PSYC2010: Brain and Behaviour

Transcription

1 PSYC2010: Brain and Behaviour PSYC2010 Notes Textbook used Week 1-3: Bouton, M.E. (2016). Learning and Behavior: A Contemporary Synthesis. 2nd Ed. Sinauer Week 4-6: Rieger, E. (Ed.) (2014) Abnormal Psychology: Leading researcher perspectives. Sydney: McGraw-Hill Education (3rdEdition). Free reading: 65c4-4d61-82fe-89956f Section 1: Learning and motivation Lecture 1: Fundamental concepts in the behavioural sciences Questions What is classical/pavlovian conditioning? What is instrumental and free operant learning? What is the difference between classical and instrumental learning? What do CS, US, CR, UR, Sd, Operant, Rf mean? What are the different types of reinforcement and punishment? What do S, R, O, S* mean? Behaviour Neuroscience is made sense in light of behaviour (i.e. examines the role of the brain) Experimental analysis of behaviour o Early behavioural research focused on the observable causes of behaviour: The contingencies between stimuli and responses that conditioned behaviour. o To recognise when someone is trying to change your behaviour. Classical/Pavlovian conditioning? Classical conditioning (Pavlovian conditioning): o Unconditioned stimulus (US) Food o Unconditioned response/reflex (UR) Salivate o Conditioned stimulus (CS) Bell o Conditioned response/reflex (CR) Salivate Instrumental and free operant learning? Instrumental learning: o Tripartite contingency (the ABC): Antecedent: The stimulus controlling behaviour à The Discriminitive Stimuli (Sd). Behaviour: What is the Response being reinforced à The operant: the precise aspect of the response that determined reinforcement 1

2 Consequence: What is the immediate outcome of a behaviour? à The Reinforcing Stimulus (Sr). Difference between classical and instrumental learning? Classical conditioning (Pavlovian conditioning): the subject has no control over events, but responds to them o Conditioned Stimulus (CS) à Unconditioned Stimulus (US) Instrumental learning: the subject has to respond to change the circumstance (The behaviour is instrumental in determining what happens) o Stimulus à Response à Outcome What do S, R, O, S* mean? Classical conditioning à S-S, S-S* or S-O learning Instrumental à R-O or R-S* Two process theories Two process theories: o Types Automatic/implicit i.e. low effort, rapid, default, no need working memory Controlled/explicit i.e. high effort, low capacity, slower, limited by working memory o Example in marketing Heineken à Beer (explicit association) Heineken à Buzz, fun, naughty (implicit association) [the brand becomes associated with these feelings 2

3 Lecture 2: (Instrumental learning) Positive reinforcement and extinction Bouton (2007) p 46-50, 60-63, Adaption in Instrumental Conditioning The Law of effect o In instrumental conditioning, we are always concerned with the relationship between a behaviour (R) and a biologically significant event or outcome (S*) o Instrumental learning generally works so that animals will maximize benefits (good S*) and minimize costs (bad S*) o Reward learning: a behaviour produces a good S* and thus the behaviour increases in strength Punishment: behaviour lead to S* that are bad or painful causing behaviour to decrease (note the bad S* is called punisher) Avoidance: when a behaviour prevents a bad S*, the behaviour increase in strength Escape: if a behaviour terminates a bad S*, the behaviour increases Omission: prevents the occurrence of a good S* causing the strength of behaviour to decrease (i.e. If I don't clean my room, my laptop gets taken away) Reinforcement: used to describe a situation in which a relation between an R and an S* increases the strength of a response o Skinner: believes that outcome has to be observed remove any subjective aspect thus reinforcing instead of satisfying o i.e. positive reinforcement (reward learning), negative reinforcement (avoidance or escape learning) Shaping: The process where by brand new behaviour added to an animals repertoire 3

