Lyman W Porter and Edward Lawler III derived a substantially more complete model of motivation.
The strength of motivation and energy exected = value of reward + amount of energy required + probability of receiving reward.
Motivation is an extremely significant subject for managers get work done through others. Important characteristics of motivation are individual differ in their motivation, individuals are unaware of motivation sometimes, motivation may change and vary, motivation is a complex one. Maslow, Herzberg, Mc Gregore, V Room and Porter and Lawler are some the important writers on motivation.