Quantitative Psychological Theory and Musings

Sunday, June 14, 2009

What is Mood? A Behavioral Economic Definition

This first post may seem at least a bit technical, despite the simplifications.  I just want to offer some of the more precise foundations of the approach this blog will discuss.  Simpler, more concise posts on mood will follow.  I start with an operationalized definition of mood, which I represent as what we really mean when we talk about higher or lower states of affect.

Mood simply represents the sum of the perceived available, temporally discounted net reinforcing options, or the baseline rate of intake of reinforcement, in the context of a required net inake. For example, at a given level of energy expenditure, there is a required net caloric intake. The net intake of this specific category of reinforcer (energy) is translated into mood, which is the ultimate currency in the brain.

Around 80% of people are risk/loss averse, meaning they value losses more heavily than gains. This is increasingly true as mood decreases, because there is the equivalent of the wealth effect operating on the brain. Hence, as mood decreases, net reinforcement shifts toward more immediate, more "profitable" gains, as resource conservation occurs. This is manifest as greater tendencies toward promiscuous behavior, preference shifts toward higher calorie foods (unless body image supresses it), and drug abuse. Also, because the value of losses loom ever greater than that of gains, negative emotional responses are augmented while positive ones are diminished.

This can be summed up nicely here with a greatly simplified, but relevantly complete mathematical expression of net motivation. U = N [ g / ( h + g ) - L / ( h - L )], where U = net utility or net motivation (subjective net expected gain or loss, or you can call this simply demand), g = objective gain, L = objective loss or response cost, h = baseline rate of intake of reinforcement, or "have" (mood), and N = required rate of reinforcement (Need). Ultimately, this is a model relating the required rates of intake of unconditioned reinforcers to the resources perceived available, with the ultimate goal being to optimize inclusive fitness, or reproductive success.  This is a reinterpretation of the various matching law models.

This would explain why, for example, girls with relatively higher stress levels actually enter puberty earlier than girls with lower stress. The brain makes an economic calculation based on environmental input indicating an environment relatively hostile to reproductive success, and hence a higher quantity reproductive strategy is selected for. Girls who have higher stress and enter puberty earlier have more sexual partners on average and have sex earlier than those with lower stress levels.

This equation models depression as well, and clearly defines the crux of the problem. Those who are depressed, perhaps seemingly paradoxically, value gains more heavily, but net motivation decreases because the value placed on losses increases at a greater rate as mood decreases. This is consistent with research, demonstrating, for example, that participants diagnosed with depression are willing to expend less energy for reinforcement, but consume more than the non-depressed when response costs are reduced.

Increases in net motivation allow for greater behavioral investment in seeking natural reinforcement, which can lead to habits, with proper psycho-education, that can maintain higher mood levels sans medication. This should be the ulitmate goal of any plan to treat non-purely neurological depression.

This model also predicts that anti-depressants will offer little beneft for the dysthymic, as the curve for net subjective value (utility) flattens as mood increases. This prediction is consistent with experiment and other data.  The model also suggests explicit roles for dopamine in mood and motivation, as it represents the subjective magnitude of gains and losses. Hence, the model predicts the inverted U-shaped curve for the effects of stimulants on net motivation, and the effects of stimulants on attention and negative emotional behavior.

This is a self- and externally consistent model of mood, emotions, and motivation. Hopefully, this post can allow one to begin to see where this model comes from. Those wanting more references, or who have any questions about how the dots connect, don't hesitate to ask. This is not extremely complex, but it is a different way of thinking about mood, motivation, thinking, and behavior for many.


  1. Interesting. My math is not so good. Your formula was obtained by statistical analysis of large groups of data, fitting a curve to a data plot, something like that?

    From your reference: Anhedonia, as a failure to experience rewarding stimuli, is a key characteristic of many psychiatric disorders including depression and schizophrenia.

