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Study Questions
1. What is an instrumental behavior?
An instrumental behavior is a behavior that can be modified by the outcome it
produces.
2. What are the two categories of instrumental behavior?
Actions and habits. The action system acquires expectancies, whereas the habit
system acquires stimulus–response associations.
3. What is Thorndike's Law of Effect?
Outcomes produced by behavior ultimately adapt the animal to the situation by
strengthening and weakening existing stimulus–response (S–R) connections.
Outcomes that are rewarding strengthen S–R connections, whereas nonrewarding
outcomes weaken connections.
4. Describe Tolman’s cognitive expectancy theory. How is it different from Thorndike’s
theory?
Tolman believed that our brains detect and store information about relationships
among all the events provided by a particular experience. Unlike Thorndike, he
believed that instrumental behaviors are purposeful and organized around goals.
5. Explain the term expectancy.
It is a three-term association (S1–R–S2) that includes a representation of the
stimulus situation (S1) that preceded the response, a representation of the response
(R), and a representation of the outcome (S2) produced by the response.
6. What are the four differences between action and habit?
Purpose; sensitivity to outcome; associative structure; flexibility.
7. What is the premise of the reward devaluation strategy?
The reward devaluation strategy is used to determine if the instrumental behavior is
purposeful and goal directed by changing the value of the reward. If the reward is
devalued (reduced), the subject will continue to respond if the response is a habit,
because only actions are sensitive to the value of the reward.
8. What is the discrimination reversal learning strategy?
It tests the flexibility of the system that supports a particular instrumental behavior,
for example by switching the correct lever to press to obtain a reward to the
previously incorrect lever. The rationale for this strategy is that the action system
would facilitate learning changes in the outcome but the habit system would
interfere because it is slow to change.
9. Explain the conceptual model for actions and habits.
An subject has an initial experience composed of a sequence of an antecedent
stimulus (S), a response (R), and an outcome (O) produced by the response. This
experience is represented in two levels of the brain, I and II. With limited training,
the representations in level II are associated with and can support an action. With
extended training, a habit is formed, that is, connections between the stimulus and
response representations in level I become strong enough to support the generation
of an instrumental behavior, without projections back from level II.
10. What is the experimental evidence that the action and habit systems initially compete
for control of instrumental behaviors when the requirements of a situation are reversed?
Pauli’s group did experiments in which specific brain regions that support either
actions or habits were inactivated after learning to press a lever for a reward. Then
they learned a “lever shifting” task that required them to shift to a new, more lever
to get a reward. If the action system was inactivated, rats learned to shift more
slowly. If the habit system was inactivated, they learned more rapidly.
11. What are the effects of cocaine use and chronic stress on instrumental behavior?
Both can interfere with the action system, and this could result in the habit system
controlling instrumental behaviors.
12. What are the components of the cortico-striatal system?
The prelimbic and infralimbic regions of the prefrontal cortex, sensory cortex, and
motor cortex are the cortical components. The striatal component consists of the
dorsomedial and dorsolateral striatum and the nucleus accumbens.
13. What is the evidence that the dorsomedial striatum (DMS) plays an important role in
goal-directed actions?
Damage to the DMS makes rats insensitive to reward devaluation.
14. What are the roles of the basolateral amygdala, prelimbic cortex, and infralimbic
cortex in instrumental behavior?
The amygdala is important for attaching value (good or bad) to a particular
outcome.
The prelimbic region is necessary early in training to build the action system that
controls a specific behavior.
After extensive training, the infralimbic region suppresses the output of the action
system.
15. What is the evidence that the action and habit systems compete?
Either the region of the brain that supports the action system or the region of the
brain that supports the habit system was inactivated immediately prior to the test
session when the response–reward contingencies reversed. Rats with inactivated
action systems learned more slowly to make this adjustment. Rats with inactivated
habit systems learned faster.
16. What is the evidence that the DMS and DLS actually store memories needed to
support habits and actions?
Injecting the PKM inhibitor ZIP into these regions erased the memories that
encoded habits and actions, respectively.
17. What is the mesolimbic dopamine system? What is dopamine’s role in instrumental
behavior?
Dopamine neurons are located in the ventral tegmental area (VTA), and their fibers
project into the nucleus accumbens, part of the ventral striatum. Dopamine in the
nucleus accumbens is thought to strengthen the connections between the stimulus
and the response or between the response and the outcome.
18. What is the incentive salience hypothesis?
The incentive salience hypothesis assumes that the reward turns on dopamine
neurons in the ventral tegmental area. In the normal sequence of events that
establish instrumental behavior, the stimulus not only can associate with the
response, it also can get associated with the incentive properties of the outcome.
Subsequently, the stimulus complex itself can elicit strong urges or wants that lead
the individual to seek out the reward.