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Learning Ψ 100/101 Nov 20 ‘09 True or False? 1. Lowly animals, like sea snails, behave by instinct and are incapable of learning. 2. Humans are the only animals that can learn behaviors merely by observing others perform them. 3. The study of inner thoughts, feelings, and motives has always occupied a central place in psychology. 4. A person can be more readily conditioned to fear snakes and spiders than to fear flowers 5. With training, pigeons can be taught to discriminate a Bach composition from a Stravinsky composition 6. Negative reinforcement is another term for punishment. 7. Psychologists agree that punishment, regardless of its form, has little effect on Behaviour. 8. Animals learn only when rewards are given. 9. Animals can learn to make virtually any response if consistently rewarded for it. 10. Research indicates that televised violence leads to aggressive Behaviour by children and teenagers who watch the programs Overview What is Learning? Classical Conditioning Pavlov’s Experiments Extending Pavlov’s Understanding Pavlov’s Legacy Operant Conditioning Skinner’s Experiments Extending Skinner’s Understanding Skinner’s Legacy Contrasting Classical & Operant Conditioning Learning By Observation/Other Types of Learning What is Learning? Learning is a relatively permanent change in an organism’s behavior, knowledge, capability, or attitude that is acquired through experience and cannot be attributed to illness, injury, maturation, etc. A change in neural function as a consequence of experience Learning is the process of acquiring knowledge or skill through study, experience or teaching; it is a process that depends on experience and leads to long-term changes in behavior potential Types of Learning Types of Learning Non-associative learning: Learning in which there is no connected stimulus Habituation: The decline in the tendency to respond to nonchanging inconsequential stimuli Sensitization: An increase in the tendency to respond to an event that has been repeated Habituation is affected by stress and gender Stress reduces habituation (as does caffeine) (Beck et al. ’02) Male rats were more affected by stress than female rats Associative Learning = Learning that requires making new associations/connections Learning connected two stimuli to each other Learning to connect a response to its consequences Learning new skills, facts, maps, etc Psychomotor, cognitive, affective, etc. Ivan Pavlov A Unified Theory of Learning Occam’s Razor / Principle of Parsimony / KISS Philosophical foundation -- Associationism (Lock, Hume, etc) At birth, the human mind is a tabula rasa All writing on the tabula is done by experience 1849-1336 Russian physician / neurophysiologist Laws of Learning Nobel Prize in 1904 Contiguity: events/ideas/sensations that occur together are joined together Research on digestive secretions Frequency: the more often events/ideas/sensations occur together, the stronger the link/association between them Intensity: the stronger the intensity of feelings/effects produced by events, the stronger the association between the events Pavlov’s Discovery Pavlov’s Discovery Before conditioning, food (Unconditioned Stimulus, US) produces salivation (Unconditioned Response, UR) During conditioning, the neutral stimulus (tone) and the US (food) are paired, resulting in salivation (UR) After conditioning, the neutral stimulus (now Conditioned Stimulus, CS) elicits salivation (now Conditioned Response, CR) Components of Classical Conditioning: Acquisition Conditioning Application The initial stage of learning when a response is established and gradually strengthened (the phase in which a UCS comes to evoke a CR) 100 % CRs 80 60 40 20 0 1 2 3 4 5 6 Blocks of 10 Trials 7 8 9 Components of Classical Conditioning: Extinction After a rest period, an extinguished CR (salivation) spontaneously recovers, but if the CS (tone) persists alone, the CR becomes extinct again Spontaneous Recovery: Refers to the reappearance, after a rest period, of the extinguished CR Components of Classical Conditioning: Spontaneous Recovery Complete extinction of a response may be difficult to achieve and may require many extinction trials 100 When the US (food) does not follow the CS (tone), CR (salivation) begins to decrease and eventually to become extinguished Components of Classical Conditioning: Generalization Tendency to respond to stimuli similar to the CS is called generalization Conditioned responses occur to stimuli other than the CS used for training 80 % CRs Components of Classical Conditioning: Spontaneous Recovery 60 The more similar the second stimulus is to the initial CS, the more generalization will occur 40 20 0 1 3 5 7 9 11 13 15 17 19 21 23 Blocks of 10 Trials Generalization is a critical feature of learning because we rarely encounter the exact same stimulus twice Components of Classical Conditioning: Discrimination Individual Differences: Generalization Discrimination is the learned ability to distinguish between a conditioned stimulus and other stimuli that do not signal an unconditioned stimulus Discrimination is the ability to distinguish between a CS and other stimuli that do not signal a UCS Implications of Classical Conditioning Little Albert – Fear Conditioning Watson & Rayner (1920) found a very loud noise made by striking a steel bar with a hammer frightened little Albert, an 11-month old infant Albert was induced to play with a docile white lab rat. While so engage, Watson struck the steel bar with the hammer immediately behind the infant’s head. The authors report: “The infant jumped violently, and fell forward, burying his head in the mattress … just as his right hand touched the rat, the bar was struck again. Again the infant jumped violently, fell forward and began to whimper.” 