The answer is Drive Reduction Theory. It is built on the notion that we are determined by basic biological needs like food, water, shelter. Needs motivate our behavior to search for homeostasis (balance) in our physiques. If we miss breakfast, we feel starving. The hunger need energies us to look for food so that we try to get rid of the starvation, as a result bringing us back to a homeostatic condition. These determinations can either be primary or secondary.
