Chapter 6: Learning 1 Learning 1. In perception we studied that we are responsive to stimuli in the external world. Although some of these stimulus-response associations are innate many are learnt. 2. Learning tells us that the chocolate in hand is sweet, it is a bad idea not to play pool before an exam, drive slow in residential zones etc. 3. So what is learning? Learning we can say then is an adjustment of our behaviors and beliefs based on past experiences. 2 Learning: Problems 4. The way we defined learning is rather coarse and does not account for a number of other things that also entail learning: a. Skills (learning to dance). b. Acquisition (learning the unknown). c. Simple associations (learning to associate smoke with fire). d. Ideas and Beliefs (learning how geometric solution to puzzles are derived, or how to behave in an interracial gathering). 3 1
Learning: Problems 5. We will look at these kinds of learning, beginning with simple forms of learning. 6. Simple learning forms become the basis of more complicated forms of learning. 7. They are intimately linked with our emotional and motivational behaviors. 8. Study of learning is not only important to understand how we behave but also how animals behave for there is so much that we share with other animal species. 4 The Perspective of Learning Theory 5 Aristotle 1. A thought (or an idea) that was originally experienced along with other thoughts, will on their recurrence will lead to the recall of the associated thoughts. 2. Laws of Association a. Similarity (lemon-lime) b. Contrast (night-day) c. Contiguity (table-chair) (384-322 BC) 6 www.martinfrost.ws 2
Law of Association 7 The Associationists 1. What mechanisms are responsible for the complexity of learning? 2. Associationists like Locke (1632-1702) and Berkeley (1685-1753) suggested that we learn by associating one idea with another. 3. The word flower with the smell and sight of a flower will form an association. For more complex learning more associations are incorporated. 8 Habituation 9 3
Habituation 1. Habituation is decline in organism s response to a stimulus once it becomes familiar. 2. Habituation ensures we attend to novel stimuli more closely than familiar (safe?) stimuli. It is simplest form of learning 3. Dishabituation is becoming sensitive to any change in the stimulus to which one has previously habituated (also called sensitization. Sensitization is revealed after habituation). 10 Classical Conditioning 11 Classical Conditioning 1. To study associations between stimulus and response perhaps that most investigated area has been classical conditioning. 2. Classical conditioning is another form of simple learning and was studied extensively by Ivan Pavlov. Pavlov (1849-1936) investigated cues (stimulus) that elicited salivation (response) in dogs and how they learned the cues to respond. 12 4
Experimental Setup Nobel Prize Seal 13 Classical Conditioning: Procedure 14 Classical Conditioning: Clip http://www.youtube.com/watch?v=cpolxen54ho 15 5
Classical Conditioning: Phenomena 1. Conditioned stimulus (CS) originally a neutral stimulus when paired with an unconditioned stimulus (US) and followed by an unconditioned response (UR) sets the stage for classical conditioning. 2. After many such presentations, CS alone elicits the CR. CR can be maintained if CS if reinforced by US. 16 Classical Conditioning: Phenomena 3. The optimal (best) time between the presentation of a CS and a US is one half second. This time produces the strongest conditioned response. 17 Classical Conditioning: Phenomena 4. If the CS is presented by itself without the US it will eventually fails to elicit the CR and extinction occurs. 5. Second-order conditioning: When a second CS is paired with the first CS; the second CS can also elicit the CR. 18 6
Classical Conditioning: Phenomena 6. Generalization: CS that resemble each other (even if never paired with the US) can elicit the CR. However there is a gradient of CSs. 7. Discrimination: Animal s ability to make fine discriminations between CSs, in terms of what will and what won t elicit the CR. 19 US-CS Relationship Strong conditioning Weak/No conditioning 20 Operant Conditioning 21 7
Instrumental Conditioning Also called Operant Learning Thorndike: Law of Effect First formal examination of instrumental conditioning Experimental set-up: The Puzzle Box The strength of a response is adjusted according to that response s consequences (Fig. 6.11) 22 B.F. Skinner and Operant Behavior Skinner (1940s): sharply distinguished between classical and operant conditioning Examined voluntary responses operant responses Contrasted with animals behavior in classical conditioning, in which behavior is elicited rather than chosen by the animal 23 24 8
25 26 Major phenomena of instrumental conditioning Discriminative Stimuli When will a behavior result in the desired outcome? When will it fail to result in the desired outcome? Control over outcome still an important factor in learning for organisms Animals are capable of more sophisticated discriminatory behaviors than is generally appreciated 27 9
28 Shaping Successive approximations: we shape the animal to do a difficult or complex task Begin with simple tasks Begin with first step of many Example: eating with silverware; riding a bike; any complex behavior 29 Reinforcers Primary reinforcer: food, water, escape, rest Conditioned reinforcer: predicts or helps create conditions that increase availability of primary reinforcers Defined after we see what patterns of behavior accompany its presence Not all events or responses are reinforcing under all conditions/lots of variability 30 10
