The economics of behavior ultimately boil down to the efficient use of energy, as energy is obviously required for all behavior. In this sense, one can approach behavior as one does physics, at least in terms of mood and motivation.
Some of the implications are interesting. For example, a principle that applies in microeconomics is also applicable here. It is the requirement that marginal benefit equal marginal cost. To summarize for the present purpose, the energy expended on a given behavior will equal the subjective benefit, as either considered in units of energy or mood, with the latter being the ultimate currency into which all needed resources are converted.
I see mood as simply the sum of all options for net beneft(benefit - cost), discounted for time. So, not only will the energy expended in behaviors associated with each option reflect net motivation, which is obvious, but over a range of behaviors, can also reveal average mood, as previously more precisely defined.. This is when compared to some baseline measurements, which means to compare newer observations to older ones. So, the rate of change of average energy expenditure with respect to average net benefits will correspond to a range of the curve for mood, or a range on the derivative of the mood curve, to be more specific. This gives the average mood level.
The measurement of oxygen consumption, just one among other approaches, can reveal energy consumption. The measurement can be made with a respirometer, for example.
I will post about other approaches to measuring mood a various later times.
Quantitative Psychological Theory and Musings