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University of Toronto Scarborough
Rutsuko Ito

Lec04 Instrumental learning vs pavlovian conditioning 1. Share many behavioral features a. Acquisition b. Extinction c. Spontaneous recovery d. Stimulus generalization e. Discrimination f. Contingency g. Laws of association 2. Critical difference a. Instrumental learning independent of pavlovian influences (i.e. CS-US associations) b. GRINDLEY study i. Trained guinea pigs to turn heads left ii. Retrained guinea pigs to turn heads right iii. Suggests that behavior is under control of action-outcome (instrumental) rather than CS-US (pavlovian) conditioning 1. i.e. bidirectional nature of conditioning demonstrates that it is under instrumental control rather than pavlovian control Types of instrumental conditioning 1. Positive reinforcement a. Introducing an appetitive stimulus to reinforce behavior 2. Negative reinforcement a. Removing an aversive stimulus to reinforce behavior 3. Positive punishment a. Introducing an aversive stimulus to decrease behavior 4. Negative punishment a. Removing an appetitive stimulus to decrease behavior 5. Positive contingency a. A response produces the stimulus b. There is a positive contingency when the probability of CS predicting the US is greater than the probability of US being presented alone 6. Negative contingency a. The response terminates a stimulus that was present b. The response prevents a stimulus that would have occurred if there had been no response c. There is a negative contingency when the probability of CS predicting the US is lower than the probability of US being presented alone Methods for measuring instrumental action 1. Two types of methodology in arranging instrumental contingencies a. Discrete trial procedures i. Often associated with mazes in which learning occurs in discrete trials involving animals running down an arm of the maze in order to find reward ii. The subject determines the length of the trial iii. The experimenter determines when the next trial begins iv. Each trial ends with the removal of the subject from the apparatus v. Types of discrete trial procedures 1. Runway / straight alley maze a. Animal placed in the start box b. Barrier is removed c. Animal runs towards goal box where reward is d. Dependent variable  time needed to reach goal box 2. T maze a. Goal box at the end of each arm b. Used to assess spatial working memory i. Subject is required to remember which of the goal boxes it had collected a reward from in the training trial c. Test phase rewards animal for choosing either the arm opposite to the previously rewarded arm (non-matching to place) or choosing the same arm as the training trial (matching to place) i. Rats naturally tend to alternate between choices in order to explore novel spatial locations 1. Non matching to place reward choices are often impaired by hippocampal lesions 2. Matching to place reward choices are often impaired by medial prefrontal cortical lesions 3. Radial maze a. 6-12 arms emanating from a central platform b. Used to assess many types of learning including i. Spatial working memory ii. Reference memory c. Each trial involves the experimenter placing reward at the end of half of the available arms of the radial maze i. Rat placed in the central platform and allowed to freely explore the maze 1. Dependent variable a. Latency to collect all rewards b. The pattern of entries into rewarded and non-rewarded arms i. Entry into a non-rewarded arm is a reference memory error ii. Re-entry into an already visited arm is a working memory error d. Goal of the task is to learn to collect the rewards using the least number of arm entries i. Usually takes 30-40 trials to get good at this b. Free operant procedures i. SKINNER 1. Skinner box a. Rat learns to press a lever for reward in a free environment b. Operant responses can be varied i. Chain pull ii. Pecking iii. Nose poke iv. Lever pressing c. Dependent variables can be i. Rates of responding ii. Number of responses iii. Latency to respond ii. Operant responses are learned through a number of processes 1. Magazine training a. Animal learns that food is available in the pellet receptacle or magazine 2. Shaping a. Experimenter reinforces closer and closer approximations for the desired response b. E.g. lever press i. Reward for 1. Approaching lever 2. Sniffing lever 3. Pressing lever 3. Superstitious behaviors a. Development of random behaviors because of accidental pairings with a reward b. Common in humans as well i. Motions a tennis player goes through before serving Actions and habits 1. Instrumental action defined in terms of action (response) and outcome (reinforcer) a. However, early theorists of instrumental learning believed that instrumental action involves the formation of associations between the stimulus and response THORNDIKE 2. THORNDIKE study a. Puzzle box i. Examine how a cat would learn to escape from the box by operant behaviors to obtain food ii. Could not convince the cat to open the latch by putting paw on it iii. Instead, motivated the cat to open the latch by strengthening the ass
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