4 o i.e. in the Skinner box getting the rat to press the leaver for a food reward (the trick is to reinforce closer and closer approximation of the lever press response) o To be effective, behaviour shaping must adhere to the basic principles of reinforcement: Close temporal continuity between R and Rft Avoid giving the random reinforcement (this degrades the contingency) Avoid reinforcing the wrong behaviour o Response chaining (apply shaping to more complex behaviour): Response chaining involves shaping a sequence of responses (working backwards) Conditioned reinforcement or Secondary reinforcer Conditioned reinforcer: Previously neutral stimuli that may acquire reinforcing properties o Conditioned reinforcers acquire their value through classical conditioning from their primary reinforcer i.e. money, clicker training in animal o Behaviour chain: Binding complex sequence together The behaviours in the chain are glued together by discriminative stimuli which are present at each step which has 2 roles: to set the occasion for the next response and reinforce the preceding one i.e. pressing the lever brings the click which reinforces it and then sets the occasion for approaching the food cup Primary reinforcer: stimuli or events that reinforce because of their intrinsic properties i.e. food, water, sex Factor affecting instrumental conditioning 1. Temporal continuity: (time between response and reinforcer) o General rule: the closer two event occur together, the more likely the animal will behave as if the two event were associated i.e. in Instrumental learning when R proceeds immediately by a S* i.e. in classical conditioning, the animal will respond more to S if S has preceded S* by only a short delay o With the exception to conditioned taste aversion 2. Contingency: (a future event or circumstance which is possible but cannot be predicted with certainty) 4

5 Schedules of reinforcement Continuous reinforcement schedule (CRF): when a behaviour is reinforced every time it occurs Partially reinforcement o Produces slower but more persistent responding (even during extinction) Ratio schedule: reinforcer delivered after a certain number of responses o Fix ratio (FR) schedule: reward is schedule after ever xth response o Variable ratio (VR) schedule: the number of response required to earn each individual reinforcer varies i.e. on a VR 4 schedule, the average number of responses required to earn a reinforcer is 4, but the first pellet might be delivered after 2 response, the second after 6 and so forth 5

6 Overall this generates less post-reinforcement pausing Interval schedules: reinforcers are delivered for the first response made after a certain interval of time has elapsed o Fixed Interval (FI) schedule: interval remains constant from one reinforcer to the next Scalloping : the animal learns to time the interval and the elapsed time become a sort of discriminative stimuli for responding o Variable interval (VI): There is an average interval after which the first response is reinforced, but each reinforcer is set up after different intervals Since time becomes less relevant in predicting reinforcer availability, VI schedules do not produce as much scalloping as FI schedules, instead, they tend to generate very steady rates of behaviour Extinction Extinction: behaviour is lost because of direct experience with R or S now disconnected from S* o In either instrumental or classical conditioning, responding remains high as long as R or S continues to produce or predicts S*. However if S* is dropped from the situation, responding will declaim o Useful in a clinical setting; Exposure therapy: in reducing learned fears (classically conditioned phobias and anxiety disorders) However, behaviour DOES NOT involve the destruction of the original learning: evidence for the original association re- emerges under some circumstances o Context plays a critical role in extinction as it to play a role in the discriminative stimulus i.e. context sometimes acts as a discriminative stimulus o Spontaneous recovery: an extinguished response can recover with the passage of time o Reinstatement: occurs when re-exposed to the US alone, after having undergone extinction. The effect is due to conditioning of the context, such that when the US is presented after extinction, an individual associates it with the original context o Rapid re-acquisition: the conditioned response can sometimes return very quickly when CS-Us paring are repeated after extinction o Renewal: The phenomenon in which a change of context after extinction can cause a robust return of conditioned responding Responding acquired with PRF persists when non-reinforced to a greater extent than CRF o The less reliably a response is reinforced, the more persistent it is during extinction 6

7 Lecture 3: (Instrumental learning) The role of the discriminative stimulus in behaviour Bouton (2007) p , , Discriminative stimuli Stimulus Control; o Mechanisms that allow us to learn to discriminate situations where behaviours are rewarded from situations where they are not o i.e. Skinner s rat pressing the lever in the presence of light (when the reponse was reinforced) and not pressing the lever in the absence of light (when the response was not reinforced) à The presence of light acted as the discriminative stimulus o Stimulus control was acquired through differential reinforcement Discriminative stimuli: a stimulus in the presence of which a particular response will be reinforced - to set the occasion for response rather than eliciting a response (i.e. toy in child behaviour) o S D (or S+) à In the presence of S D, the response is reinforced o S Δ (or S-) à In the presence of S Δ, response is not reinforced Stimulus control: Generalisation and discrimination Generalisation: if a reinforcement is delivered in the presence of a stimulus (S+), learning tends to generalise to similar stimulus i.e. pigeon learning to peck at new images with a tree in it o Generalisation as a failure to discriminate? Organisms cannot discriminate (sensory limitation) Organism doesn t discriminate (lack of stimulus control) Discrimination: behaving differently toward stimuli that are different o It applies to cases where; Stimuli are easy to tell apart (i.e. along different dimensions such as colour) 7