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Lecture 5

PSYB45H3 Lecture Notes - Lecture 5: Classical Conditioning, Stimulus Control, Reinforcement

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Jessica Dere

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Lec05: Fading & Behavioral Chaining
Stimulus Discrimination Training vs. Fading
Both are focused on establishing appropriate stimulus
control over a certain behavior, given that the target
behavior already occurs at least occasionally
Fading can be used for errorless discrimination
training, shifting the stimulus discrimination with no
(or few) errors
Advantages over trial and error procedures:
oErrors consume time
oOnce an error occurs, it tends to re-occur many
oExtinction (lack of reinforcement) can produce
undesirable emotional reactions
Fading can occur along di'erent dimensions of stimuli
oE.g., volume of speech, content of speech,
physical cues, environmental cues, etc.
Implementing Fading E'ectively
Careful consideration of the *nal desired stimulus
oThe stimulus that you are aiming for at the end
of the fading procedure
oNeed to consider reinforcement in the natural
Choosing the starting stimulus: A prompt
oA stimulus that reliably evokes the target
behaviour, to help start the fading procedure
o Di'erent types of prompts exist
Teacher behavior as prompts
Environmental alterations as prompts
Extra-stimulus vs. within-stimulus prompts
: adding something to the
enviornemtn to help promote the behavior
: alterations to the SD or S∆ to
make them more noticeable
Need to ensure that fading is not done either too
quickly or too slowly
Have a speci*c plan for the steps to be taken in the
fading procedure
Need to monitor performance to determine optimal
speed of fading
oErrors may signal that the fading was done too
quickly, and you should backtrack to previous
Shaping vs. fading
BOTH are procedure of gradual change
oFADING: involves gradual change of a stimulus
oSHAPING: involves gradual change of a response
Behavioral chaining
Behavioral chaining:
oA sequence of stimuli and responses that occur
closely to each other in time, with the last
response followed by a reinforcers
oA sequence of discriminative stimuli and
responses where each response (except the last)
produces the SD for the next response, and the
last response is followed by a reinforcers
In a behavioural chain, each SD is:
oA cue for the next response
oA conditioned reinforcer for the previous
response (other that the *rst SD)
S+ = Reinforcer at the end of the chain
Stimulus response chain
oIf any response is not produced by the SD before
it, the chain is broken
Teaching a Behavioral chain
Three methods for teaching a behavioural chain
oTotal-task presentation
oBackward chaining
oForward chaining
Total-task presentation
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