Lecture 8: Discrimination, Generalization, and Fading

Notes about Behaviour

• Behaviour is valuable only at the right time and appropriate situation

  —> Behaviours = context-dependent

• Successful behaviour change depends on teaching/learning when and where a behaviour is appropriate

ABC Assessment

• Antecedent

• Behaviour

• Consequence

Antecedent

Events or interactions that happen before the behaviour occurs

Behaviour

Behaviour or sequence which has occurred

Consequence

Events or interactions which happen after the behaviour

Stimuli =

people, objects, and events currently present in immediate

surroundings that activate sense receptors and that can affect behaviour

• Any stimulus can be an antecedent or a consequence of a behaviour

• These can become cues

Operant behaviour is

always influenced by the environment, including people, places, objects, etc.

Stimulus Discrimination Learning and Stimulus Control

• How do we learn to perform certain behaviours at certain times but not others?

• Always cues around when a behaviour is reinforced or extinguished à signal when reinforcement is available or no longer provided

Stimulus Control

• degree of correlation between a stimulus and subsequent response

• Good or Effective stimulus control = High correlation

Types of Controlling Stimuli

• S^D - Discriminative Stimulus

• S^Δ - Extinction Stimulus

• A stimulus may be simultaneously an S^D for one response and an S^Δ for another

S^D-Discriminative Stimulus

• Response has been reinforced only in the presence of a particular stimulus

• Cue that a particular response will pay off

S^Δ- Extinciton Stimulus

• Response has been extinguished only in the presence of a particular stimulus

• Cue that a particular response will not pay off

Stimulus Discrimination

Process by which we learn to emit a specific behaviour in the presence of some stimuli and not in the presence of other stimuli

Operant Stimulus Discrimination Training

Procedure of reinforcing a response in the presence of an SD and extinguishing that response in the presence of an S∆ —> Effects: stimulus discrimination, good stimulus control

Stimulus Generalization

• Responding the same way to a different stimulus

• Opposite of stimulus discrimination

Unlearned stimulus generalization due to considerable physical similarity

• Likely to perform a behaviour in a new situation if that situation is very similar to situation when behaviour was learned

Learned stimulus generalization involving minimal physical similarity

• Have to learn the stimulus class, or concept

• Common-element stimulus class

  • Set of stimuli, all of which have some physical characteristic in common

  • Conceptual behaviour – emitting appropriate behaviour to all members of a common-element stimulus class, but not those that don't belong to the class

Learned stimulus generalization despite no physical similarity

Stimulus equivalence class is a set of completely dissimilar stimuli which an individual has learned to group or match together or respond to in the same way.

Enduring Effectiveness of Stimulus Discrimination Training

1. Choose distinct signals

   • different along more than 1 dimension

   • stimulus only occurs when response should

   • grabs attention

2. Minimize opportunities for error

3. Maximize the number of trials

4. Make use of rules: describe contingencies

Contingency =

if then arrangement

Two-term contingency =

Behaviour- Consequence

Three term contingency =

As and Cs of a B

Contingency shaped behaviour =

developed through trial and error

Rule Governed behaviour =

controlled by the statement of the rule

Rule:

describes a situation in which a behaviour will lead to a consequence

Guidelines for Effective Stimulus Discrimination Training

1. Choose distinct stimuli - S^Ds and at least one S^∆

2. Select an appropriate reinforcer

3. Develop the discrimination

   • Arrange for several reinforced responses in the presence of the S^D

     • Specify rule (S^D —> desirable response à reinforcer)

   • When the S^Δ is presented, make the change from the S^D very obvious

4. Wean individual from the program

   • Perform schedule thinning and plan natural reinforcers

   • Plan periodic assessments of behaviour to make sure it is occasionally being reinforced and that the desired frequency of the behaviour is being maintained in the presence of the S^D

Fading

• Gradual change over successive trials of an antecedent stimulus that controls a response so that the response eventually occurs to a partially changed or completely new stimulus

• Process of slowly removing prompts after behaviour is established

• Reinforce appropriate responses

Dimensions of Stimuli For Fading

• Fading occurs along dimensions of stimuli

• Dimension – any characteristic of the stimulus that can be measured on some continuum

• Fading can occur across specific stimulus dimensions and across changes in general situation or setting

  • Ex: physical structure of room; number of other people present

Factors Influencing the Effectiveness of Fading

1. Choosing the final target stimulus =Stimulus that we want to evoke /produce the behaviour at the end of the fading procedure

2. Choosing the starting stimulus and prompt

3. Choosing the fading steps

1. Choosing the final target stimulus =Stimulus that we want to evoke /produce the behaviour at the end of the fading procedure (Factors influencing the effectiveness of fading)

Important to select a stimulus that will maintain responding in natural environment

2. Choosing the starting stimulus and prompt

• Prompt: a supplemental antecedent stimulus provided to increase the likelihood that a desired behaviour will occur, but that is not the final target stimulus to control that behaviour.

• Instructor behaviour as prompts:

  • Physical prompts/physical guidance - touching the learner to guide them appropriately

  • Gestural prompts - pointing, making motions without touching, etc.

  • Modeling prompts - demonstrating correct behaviour

  • Verbal prompts - verbal hints or cues

• Environmental alterations as prompts:

  • Altering the physical environment to evoke desired response

• Extra-stimulus vs within-stimulus prompts

  • Extra-stimulus – something that is added

  • Within-stimulus – alterations to the SD or S∆ to make them more noticeable and easier to discriminate

3. Choosing the fading steps

• Should be chosen carefully

• Need to monitor performance to determine the speed of fading

• If student begins making errors, prompts may have been faded too quickly or with too few steps

  • May need to backtrack

• If too many steps introduced or too many prompts provided, learner might become overly dependent on them

Extra stimulus =

something that is added

Within stimulus

alterations to the SD or S∆ to make them more noticeable and easier to discriminate

Gesture prompts =

pointing, making motions without touching, etc.

Modeling prompts =

demonstrating correct behaviour

Verbal Prompts =

verbal hints ot cues

Guidelines for Effective Application of Fading

1.Choose final desired stimulus.

2. Set an appropriate reinforcer.

3. Choose the starting stimulus and fading steps:

a) Specify clearly the conditions under which the desired behaviour now occurs.

b) Specify specific prompts that will evoke the desired behaviour.

c) Specify clearly the dimensions that you will fade to reach the final target stimulus control.

d) Outline the specific fading steps to be followed and the rules for moving from one step to

the next.

4. Put the plan into effect:

a) Present the starting stimulus and reinforce the correct behavior.

b) Across trials, the fading of cues should be so gradual that there are as few errors as

possible. However, if an error occurs, move back to the previous step for several trials

and provide additional prompts.

c) When control by the final target stimulus is obtained, wean the learner from the program.