    Does the classification of stimuli into positive and negative depend upon the personality of the subject? If he is generally an optimist or pessimist? Happy or angry?

    bill wald

  2. Bill,

    The formula is actually my interpretation of Herrnstein's matching law, which I link to above. There are decades worth of experiments supporting matching.

    In english, this says that motivation with regard to something pleasurable, once accounting for expected gains and losses, is in proportion to the weighted average of that something(pleasurable activity).

    Or to say, the subjective value of doing something is in proportion to the ojective value of that something, divided by all other options for obtaining pleasure of any kind.

    For example, if you are thirsty for 1 pint of water, then the value to you of say, 6 ounces of wather is higher than it would be if you were less thirsty. There is a relationship between the rate at which you drink water, versus the rate you need to take in water(depending on the circumstances), and the amount of water avaible for you to drink, minus any costs of obtaining it. With respect to any pint of water you can buy, the reward will equal the costs of obtaining it. But, how can this work if obtaining a pint of water costs you a pint of water?

    Well, the costs are mostly not in the form of water. They are in the form of anything else you could do other than drink water. The thirstier you are, the more of other activities you are willing to give up to drink some. So, the benefit you get from obtaining the water will equal the cost of obtaining it, but the costs are with respect to otherwise unrelated beneficial behaviors. So, all of these other behaviors you can engage in, along with drinking the water, make up the behavioral manifestation of mood, with mood actually being the intake of pleasure minus any costs of obtaining it. So, mood is like a monetary currency into which all pleasurable or painful events, expected or realized, are converted.

  3. With regard to anhedonia, the ranges of net pleasurable or displeasurable options changes as mood increases or decreases. A range of pleasurable activities enjoyed when moods are higher, may be enjoyed far less when the subjective costs are higher. Hence, there is less motivation, and of course, less emotion elicited with respect to those activities. the same is true of outcomes in general.

    When it comes to whether positive or negative stimuli catagories depend upon personality, they do in some ways. For example, those with relative dopamine insensitivity can tolerate more stimulation seen a positive than someone with more sensitivity. In the latter case, there is too much of a good thing. Also, for some innate reasons, and reasons of experiences, food preferences can differ, and sometimes substantially. The same is true for sexual attraction.

    Also, there is the matter of innate risk profiles. Risk seeking people may find dangerous activities more pleasurable than the risk neutral or risk averse.

    There are some innate tendencies toward happiness, such as you find in those with Down Syndrome. Lower moods do predispose one to more pessimism, as expected(future)net pleasure is low. I hope this answers your question on this matter.

    For more specifics on my model(this is mathy), the difference in my interpretation is that instead of putting behavior on one side of the equation and reinforcement on the other, I simply have N for "need" as a multiplier, relating the basline rate of intake, with an expected gain or loss relative to baseline intake.

    The orginal matching formulation looks like this:

    B1/(Bo + B1) = R1 (Ro + R1), where B stands for "behavior," and R for "Reinforcement"

    B1 is a particular exhibited behavior, and Bo represents all "profit maximizing" behaviors one can engage in. Similarly, R1 is a particular reinforcer and Ro the sum of all net positive reinforcement available.

    The difference in my interpretation is that instead of putting behavior on one side of the equation and reinforcement on the other, I simply have N for "need" as a multiplier, relating the basline rate of intake, with an expected gain or loss relative to baseline intake.

    Now I take that form, with g(h+g), which is the "gross" subjective gain, with g being the objective expected gain. Then L/(h-L) is offered, to represent subjective costs of obtaining a gain(or expected subjective loss, with L as the objective loss.

    I'll do some posts on these issues soon.

  4. Very interesting but I would like to see more specific examples indicating the scope of this theory ; and especially more specific examples relating to economic behavior .

  5. Can you be more specific about examples relating to economic behavior?

    The net motivation function, as mentioned can be considered as the demand function for an individual, with supply being h. Hence, this is the shape of utility at the biological level, which is the only one that matters.