Using a feedback loop model, the theory suggests that, in order to achieve a goal, there must be an input function (perception of current state), a comparator (claim differences between current and desired states), an output function (behavior aimed at reducing discrepancy) and an impact on environment. There are two systems: discrepancy-reducing loops, which induces movement towards desired states; discrepancy-enlarging loops, moving away from anti-goals. Cognition involves expectancies and disengagement, while emotions are related to satisfaction of progress toward a goal.
Posited by Michael Scheier and Charles Carver in 1982.