David McClelland developed the theory that humans were motivated by three major needs (later expanded to four). These are:

• Need for Achievement: Desire to accomplish something worthwhile, need to set and achieve difficult but realistic goals
• Need for Power (Authority)
• Need for Affiliation: Feeling part of a group, being accepted by others.
• He later developed the notion that the Need to Avoid Failure also plays a major motivation role for some people.