Vroom introduces three variables which he calls Valence, Expectancy and Instrumentality.
Valence is the importance that the individual places upon the expected outcome of a situation.
Expectancy is the belief that output from the individual and the success of the situation are linked, e.g. if I work harder then this will be better.
Instrumentality is the belief that the success of the situation is linked to the expected outcome of the situation, e.g. it’s gone really well, so I’d expect praise
At first glance this theory would seem most applicable to a traditional-attitude work situation where how motivated the employee is depends on whether they want the reward on offer for doing a good job and whether they believe more effort will lead to that reward.
However, it could equally apply to any situation where someone does something because they expect a certain outcome. For example, I recycle paper because I think it’s important to conserve resources and take a stand on environmental issues (valence); I think that the more effort I put into recycling the more paper I will recycle (expectancy); and I think that the more paper I recycle then less resources will be used (instrumentality)
Thus, this theory of motivation is not about self-interest in rewards but about the associations people make towards expected outcomes and the contribution they feel they can make towards those outcomes.
I like it because it allows for non-motivation, or simply for someone to be unmotivated. It questions the assumption that people know or feel that action leads to result. For many people action does not lead to desired result in their lives, so it is critical for any theory to take this into account.
Other theories, in my opinion, do not allow for the same degree of individuality between people. This model takes into account individual perceptions and thus personal histories, allowing a richness of response not obvious in Maslow or McClelland.
Expectancy theory could also be overlaid over another theory (e.g. Maslow). Maslow describes which outcomes people are motivated by and Vroom describes whether they will act based upon their experience and expectations.