The Brain Reinforces Its
- Repeating a behavior reinforces it.
- Cancelling a behavior makes the desire to do it
Emotional Behavior Is Largely Learned
|Conditioned learning: the learning depends on repeating
conditions in which events are closely associated, in time and
meaning. In Pavlov's original experiments: 1) Dog naturally
likes food, salivates at the thought of eating (no learning
required -- called "unconditioned" stimulus. 2) Sound from
tuning fork is heard by dog, but has no meaning related to food.
3) When sound given immediately before food, when repeated many
times, dog learns to associate the two. 4) Upon hearing
the sound, dog anticipates food, even though none is present.
Both sound and the response are now conditioned.
Another Kind of Conditioning: Operant Conditioning
||Another kind of learning is called "operant
conditioning." This is how animal trainers teach circus animals
and show animals to do tricks. They "shape" a new behavior
for an animal in a series of small steps, giving a reward when the animal
accidentally performs the desired behavior. At each step, the animal
learns an association between the behavior and the reward.
You can perform this experiment on a "cyber
here. In this simulation, the bird occasionally pecks at a spot
on the wall of its cage. If you give him a food pellet each time
he pecks, he will start pecking much more. If you stop rewarding, he
will slow down or stop pecking. See also
Activity #3 for an experiment on conditioning.
When a stimulus activates the "reward system" in the
brain, repeating the stimulus can produce compulsive behavior to seek
that stimulus. This can lead to additions, such as drug addiction,
compulsive gambling, or over-eating. In other words, the brain learns to
The brain's "reward system" is driven partly by the
neurotransmitter, dopamine and norepinephrine. If neurons in the reward
system are getting bathed in these transmitters, you feel good. Note the
structural similarity of these two transmitters.
People with Behavioral Disorders May Have Low
Brain scans, averaged over 5 obese people and 5 people of normal
weight, with the scan tuned to detected receptor molecules for dopamine.
The bright areas are where the dopamine receptors are. The obese people
had fewer dopamine receptors. That is, their reward system was not
getting the normal amount of stimulation. Similar dopamine-receptor
deficiencies have been seen in drug addicts.
Source: National Institute of Drug Abuse.
The obvious interpretation is that obese people don't
get enough "reward" from life, and that they over-eat to compensate.
Another possibility is that their over-eating over-stimulates the
dopamine system and causes the dopamine-receptor system to
"down-regulate." That is, the brain quits making as many receptors
because there is a super-abundance of dopamine. Receptor down-regulation
from over-stimulation has been well documented in numerous other kinds
Can you think how to test that possibility?
|| Craving for any sort of drug
(alcohol, tobacco, cocaine, etc.) seems to involve this same
dopamine reward system found in obesity. Normal rewarding things,
like eating ice cream or a good steak, trigger the release of
dopamine in the reward system. This dopamine is soon destroyed or
taken back up. But taking addictive drugs tend to promote sustained
high levels of dopamine - a chemical "flood."
This creates a problem. The neurons that make dopamine
shut down for a while ("down regulate" as we mentioned above). To get
the same happy, feel-good experience, ordinary rewards, like ice cream
or steak, no longer make us happy. The addict has to take the drug to
experience that same intense feeling of reward. The addict is also
driven by the desire to avoid the suffering experience the he feels
without the drug.
Practical Preventive Measures
- Don't do things that can cause you harm, even if
they "feel good" at the time.
- Don't repeat behaviors that are bad for you.
- Substitute "good" reinforcers for "bad" ones.
Brain Controls Movement