5 weeks later, when the rat was show to the infant, he immediately began to cry … and to crawl away When presented with a white rabbit, Albert feared it nearly as much as the rat Albert was less afraid of a dog or a fur coat Abbert still feared these objects even after 2 months Exogenous Factors that Impact Classical Conditioning Frequency of the CS – US pairing The strength of the CR increases most in the early part of the experiment Consistency Learning is weaker when conditioning and extinction trials are mixed than when the CS and US are paired consistently Consistent pairing makes the CS a better predictor of the US Kamin (1969) conditioned a CS1 – US pair. Then he presented the CS1 together with an additional CS2, and showed that even after many pairings, subjects showed no CR to CS2 Blocking effect: Conditioning does not occur to a CS that has no additional predictive value (Kamin 1969) Exogenous Factors that Impact Classical Conditioning Timing Forward conditioning, with a short interval between the offset of the CS and the onset of the US, produces strong conditioning (but see later) (but see taste aversion) Belongingness (eg, taste belongs with food) Conditioning is easier for CSs that seem to belong to the US Strength of the US Annau & Kamin (1961) varied the intensity of an electric shock (US) paired with a tone (CS), and found that the magnitude of the conditioned fear response dependent on the intensity of the shock Evolutionary Factors that Impact Classical Conditioning Endogenous Factors that Impact Classical Conditioning Autonomic Arousability Some individuals are more reactive than others: Highly arousable individuals will experience any particular US as more intense than less arousable individuals Classical Conditionability CC refers to the ease with which an individual reaches a specified criterion for learning. A twin study (Merrill et al. 1999) showed conditionability of identical twins was more highly correlated than the conditionability of fraternal twins Applications of Classical Conditioning Learning by Observation Prepared Classical Conditioning Children who witness their parent’s fear of a prepared stimulus such as a snake or spider often develop the same fear (Mineka & Cook ’93) Finding suggests that mental representations can function as unconditioned stimuli (scary stories can produce autonomic responses) Evolution prepared us to be afraid of whatever threatened our forebears (snakes, spiders, blood, fire), and as a consequence, we condition differently to these kinds of stimuli Ohman et al (1976) used pictures of snakes, spiders, houses and flowers as CSs and an electric shock as the US. Conditioning was more rapid (and more resistant to extinction) to snakes and spiders than houses and flowers Garcia did research on taste aversion & showed that the duration between the CS and the US may be long (hours), and conditioning may occur in a single trial John Garcia Applications of Classical Conditioning Drug Overdose Death Conditioning can result in bodily reactions occurring in anticipation of the consumption of particular substances Drug Onset Cues … function as CSs, and they elicit compensatory reactions (called drug tolerance) that diminish the effects of taking a drug like morphine (this is why bigger and bigger doses are required to bring about the same effect with extended use of a drug) What happens when DOCs are present but the drug/morphine is not provided? The person becomes hypersensitive to pain Operant/Instrumental Conditioning A form of associative learning in which voluntary responses come to be controlled by their consequences Skinner used the terms operant or instrumental to describe behavior that is strengthened by reinforcement Both reflect the control that behavior has on getting reinforcers from the environment Operant: B/c behavior operates on the environment Instrumental: B/c behavior is instrumental in producing consequences What happens when the drug/morphine is administered to an addict but in the absence of DOCs? There is no conditioned compensatory reaction, and the effect of the drug might be fatal John B Watson: Founder of Operant Conditioning Burrhus F Skinner: Founder of Operant Conditioning 1878 - 1958 1904 – 1990 Psychology as a Behaviorist Views It" (1913), he asserted that psychology should restrict itself to the objective, experimental study of the relations between environmental events and human behavior Behaviorism is the view that psychology should be an objective science that studies behaviour without making reference to mental processes Famous for Little Albert Watson used classical conditioning procedures to develop advertising campaigns for a number of organizations, including Maxwell House, making the “coffee break” a North American custom Operant conditioning is the form of learning in which rats and pigeons were trained to press a lever (or peck a key) in order to obtain a food reward using the Skinner-Box Edward L Thorndike: Founder of Operant Conditioning 1874 – 1949 Law of