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Chapter 7 The Associative Structure of Instrumental Conditioning.

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Presentation on theme: "Chapter 7 The Associative Structure of Instrumental Conditioning."— Presentation transcript:

1 Chapter 7 The Associative Structure of Instrumental Conditioning

2 The way we talk about Pavlovian conditioning is very ‘cognitive’  we say that animals form mental representations of the relationships among stimuli  animal has a representation of the CS that gets associated with some representation of the US  when we present a CS, it calls up a representation of the US  Instrumental/operant conditioning is now viewed in the same way  subjects/animals are information-processors, not only with respect to stimuli (Pavlovian) but also with respect to their own behavior (operant)

3 3 main components in operant learning situation 1.Stimulus – S (or sometimes S d )  the discriminative stimulus sets the occasion for reward by signaling when the response will be followed by the reinforcer 2. Response – R 3. Outcome – O

4 Associations develop among each of these elements: S-R association  the discriminative stimulus can become directly associated with the response S-O association  the discriminative stimulus can become associated with the outcome (basically a Pavlovian association) R-O association  the response becomes associated with the outcome

5 In recent years, this notion that animals develop mental representations of behavior is probably best shown in the work of Rescorla Rescorla and colleagues have done a # of experiments demonstrating that animals develop R-O associations The typical way to demonstrate R-O association is to train rats to make a response for a particular outcome and then devalue that outcome — should lead to a decrease in responding

6 R-O association Colwill & Rescorla (1985) Training DevaluationTest R1R1 O1O1 LPSucrose R2R2 O2O2 CPfood (Same rats get both) O1O1 LiCL O2O2 nothing R 1 and R 2 Everything is counterbalanced, but for the sake of simplicity say LP = sucrose and CP = food and the sucrose is devalued

7 R-O association  animals should have developed 2 different R-O associations  during test, 20 min with both responses available  they could LP or CP but no outcome was given, i.e., essentially an extinction test  if R 1 evokes memory for devalued or aversive outcome, but R 2 does not, then should see a decrease in R 1

8 R-O association Results:

9  when outcome (reinforcer) was devalued by pairings with LiCl, the response that produced the reinforcer declined  the reason is that subjects remembered the reinforcer as being aversive and therefore devalued the response that was associated with that outcome  so, memory for, or representation of, the goal object is crucial for the execution of the response R-O association Results:

10 S-O association Like Pavlovian CSs, S d (discriminative stimuli) also become associated with outcomes Colwill & Rescorla (1988) S d training Response trainingTest S1S1 R1R1 O1O1 N LPSuc S2S2 R2R2 O2O2 L CPfood R3R3 O1O1 R4R4 O2O2 2 new responses All rats get both S1:S1:R 3 vs R 4 S2:S2:

11 This is essentially what happened S-O association if rat has S-O association (i.e., knew which outcome went with which S d ), then when given S 1 on test, should perform the response that was associated with the same outcome i.e., when given S 1 — should perform R 3 S 2 — should perform R 4

12 S-O association Results:

13 S-O association Results:  in the presence of a particular S d, the rats performed the response that was associated with the same outcome, more than the response associated with the different outcome  evidence for S-O association

14 S-R association  somewhat simpler to demonstrate T BPfood  see more BP during the T than in its absence  Rescorla has shown with devaluation experiments that even with complete devaluation, see some responding due to S-R association for ex., devalue food in the presence of the T, rat still barpresses (but won’t eat the food)

15 In addition to the simple associations of 2 elements (i.e., S-R, S-O, R-O), can also have hierarchical associations  the S d becomes an occasion setter that signals when the response will be followed by a reinforcer S RO R nothing  so, the S d signals the relationship between a response and its outcome S [RO] Hierarchical Associations

16  Recall from Pavlovian conditioning that a CS is only powerful when it reliably predicts a US  When the CS provides no reliable information about the occurrence of the US, then conditioning is weak  The same idea has been applied to the learning of a hierarchical association

17 S RO R nothing Hierarchical Associations In this situation, the S is informative about when the R will be followed by the O S RO R O However, in the second situation, the S is provides no information about when the R will be followed by the O

18 Hierarchical Associations Rescorla (1990) used this idea to obtain evidence for a hierarchical association Training Test S1S1 [R 1 O1]O1] S1S1 [R 2 O2]O2] S2S2 [R 1 O2]O2] S2S2 [R 2 O1]O1] But also, R1R1 O1O1 R2R2 O2O2 S 1 : R 1 vs R 2 S 2 : R 1 vs R 2 4 30-s presentations of both discriminative stimuli, with both responses available Which S d is informative about the R-O relation???

19 Results: Hierarchical Associations

20 Theories of Reinforcement 1. Reinforcement as stimulus presentation What identifies a reinforcer? Thorndike  a stimulus that is satisfying  the problem with this definition is that it is circular

21 Theories of Reinforcement Hull’s Drive Reduction Theory  a biological need upsets the body’s homeostasis and induces a drive state  any stimulus that satisfies the biological need, restores homeostasis, and thus reduces the drive state serves as a reinforcer  the problem with this definition is that many reinforcers do not restore/maintain homeostasis  incentive motivation (response elicited by reinforcer), curiosity, praise, criticism

22 Theories of Reinforcement 2. Reinforcement as behavior A. The Premack Principle  rather than talking about reinforcing stimuli, Premack focused on reinforcing responses  so, instead of saying food is a reinforcing stimulus, Premack said eating is a reinforcing response  the only difference between an operant response and a reinforcer is the probability of occurrence  avoided circularity by defining a reinforcer as a more probable behavior than the ‘operant’ behavior  that is, high probability behaviors will reinforce low probability behaviors, but not the reverse

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24 When a rat is water deprived (E1), it drinks more than it runs. Therefore, drinking reinforces running, but running does not reinforce drinking. When a rat is not water deprived (E2), it runs more than it drinks. Then running reinforces drinking, but drinking does not reinforce running

25 Theories of Reinforcement B. Behavioral Regulation Approaches  expanded on Premack Principle  took into account the animal’s repertoire of behavior in a context  this established the “bliss point”, the optimum distribution of responding for the subject  operant contingencies shift the subject away from the bliss point; the subject behaves so as to approach the optimum distribution as closely as possible

26 Time Studying


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