Schedules of Reinforcement Partial reinforcement schedule: behavior is reinforced only some of the time Fixed reinforcement schedule: behavior is reinforced some of the time according to a fixed, predictable schedule Variable reinforcement schedule: behavior is reinforced some of the time according to an average number of reinforcements over time 31 Ratio and Interval schedules of reinforcement Ratio: based on the NUMBER of behaviors that have occurred Each n th behavior is reinforced: each 10 th, or each 4 th, or each 20 th, etc. (regardless of how much time has elapsed between behaviors Interval: based on the AMOUNT OF TIME that has elapsed since the last reinforced behavior Every ten minutes, reinforcement occurs for the next behavior (regardless of how many behaviors were produced during that ten minutes) 32 Fixed Ratio Schedule First, every response is reinforced Then, every 2 nd response is reinforced for a while If built gradually, very high ratios schedules of reinforcement can be built 33 11
Variable Ratio Schedule Reinforcement still comes after a certain number of responses Number of responses between reinforcement varies Reinforcement averages to every 5 th response, over a greater number of responses 34 Fixed Interval (FI) and Variable Interval (VI) Schedules FI: Example: checking the mail No matter how many times you check, the reinforcement (mail delivery) occurs on a fixed interval schedule: one time every day VI: Example: cat hunting a bird will come back to the hunting grounds about every 24 hours or so Sometimes more often (twice in one day), sometimes less often (once in two days), to maximize the chances of catching a bird 35 Punishment Not a reward, but rather some aversive event, follows one s behavior: shock, pain, loud noise More effective if strength/intensity of pain is high right from the first administration Trade-off: effective response suppression, but pay the price of cruelty/resentment from the person at the receiving end of the punishment 36 12
Change in behavior learning? Behavior changes in instrumental conditioning Is there an underlying change in insight? In comprehension? Tolman: demonstrated latent learning using an operant conditioning paradigm Rats explored a maze with no reward Later, under conditions of reward: could demonstrate formation of a cognitive map Indicated that learning had taken place, not mere conditioning 37 Act/outcome Representations Actions result in specific outcomes Mastery: satisfaction at having control over the outcome Two classic experimental findings: Infants and mobiles: infants like to make the mobiles move (Watson, 1967) (Fig. 6.16) Learned helplessness: control over environment lessens stress/distress; sense of futility, or lack of control, increases stress/distress (Seligman, 1975) 38 39 13
40 41 Varieties of Learning Taste aversion one-trial learning Prepared learning Biases exist to create associations between some events (illness is easily associated with particular food choices) but not other events Observational learning 42 14
43 The Neural Basis for Learning Learning processes are very similar across species For all species, learning depends on neural plasticity Capacity for neurons to change as a consequence of the experiences they have had 44 45 15
Neural plasticity Three types of change: Pre-synaptic mechanisms change Post-synaptic mechanisms change New synapses form Mechanisms: Long Term Potentiation (LTP) (Fig. 6.18) Activity dependent Growth of dendritic spines: new synaptic possibilities 46 Some Final Thoughts: Learning theory and beyond Lessons of learning mechanisms can easily be applied outside the laboratory Practical and useful ways of thinking about altering or maintaining behavior Connections to biological mechanisms: very important in their own right Connections to cognitive mechanisms: also needs to be understood to comprehend how we use what we have learned 47 Concept Quiz 1. According to learning theorists, most learning depends on the mechanism of: a. punishment. b. insight. c. association. d. reasoning. 48 16
Concept Quiz 2. Imagine a classical conditioning experiment in which you have participants suck on a lemon (which causes puckering and salivating) immediately after you touch the participant s arm. After many trials, the participants make a puckered face and salivate when you touch them on the arm. In this experiment, what is the unconditioned stimulus? a. the lemon b. puckering and salivating c. touching the arm d. the participant 49 Concept Quiz 3. What is the law of effect in instrumental conditioning? a. If a response is followed by a reward, that response will be strengthened. b. If two stimuli are presented at the same time, an association between the two will be created. c. If an individual (or animal) observes a behavior, that individual (or animal) is likely to imitate the behavior. d. There are biological constraints on which behaviors an individual (or animal) can learn. 50 Concept Quiz 4. The neural mechanism of learning that increases the responsiveness of a neuron is called: a. activation formation. b. long-term potentiation. c. action potential. d. cortical remapping. 51 17