains the different factors which motivate and demotivate. Herzberg discovered that the absence of some factors led us to feel demotivated, but their presence alone wasn’t motivating; these he termed ‘hygiene factors’. For example being paid less than your peers is likely to demotivate, but being paid fairly is unlikely to lead to high levels of motivation on its own.