effect: A given stimulus will elicit a particular response if the response has been regularly followed by satisfaction or pleasure The Stop-Action principle: The particular form of a behavior that first led to success is likely to persist 30 The Skinner Box Operant Conditioning Phenomena Learning Occurs when a response is followed by consequences Extinction Occurs when we no longer follow the operant response with a reinforcer/ment Extinction does not involve punishment Spontaneous Recovery Generalization Schedules of Reinforcement Continuous Reinforcement: Reinforces the desired response each time it occurs Partial Reinforcement: Reinforces a response only part of the time. Though this results in slower acquisition in the beginning, it shows greater resistance to extinction later Schedules of Reinforcement Fixed-ratio schedule: Reinforces a response only after a specified number of responses (e.g., piecework pay) Variable-ratio schedule: Reinforces a response after an unpredictable number of responses. This is hard to extinguish because of the unpredictability (e.g., behaviors like gambling, fishing) Fixed-interval schedule: Reinforces a response only after a specified time has elapsed (e.g., preparing for an exam only when the exam draws close) Variable-interval schedule: Reinforces a response at unpredictable time intervals, which produces slow, steady responses (e.g., pop quiz Schedules of Reinforcement Reinforcement & Punishment Reinforcement: Any consequence that increases the likelihood that the behavior will occur again Punishment: Any consequence that decreases the likelihood that the behavior will occur again Reinforcement & Human Behavior The percentage of times that a severely disturbed child said “Please” when he wanted an object was increased dramatically by reinforcing him for making a polite request. Reinforcement produced similar improvements in saying “Thank you” and “You’re welcome,” and the boy applied these terms in new situations as well (Adapted from Matson et al., 1990). Types of Reinforcement Reinforcement & Human Behavior The effect of delay of reinforcement. The learning score drops rapidly when reward is delayed. Animals learning to press a bar in a Skinner box showed no signs of learning if food reward followed a bar press by 38 more than 100 seconds (Perin, 1943). Types of Reinforcement A reinforcer/ment is any event that strengthens the behavior it follows Primary reinforcer/ment: An innately reinforcing stimulus like food or drink Positive (plus) reinforcement strengthens a response by presenting a typically pleasurable stimulus after a response (eg, getting candy, money, a hug) Conditioned reinforcer/ment: A learned reinforcer/ment that gets its reinforcing power through association with the primary reinforcer Negative (minus) reinforcement strengthens a response by removing an aversive stimulus after a response (eg, turn off seatbelt noise, stop nagging) Intrinsic reinforcement: Reinforcement that derives from the activity itself, rather than from any consequences that might follow Extrinsic reinforcement: Reinforcement that derives from the external consequences of performing the behavior Types of Punishment A punisher/ment is any event that weakens the behavior it follows Positive (plus) punishment weakens a response by presenting an unpleasant/aversive stimulus after a response (eg, getting scolded, shocked, fined) Negative (minus) punishment weakens a response by removing a desired stimulus after a response (eg, withhold TV privileges) Shaping Diction A child who is learning to talk points to her favorite doll and says either “doll,” “duh,” or “dat” when she wants it. Day 1 shows the number of times the child uses each word to ask for the doll. At first, she uses all three words interchangeably. To hasten learning, her parents decide to give her the doll only when she names it correctly. The child’s behavior shifts as operant reinforcement is applied. By Day 20, saying “doll” has become the most probable response. Shaping/Learning to Pay Attention Shaping is the operant conditioning procedure in which reinforcers guide behavior towards the desired target behavior through successive approximations Shaping involves breaking down a complex behavior into a set of steps that can be reinforced in sequence Shaping can be used to establish complex behaviors (eg, to teach a rat to pirouette) Shaping has been used to teach social skills to autistic children (Pollard 1992; Ingersoll & Carter, 2003) Other Applications Behavior modification is a method that uses reinforcement, punishment and extinction as a means of eliminating undesirable behaviors and/or establishing desirable behaviors Other Applications Learned helplessness: When faced with a situation in which no type of behavior produces desirable consequences, we become helpless, and likely depressed A rat raised in a cage where one side of the floor is periodically electrified will quickly learn to escape to the other side By contrast, a rat living in a cage where both side have been electrified for a period of time will not try to escape later on when only one side is electrified … the rat has learned to be helpless Do people learn helplessness? Lack of control and depression are frequently reported by victims of persistent sexual abuse (Strube ’88) What stimuli are effective as CSs? Kamin (’69) and Rescorla & Wagner (‘72) asserted that conditioning happens only when