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Chapter 5

Intro to Learning - Chapter 5

7 Pages

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Anneke Olthof

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Learning – Chapter 5  Early investigations of instrumental conditioning o Begin in early work of Thorndike  Original intent to study animal intelligence  Pursued this through empirical research o Puzzle boxes  Placing a hungry animal in puzzle box with food left outside in plain view of animal, goal was to escape the box  Different boxes – different responses o Thorndike’s research significant advance in animal intelligence studies  Did not think they got more intelligent  Interpreted results as reflecting learning of an S-R association o Formulated the Law of Effect  If response in presence of stimulus followed by satisfying event, association is strengthened  If followed by annoying event, S-R association is weakened  Modern approaches to study of instrumental learning o Discrete-trial procedures o Discrete trial procedures – similar to method Thorndike used, animals are removal of animals from apparatus and instrumental response performed only once during trial  Often conducted in some sort of maze o Mazes introduced by W.S Small  Mazes would take advantage of rats’ propensity for small winding passages o Two types of mazes  Straight alley – start box at one side, goal side at other, barrier removed as rat advances, enforcer at the goal  T maze – consists of a start box and alleys arranged in a T shape, with goal box at the end of each, can be used to study more complex questions o Behaviour in maze quantified by how fast animal gets to goal box  Running speed  Increases with exposure / training  Latency  Time it takes to leave start and begin moving o Shorter as training progresses o Free-operant procedures  Free-operant procedures allow animal to repeat instrumental response without constraint over and over again  Skinner box is an example  Skinner  Interested in analyzing form of behaviour representative of all naturally occurring ongoing behaviour  A way of dividing behaviour into meaningful measurable units  Skinner box  Small chamber that contains lever that can be pressed repeatedly o When lever pressed food pellets are given  Operant response – defined in terms of effect that it has on environment  A lever press – can be pressed with right paw, left paw or tail  All functionally equivalent because they have the same effect  Operant outcome is critical measure of success  Operational definition of behavioural success  One does not need to assess whether it has been successful accomplished, environmental outcome keeps the score 1 Learning – Chapter 5 o Magazine training and shaping  Successful training of an operant or instrumental response requires lots of practice and carefully designed training steps  Preliminary steps for establishing lever press  Rat has to learn when food is available in food cup  Involves classical conditioning o Sound of food delivery device repeatedly paired with delivery of food pellet into cup  Food delivery device – food magazine  After enough pairings, sound elicits sign tracking response  Preliminary phase – magazine training  After magazine training, rat is ready to learn required operant response  Shaping – sequence of steps  Rat only gets food when it stands up –anywhere  Rat only gets food when it stands over lever  Only when lever is pressed  Successful shaping of behaviour involves three components  Clearly define final response you wish for subject to perform  Clearly assess starting level of performance  Divide progression from starting point to final target response into appropriate training steps or successive approximations  Execution of training plan involves two complementary tactics  Reinforcement of successive approximatation  Nonreinforcement of earlier response forms  If shaping steps too far apart or spend too much time on one step, progress may be satisfactory o Shaping and new behaviour  Often used to generate new behaviour  Combining familiar responses into new activity  Instrumental conditioning involves construction, or synthesis of a new behavioral unit from pre- existing response components that already occur in subject’s repertoire  Instrumental condition also used to produce responses unlike anything subject ever did  Novel responses created by shaping  Creation of new responses by shaping depends on inherent variability of behaviour  Shaping takes advantage of variability of behaviour and generates responses that are entirely new in trainee’s repertoire o Response rate as a measure of operant behaviour  Free-operant methods permit continuous observation of behaviour over long periods  Provides opportunity to observe changes in likelihood of behaviour over time  Rate of occurrence should be the measure of response probability  Likely responses occur frequently and have high rate  Unlikely responses occur seldomly and have low rate  Instrumental conditioning procedures o Pleasant outcome - appetitive stimulus o Unpleasant outcome – aversive stimulus o Instrumental response may produce or eliminate a stimulus  Depends on the outcome 2 Learning – Chapter 5 Name of procedure Response-Outcome Contigency Result of Procedure Positive reinforcement Positive: response produces appetitive Reinforcement of stimulus response rate Punishment (positive Positive: response produces aversive stimuluPunishment of response punishment) rate Negative reinforcement Negative: response eliminates occurrence of Reinforcement in aversive stimulus response rate Omission training Negative: response eliminates appetitive Punishment in response stimulus rate o Positive reinforcement  Procedure where instrumental response produces appetitive stimulus  If response occurs, appetitive stimulus presented, if response does not occur, appetitive stimulus not presented o Punishment  Instrumental response produces unpleasant stimulus  Effective punishment procedures produce decline in instrumental response o Negative reinforcement  Turns off aversive stimulus  Negative reinforcement increase instrumental response  Response terminates aversive stimulus o Omission training  Withdrawing sources of positive reinforcement  Instrumental response prevents delivery of pleasant stimulus  Also called differential reinforcement of other behaviour (DRO)  Omitting one behaviour causes the reinforcement of another behaviour  Fundamental elements of instrumental conditioning o Essence of instrumental behaviour is that it is controlled by its consequences o Involves 3 elements o Instrumental response  Outcome of procedures depends in part on nature of response being conditioned  Some more easily modified than others  Behavioral variability versus stereotypy  Thorndike – stamping in of an S-R association  Skinner – behaviour being strengthened or reinforced  Both emphasized that reinforcement increases likelihood that instrumental response will be repeated in the future  Encouraged belief that instrumental conditioning produces repetitions of the same response, produces uniformity or stereotypy in behaviour  Criteria for reinforcement is an abstract dimension of behaviour o Behaviour required for reinforcement defined as doing something new, unlike what participants have done before  Response variability basis for instrumental reinforcement  Page and Neuringer 1985 o Pigeons had to peck two response keys 8times to get food  No patterns could be the same for 50 trials  Novel patterns needed to be created to obtain food  Variability in responding increases with reinforcement o Established as an operant 3 Learning – Chapter 5  Absence of explicit reinforcement of variability, responding becomes more stereotyped with continued conditioning  Thorndike and Skinner correct in saying responding becomes more stereotyped with continued instrumental conditioning  Relevance or belongingness in instrumental conditioning  Belongingness – certain responses naturally belong with the reinforcer because of animal’s evolutionary history  Example : Three-spined stickleback o Mating season, males establish territories where they court females but chase away other males o Used male/female as a reinforce  If male, biting of rod increased  If female, effective reinforcement of other responses o Biting does not belong with presentation of female, which would be a sign of aggression  Instinctive drift – extra responses that develop in reinforcement situations which the animals instinctively perform when obtaining the stimulus. o Example :  pigs and food, they would root the food  raccoons and food, would rub it together in a miserly fashion  Behaviour systems and constraints on instrumental conditioning  When animal is food deprived and in situation where food may be encountered, feeding system becomes activated and begins to engage in food-related activities  Instrumental conditioning procedure superimposed on this behaviour system o Effectiveness of procedure in increasing an instrumental response depends on compatibility of that response with pre-existing organization of feeding system  Nature of other responses that emerge during course of training depends on behavioural components of feeding system o The instrumental reinforcer  Quantity and quality of the reinforcer  Quantity and quality of reinforce determines effectiveness of reinforcement o If reinforce small
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