Week 5 Flashcards
Classical vs Operant Conditioning
Classical Conditioning • Ivan Pavlov • Learning via association • (Lectures 2 + 3) Operant Conditioning • B.F. Skinner • Learning via reinforcement • (Lectures 4 + 5)
Theories of reinforcement
- The role of response and reinforcement
- Skinner
- Drive reduction
- Behaviour regulation (Premack)
Learning by doing?
• Thorndike thought that a response had to be performed and a consequence experienced for operant learning to occur • However, Tolman showed that this is not so – Responses: e.g. learning without doing (e.g. rats running a maze vs rats transported through maze, learned the same way) – Consequences: e.g. rats acquire a cognitive map of their environment even if not rewarded. So-called latent learning (Tolman & Honzik, 1930)
Expectations about the reinforcer
• Thorndike thought that learning involved the
pairing of Stimulus and Response – without
inclusion of the reinforcer
• Tolman argued that the reinforcer becomes part of
associative network (stimulus, response and
reinforcement)
– Animal develops expectation
• E.g. train monkey to perform action that leads to
banana, and then replace reward with lettuce ->
monkey surprised and frustrated
Experiment by DeWaal & Brosnan
Monkeys reject unequal pay
Theories of reinforcement:
Skinner’s operational definition
- Reinforcer increases rate of behaviour
* Punisher decreases rate of behaviour
Theories of reinforcement:
Drive reduction theory
Hull & Spence (1940s)
• 1st theory of motivation
• If homeostasis is disrupted drive is observed
– Primary drives are innate (e.g. thirst, hunger)
• Drive = unpleasant state that the animal wants to
reduce
• Drive reduction of physiological needs = negative
reinforcer & major cause of learning
But… not all reinforcers reduce a biological
drive
• Secondary reinforcers (e.g. money)
– Money can only indirectly reduce drive
– Bridging (previous lecture)
• Novel Stimuli – e.g. Sensation seeking
– Some reinforcement comes from raised
stimulation
– wild rats, mice and shrews elect to run
in wheels
– Working to get access to a window
• Pleasure seeking
• e.g. Intra-cranial reinforcers
Olds & Milner (1954)
Electrical stimulation as positive reinforcer
Intra-cranial Reinforcers
Rise of the ‘ratbots’?
- Talwar et al. (2002)
* Nature, 417, 37-38
What if…
• What if stimuli aren’t reinforcers – E.g., water isn’t a reinforcer • But behaviours are reinforcers – E.g., DRINKING is a reinforcer • Behavioural homoeostasis (not food, but eating is reinforcing) • “Bliss point” of behaviour
Theories of reinforcement:
Behaviour regulation
• Premack’s principle (1965)
– A high probability behaviour can reinforce a low
probability behaviour
▪ We have a hierarchy of behaviours arranged
according to response probabilities
(preferences)
The Premack Principle
More probable behaviours will reinforce less probable behaviours
Using Premack’s Principle
Brown, Spencer, & Swift (2002) saw a 7-year-old boy, who refused to eat all but a few specific foods • Low probability behaviour: eating new foods • High probability behaviour: eating favourite foods • At meal-times, parents told him if he ate a small amount of new food, he could have his favourites • Boy gradually began to eat his greens!
Avoidance vs. Escape
• Remember that punishment ideally involves no
possibility of avoidance/escape
• But, what if the animal has some control?
• Escape learning–emit a response that
terminates an aversive consequence (negative
reinforcement)
• Avoidance learning – emit a response to
prevent the occurrence of an aversive
consequence altogether
– but how can this be examined in a lab?
Present CS (light dims) followed by US (shock)
Initial trials feature escape, then avoidance takes over
Learning About Avoidance Learning
▪ Helps us to understand anxiety behaviours
▪ Phobias
▪ Often never encounter aversive event again
▪ How are phobias maintained?
