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Pleasure and Pain

The idea that organisms are motivated to pursue pleasure and avoid pain was proposed by the Greek philosopher Epicurus, who called it hedonism. The motivational system that regulates pleasure and pain in organisms is called the hedonic control system.

The opponent process theory

When a system must be delicately controlled, this is best accomplished by balancing it between two forces that act in opposite directions. For example, a car needs both an accelerator and a brake.

Pleasure and pain are powerful and opposite motivational forces. In their effect on behavior, they resemble an accelerator and brake.

Richard Solomon of the University of Pennsylvania suggested that each has opponent processes in the hedonic control system (Solomon and Corbit, 1974). The researchers proposed "CNS mechanisms which reduce the intensity of hedonic feelings, both pleasant and aversive."

Hedonic contrast is one of the phen­omena explained with the opponent process theory. This is the tendency of the pleasure/pain control system to rebound in the opposite direction after an intense experience of either pleasure or pain.

For example, when we had young children, we observed that they often cried or got cranky in the afternoon on Christmas Day, a few hours after we opened presents in the morning. They were not unhappy with their presents; they were just on the rebound from an intensely joyful morning.

What are opponent processes in the hedonic system? What is hedonic contrast?

Contrast or rebound effect can occur in either direction. One can feel a burst of relief and pleasure after finishing a difficult task, such as a final exam. One can feel generally healthy and good after recovering from an illness.

Solomon (1980) expanded his opponent process to explain phenomenon of addiction to either positive or negative phenomena. The latter (addiction to negative phenomenon) may sound surprising, but there are many examples of it: people who enjoy thrill rides, horror houses, scary movies, parachute jumping, and more.

Behaviors that are initially terrifying can become very enjoyable. We discuss how Solomon's theory describes addiction in Chapter 14 in the section on addiction.

Pleasure Centers in the Brain

You may recall from Chapter 2 that so-called "pleasure centers in the brain" were discovered accidentally by James Olds. He implanted an electrode in a rat's septum, part of the limbic system.

Olds was preparing to do avoidance conditioning with the rat, but instead he observed the rat lingering in the area of the cage where it received the brain stimulation. Olds realized he had stumbled on an area of the brain that produced pleasure.

How did Olds discover "pleasure centers" in the brain?

Olds set up an apparatus in which the rat could self-administer rewarding stimulation. Each time it hit the bar that stuck out from the side of the chamber, an electrical stimulus would be delivered to the pleasure centers.

Olds and colleagues showed that a rat would press a bar up to 3000 times an hour for rewarding brain stimulation. In another experiment, a rat pressed a bar every two seconds for 20 days, a total of 850,000 self-stimulations.

Dopamine and the Pursuit of Enjoyment

The neurotransmitter dopamine is implicated in reinforcing events at the neural level. It is released in the neural circuits of rats when they look forward to reinforcing brain stimulation (Steinberg et al., 2014).

Dopamine is said to activate a Behavioral Activation/Approach System (BAS) sensitive to stimuli associated with reward. It activates behavior seeking rewards. Projections from dopamine-rich areas in the substantia nigra and the ventral tegmental area (VTA) project into the prefrontal area of the brain.

Panksepp (1998), in the book Affective Neuroscience, made the point that seeking behavior is different from reinforcement. Activation of the dopamine system causes rats to exhibit greater levels of activity such as excited sniffing behavior. Once the rat finds food and consumes it, dopamine and activation levels decrease.

In humans, the analogous behaviors (most affected by dopamine-boosting drugs such as cocaine and ampheta­mines) are behaviors such as gambling or seeking sex. Scientists now accept that dopamine is involved in the lure of addictive drugs.

Virtually every drug, when anticipated by an addict or habitual user, leads to a rise in dopamine levels. Even cannabis, which has a unique drug action unlike stimulants or opiates, gives regular users a burst of dopamine when they anticipate it. So it is not the chemical action of cannabis that boosts dopamine levels: it is the pleasure of seeking a reinforcer.

Many other learned preferences are associated with raised dopamine levels. Virtually every time scientists look for evidence that dopamine levels are raised by anticipation of pleasure, they find it.

Richard Depue, professor of human development and family studies and director of the Laboratory of Neurobiology of Personality and Emotion at Cornell, refers to a personality trait he calls positive emotionality. His studied this trait used ritalin, a drug related to amphetamines and long used for the treatment of ADHD.

People with more sensitivity to ritalin rated higher on Depue's positive emotionality index. "When our dopamine system is activated, we are more positive, excited and eager to go after goals or rewards, such as food, sex, money, education or professional achievements," according to Depue (Lang, 1996)/

Dopamine is associated with anticipation of sex, drugs, drinking, getting money, winning competitions, and religious worship. Religious worship? Yes, Previc (2006) summarizes the relevant research showing "dopaminergic activation as the leading neurochemical feature associated with religious activity." Dopamine is apparently a marker for the purusit of enjoyment of any type.


Lang, S. S. (1996, October 24) Dopamine linked to a personality trait and happiness. Cornell Chronicle. Retrieved from:

Panksepp, J. (1998). Affective Neuroscience: The Foundations of Human and Animal Emotions. New York: Oxford University Press.

Solomon, R. L. & Corbit, J. D. (1974) An opponent-process theory of motivation: I. Temporal dynamics of affect. Psychological Review, 81, 119-145.

Solomon, R. L. (1980) The opponent-process theory of acquired motivation: The costs of pleasure and the benefits of pain. American Psychologist, Vol 35, 691-712.

Steinberg, E. E., Boivin, J. R., Saunders, B. T., Witten, I. B., Deisseroth, K., & Janak, P. H. (2014) Positive reinforcement mediated by midbrain dopamine neurons requires D1 and D2 receptor activation in the nucleus accumbens. PLoS ONE, 9,: e94771. doi:10.1371/journal.pone.0094771

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