4 Instrumental Learning The Basics .pdf

PSY2304Biological Basis of BehaviourInstrumental LearningIan McLarenTo h e a r t h e p r e s e n t a t i o n a s y o u g o t h r o u g h t h e s l i d e s , p l e a s e g o t o t h e S l i d e S h o w m e n u a n d c l i c k on “play from start”. You can also sta...

PSY2304Biological Basis of BehaviourInstrumental LearningIan McLarenTo h e a r t h e p r e s e n t a t i o n a s y o u g o t h r o u g h t h e s l i d e s , p l e a s e g o t o t h e S l i d e S h o w m e n u a n d c l i c k on “play from start”. You can also start from the slide you are on using “play from current slide”. If you want subtitles, then click “always use subtitles”. Finally, you can just look at the slides without hearing me by using the up and down arrows after you open it.What I say in this presentation is either on the slides or in the notes that accompany them (see the notes page in PowerPoint on the View menu). Please click on the slide to advance after I’ve finished speaking or use the forward (and back) arrows to navigate. Contents•History –brief recap.•What is instrumental/operant conditioning? A closer look.•Schedules of reinforcement. Early work•Animal psychologists were studying instrumental learning before Pavlov’s work became known:–Small (rats in scaled-down Hampton Court maze), –Thorndike (puzzle boxes) sStimulus Response ReinforcerInstrumental ConditioningThe concept that followed naturally from Thorndike’s analysis was that of an S->R reflex. When the animal encountered a certain discriminative stimulus S then it emitted the response R. Reinforcement established the link between S and R. Instrumental conditioning procedures•Positive reinforcement = Rèappetitive (more R)•Punishment=Rèaversive (less R)•Negative reinforcement =Rèno aversive (more R)•Omission Training=Rèno appetitive (less R) Reward and reinforcement•Thorndike’s Law of Effect: animals repeat actions that lead to a satisfying state of affairs, and this is called reinforcementbit vague, refined by…•Hull: reinforcement is due to drive reduction, hence the animal will work for food if it is hungry, or for water if it is thirsty etc. Schedules of reinforcement•Extinctionapplies to instrumental conditioning, too –stop giving reinforcers and the response ceases•But we can get away with only reinforcing someof the responses the subject emits, and still get stable conditioned responding•A schedule of reinforcement is a rulefor deciding which responses we reinforce•Different schedules lead to different, highly predictable, patterns of response, instantly recognisable on a cumulative record Simple schedules and their effects•Continuous reinforcement, CRF –reinforce every response•Fixed ratio, FR –reinforce every nth response. Pause after each reinforcement followed by fast responding•Variable ratio, VR –reinforce every nth response on average. Continuous fast responding•Fixed interval, FI –reinforce the first response after time t has elapsed since the last reinforcer. Pause after each reinforcement followed by gradually increasing response rate•Variable interval, VI –same as FI but with a variable time period. Continuous moderate response rate Ratio schedules•reinforcement depends on number of responses–if 1 = continuous reinforcement–if not 1 = partial or intermittent reinforcement–fixed ratio schedule, e.g. FR10–variable ratio schedule, VR10 (the average of responses required equals 10) Interval schedules–reinforcement depends on time interval–Fixed interval, e.g. FI4–variable interval, e.g. VI2 (again the average…) ReadingRequired reading: Pearce, chapter 4

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