a subject’s ability to predict the US is imperfect The strength of conditioning depends on how much improvement in prediction remains Thus, without knowing a subject’s conditioning history, it is impossible to know whether the pairing of a CS and US will result in learning Assumptions about Learning Associationist principles are sufficient to account for all learning All stimuli are created equal In CC, an organism can be taught a connection between any CS and any US In OC, an organism can be taught a connection between any response and any reinforcer All species learn the same way (the nature of the organism does not matter) Skinner: “Pigeon, rat, monkey, which is which? It doesn’t matter … once you have allowed for differences in which they make contact with the environment … what remains is astonishingly similar” Learning Changes more than Behavior Evidence of cognitive processes during operant learning comes from rats during a maze exploration in which they navigate the maze without an obvious reward. Rats seem to develop cognitive maps, or mental representations, of the layout of the maze (environment). Do we need an O between S + R? Razran (’69) experiment with words as CS and tiny squirt of lemon juice as the US. The UR was salivation Tested for generalization by changing the CS from URN (used for conditioning) to either EARN or VASE. Found much more salivation to VASE than EARN Only humans understand the semantic relation between URN & VASE, and thus results argue that the O is required between S + R Comparing classical & operant conditioning Classical Conditioning Operant Conditioning Nature of Response Reinforcement Involuntary, reflex Spontaneous, voluntary Occurs before response (CS & UCS are paired) Occurs after response Role of Learner Passive Active Nature of Learning Neutral S becomes CS Prob. responding is by assoc. w. US changed by its effect Types of Associative Learning Connecting two stimuli: Classical conditioning Stimulus 1: Lightning + Stimulus 2: Thunder Connecting a response to its consequences: Operant conditioning Response: Push button on vending machine + Consequence: Receive a candy bar Comparing classical & operant conditioning Learning Objectives 1948 1971 Define learning, and identify two forms of learning. Define classical conditioning and behaviorism, and describe the basic components of classical conditioning. Describe the timing requirements for the initial learning of a stimulus-response relationship. Summarize the processes of extinction, spontaneous recovery, generalization, and discrimination. Discuss the survival value of generalization and discrimination. Discuss the importance of cognitive processes in classical conditioning. Describe some of the ways that biological predispositions can affect learning by classical conditioning. Summarize Pavlov’s contribution to our understanding of learning. Describe some uses of classical conditioning to improve human health and well-being. Identify the two major characteristics that distinguish classical conditioning from operant conditioning. State Thorndike’s law of effect, and explain its connection to Skinner’s research on operant conditioning. Describe the shaping procedure, and explain how it can increase our understanding of what animals and babies can discriminate. Compare positive and negative reinforcement, and give one example each of a primary reinforcer, a conditioned reinforcer, an immediate reinforcer, and a delayed reinforcer. Discuss the strengths and weaknesses of continuous and partial (intermittent) reinforcement schedules, and identify four schedules of partial reinforcement. Learning Objectives cnt Discuss the ways negative punishment, positive punishment, and negative reinforcement differ, and list some drawbacks of punishment as a behaviourcontrol technique. Explain how latent learning and the effect of external rewards demonstrate that cognitive processing is an important part of learning. Explain how biological predispositions place limits on what can be achieved through operant conditioning. Describe the controversy over Skinner’s views of human Behaviour. Describe some ways to apply operant conditioning principles at school, in sports, at work, and at home. Identify the major similarities and differences between classical and operant conditioning. Describe the process of observational learning, and explain the importance of the discovery of mirror neurons. Describe Bandura’s findings on what determines whether we will imitate a model. Discuss the impact of prosocial modelling. Explain why correlations cannot prove that watching violent TV causes violent Behaviour, and cite some experimental evidence that helps demonstrate a cause55 effect link. SA Questions • Define the following classical condition acronyms: US, UR, CS & CR • Define precisely what is (needs to be) learned in classical conditioning and in operant conditioning. • What is meant by shaping? • What is the difference between shaping and operant conditioning? • What is spontaneous recovery? • At the level of the synapse, how might learning be represented? • What is latent learning? • What defines something as reinforcement or punishment? • Give a specific example of positive punishment and negative punishment. • Give a specific example of positive reinforcement and negative reinforcement. • Which schedule(s) of reinforcement tend(s) to produce the highest level of responding?