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Transcript
Learning Learning “relatively permanent change in an organism’s behavior due to experience” HOWEVER: what most psych texts call “Learning” the rest of us call “motivation” “Learning” = learning what is rewarding and what isn’t. Association We learn by association Our minds naturally connect events that occur in sequence Aristotle 2000 years ago John Locke and David Hume 200 yrs ago Associative Learning learning that two events occur together two stimuli a response and its consequences Association Event 1 Event 2 Learning to associate two events Sea snail associates splash with a tail shock Seal learns to expect a snack for its showy antics Classical or Pavlovian Conditioning Classical Conditioning organism comes to associate two stimuli begins with a reflex (note that humans don’t have many of these) a neutral stimulus is paired (associated) with a stimulus that evokes the reflex neutral stimulus eventually comes to evoke the reflex Classical or Pavlovian Conditioning Ivan Pavlov 1849-1936 Russian physician/ neurophysiologist Nobel Prize in 1904 studied digestive secretions Maybe you’ve heard of “Pavlov’s dogs”… Pavlov’s Classic Experiment Before Conditioning UCS (food in mouth) UCR (salivation) During Conditioning Neutral stimulus (tone) No salivation After Conditioning UCS (food in mouth) Neutral stimulus (tone) UCR (salivation) CS (tone) CR (salivation) Classical or Pavlovian Conditioning Unconditioned Stimulus (UCS) effective stimulus that unconditionallyautomatically and naturally- triggers a response Unconditioned Response (UCR) unlearned, naturally occurring automatic response to the unconditioned stimulus salivation when food is in the mouth Classical or Pavlovian Conditioning Conditioned Stimulus (CS) previously neutral stimulus that, after association with an unconditioned stimulus, comes to trigger a conditioned response Conditioned Response (CR) learned response to a previously neutral conditioned stimulus Dr Fred’s handy guide to classical conditioning 1 – remember that humans salivate to the smell of food just like dogs (reflex!) 2 – freshly baked donuts smell great 3 – so…. Dr Fred’s handy guide to classical conditioning Modern Classical Conditioning Classical or Pavlovian Conditioning Spontaneous Recovery reappearance, after a rest period, of an extinguished CR Generalization tendency for a stimuli similar to CS to evoke similar responses Interstimulus interval Time between the CS and the UCS Optimal usually .5-5 seconds but Garcia effect! Classical or Pavlovian Conditioning Blocking Prior learning hinders later learning e.g., dog learned to salivate to bell, now use a light – ineffective! Latent inhibition early exposure to a neutral stimulus without a UCS slows later learning of a CS-UCS association for that stimulus Prepared learning Some responses easier to learn - evolutionary predisposition to that response Operant Conditioning (aka “Behaviorism”) Operant Conditioning type of learning in which behavior is strengthened if followed by reinforcement or diminished if followed by punishment Law of Effect Thorndike’s principle that behaviors followed by favorable consequences become more likely and behaviors followed by unfavorable consequences become less likely Behaviorism John B. Watson viewed psychology as objective science generally agreed-upon consensus today recommended study of behavior without reference to unobservable mental processes not universally accepted by all schools of thought today Behaviorism B.F. Skinner (1904-1990) elaborated Thorndike’s Law of Effect developed behavioral technology: The “Skinner Box”… Operant Chamber Skinner Box soundproof chamber with a bar or key that an animal presses or pecks to release a food or water reward contains a device to record responses Operant Conditioning = another form of associative learning We learn to associate a behavior and its consequence Hot stove = pain Some terms in both classical and operant conditioning Acquisition the initial stage of learning, during which a response is established and gradually strengthened in classical conditioning, the phase in which a stimulus comes to evoke a conditioned response in operant conditioning, the strengthening of a reinforced response Some terms in both classical and operant conditioning Discrimination in classical conditioning, the ability to distinguish between a CS and other stimuli that do not signal and UCS in operant conditioning, responding differently to stimuli that signal a behavior will be reinforced or will not be reinforced Some terms in both classical and operant conditioning Extinction diminishing of a CR in classical conditioning, when a UCS does not follow a CS in operant conditioning, when a response is no longer reinforced Operant Conditioning Positive reinforcement Negative reinforcement BOTH are rewards Both escape learning and avoidance learning can occur with negative rein. Positive punishment Negative punishment BOTH are punishments Operant Conditioning Shaping conditioning procedure in which reinforcers guide behavior toward closer approximations of a desired goal Successive Approximations reward behaviors that increasingly resemble desired behavior Chaining Stringing together sets of previously shaped behaviors Principles of Reinforcement Primary Reinforcer innately reinforcing stimulus satisfies a biological need Secondary Reinforcer conditioned reinforcer learned through association with primary reinforcer Mechanisms of Reinforcement Drive reduction (homeostasis) Association (secondary reinforcers) Behavioral Approach System (BAS) Distinct neural pathway for reward (left PFC) Dopamine Behavioral Inhibition System (BIS) Distinct neural pathway for anxiety (right PFC) Norepinephrine Fight or Flight system (FFS) – sympathetic NS Schedules of Reinforcement Continuous Reinforcement reinforcing the desired response each time it occurs learning occurs rapidly extinction occurs rapidly Partial Reinforcement reinforcing a response only part of the time results in slower acquisition greater resistance to extinction Schedules of Reinforcement Fixed Ratio (FR) reinforces a response only after a specified number of responses faster you respond the more rewards you get different ratios very high rate of responding like piecework pay Schedules of Reinforcement Variable Ratio (VR) reinforces a response after an unpredictable number of responses very hard to extinguish because of unpredictability And just in case you think this stuff only applies to rats… Skinner boxes for humans Another form of variable ratio reinforcement Schedules of Reinforcement Fixed Interval (FI) reinforces a response only after a specified time has elapsed response occurs more frequently as the anticipated time for reward draws near Schedules of Reinforcement Variable Interval (VI) reinforces a response at unpredictable time intervals produces slow steady responding like pop quiz Schedules of Reinforcement Number of responses 1000 Fixed Ratio Variable Ratio Fixed Interval 750 Rapid responding near time for reinforcement 500 Variable Interval 250 Steady responding 0 10 20 30 40 50 Time (minutes) 60 70 80 Punishment Punishment aversive event that decreases the behavior that it follows powerful controller of unwanted behavior Problems with Punishment Punished behavior is not forgotten, it's suppressed- behavior returns when punishment is no longer imminent Causes increased aggression- shows that aggression is a way to cope with problemsExplains why aggressive delinquents and abusive parents come from abusive homes Regression to the mean - fools the punisher More Problems with Punishment Creates fear that can generalize to desirable behaviors, e.g. fear of school, learned helplessness, depression Does not necessarily guide toward desired behavior- reinforcement tells you what to do-punishment tells you what not to doCombination of punishment and reward can be more effective than punishment alone Using punishment wisely The “hot stove” rule: Punishment should be: Immediate Consistent Impersonal Cognitive Learning (aka Cognitive-social learning) Cognition thinking; information processing input - processing/storage - output Cognition = information processing and storage (memory) includes judgment, motivation, emotions, etc. Cognitive Learning Cognitive Map mental representation of the layout of one’s environment example- after exploring a maze, rats act as if they have learned a cognitive map of it Latent Learning learning that occurs, but is not apparent until there is an incentive to demonstrate it Social Learning Observational Learning learning by observing and imitating others {opportunity to practice!} Modeling process of observing and imitating behavior Vicarious reinforcement (conditioning) observing another’s consequences Tutelage and mentoring Cognitive Learning (aka Cognitive-social learning) More on this in chapter 7…