1.3 The Role of the Discriminative Stimulus in Behaviour

Question 1

How does extinction happen?

Answer 1

Availability of reinforcement is removed, leading to zero contingency between response and reinforcer

Established reponse tends to devline

Observed both in instrumental and classical conditioning

Question 2

What is theh partial reinforcement extinction effect?

Answer 2

Responding acquired with PRF persists when not reinforced to a greater extent than continuous reinforcement.

The less reliably a response is reinforced, the more persistent it is during extinction.

Question 3

Give an example of a study of a partial reinforcement extinction effect

Answer 3

Lewis & Duncan 1956

1. Poke machines set up in lab, participants played with fake money.
2. In initial phase participants were winning between 0 and 100% of the time. In later phase they all stopped winning
3. They could quit whenever they wanted to - experiementers measured how many times they play before they quit
4. Those reinforced less logged a higher number of plays before quitting than those who were continuously reinforced

Question 4

1. Differentiate the effects of S+ versus S-

2. Why may this view be too simplistic in some cases?

Answer 4

1. In the presence of S+ the response is reinforced
   In the presence of S- response is not reinforced
2. Respodning in presence of S+ may be sensitive to “value” of the reinforcement
   S+ and S- act to faciliatate and inhibit the R-Rft association

Question 5

Give a real life application of discriminative stimuli use

Answer 5

Therapy for autistic children

Question 6

What kind of discriminative stimuli are usually used in experiments?

Answer 6

Discrete - lights, tones, etc.

Question 7

What are some non-discrete discriminative stimuli?

Answer 7

Contexts, emotional or physiological states, the passage of time, the reinforcer itself

Question 8

Describe a study using non-discrete discriminative stimuli

Answer 8

Rat runway:

1. Rat does not know whether there is food at the end of runway
2. Food present only every other day
3. Measure how quickly it runs to the other side
4. Nothing in the context tells the rat whether there is food, EXCEPT what day it is being tested on
5. First they don’t discriminate between food and non-food days
6. Over time they learn to remember what happened the previous day – run faster through runway on food days

Question 9

Why does continuous reinforcement lead to faster extinction than partial reinforcement?

Answer 9

CRF and Extinction serve as distinguishable “markers”.

Extinciton is not as noticable to the subject if reinforced partially.

Question 10

What is the relationship between Response-Reinforcer and S+-Response?

Answer 10

A link between R and Rft diminishes, the link between S+ and R will also fade

Question 11

Under what circumstances do we see evidence for the original R-Rft association after extinction?

Answer 11

Spontaneous recovery
Reinstatement
Rapid re-acquisition
Renewal

Question 12

Why is context important in extinction?

Answer 12

Extinction as new learning:

Inhibitory learning may be specific to the context in which learning occurrs

Context can inhibit R-Rft relationship

Question 13

How is stimulus control acquired?

Answer 13

Through differential reinforcement.

Variations in reponse rate when the feature is manipulated (e.g. changing the colour of the stimulus)

Question 14

1. What is generalisation?

2. What is the opposite of generalisation?

Answer 14

1. If Rft is delivered in the presence of a stimulus (S+), learning tends to generalise to similar stimuli.
   This can be shown on a generalisation gradient and works for discrete stimuli as well.
2. Discrimination

Question 15

What are the consequences of stimulus discrimination?

Answer 15

Discriminating between stimuli leads to behaving differently towards them

Question 16

In what cases does discrimination apply?

Answer 16

1. The stimuli are easy to tell apart (but obviously different along some dimension like colour) — traffic lights
2. The stimuli are confusable and the difference between them is not obvious — finger prints

Question 17

What is discrimination learning?

Answer 17

Process by which we increase the discrimination between two stimuli

It can produce biases in generalization to other stimuli

Question 18

What is the difference between sensory limitation and lack of stimulus control?

Answer 18

Sensory limitation = organism cannot discriminate

Lack of stimulus control = organism doesn’t discriminate

Question 19

What is peak shift? Explain using pigeon example

Answer 19

Hanson (1957)

1. Pigeons given two stimuli with very little variation in colour
2. Control group only got S+
3. Experiment group given a difficult discrimination
4. Experimental group showed displacement of the “peak” (max. responding) of the gradient away from S+ in the direction opposite S-

Question 20

Explain how caricatures help us recognize faces

Answer 20

The average for a face is S-
S+ is something that should be specifc to someone distinctive
Caricatures exaggerate these S+ features and help us recognize faces quicker

Question 21

Explain the concept of categorization using Watanabe et al. 1995 study

Answer 21

Animals can learn to discriminate between complex stimuli, even on seemingly “conceptual” grounds – prototype learning

1. The study looked at whether they could train pigeons to dinstinguish between different artists and styles - showed them Monet’s work
2. Pigeons generalized what they learned to other impressionist artists, not just Monet

Question 22

How can prototype/category learning be explained?

Answer 22

It might be that animals learn about the features that category members share in common.
The most common features (like ‘leg’ shapes) are most strongly reinforced, become best discriminative stimuli
Features common to BOTH categories are not as strongly reinforced.