Chapter 8: Stimulus Control of Behaviour Flashcards
S+
Response and outcome
S-
response -> no outcome
Stimulus control
the degree to which an organism produces (or withholds) a response in the presence of a stimulus vs. its absence (or presence of other stimuli)
How to measure stimulus control
How do we “ask” animals (or human infants) if
two stimuli are different from one another?
– Differential responding
• Remember the habituation to visual patterns in infants?
– Stimulus discrimination: differential responding in the presence of two or more stimuli
Reynolds (1961)
– “What is the pigeon paying attention to?”
compound stimulis
peck differently
both pigeons respond differently
at no point were these pigeons explicitly trained to peck the site triangle or red circle
results here are purely by chance, but overshadowing could occur (classical conditioning) one element is more salient and thus can control behaviour to a stronger degree. Overshadowing seen in stimulus control in operant conditioning
less likely to learn about the less salient stimulus
Different stimulus elements controlled responding of different birds
Compound Stimuli & Overshadowing
• Some compounds show learning decrements for particular less-salient elements
Stimulus generalization
• Failure to discriminate between two similar
stimuli
– i.e., Baby Albert generalized his response
– Baby Albert did not discriminate between a white rat and a rabbit, a white mask, or a furry blanket
opp of stimulus discrimination
phobias develop like this
Stimulus generalization gradient
Guttman & Kalish (1956)
Pigeons trained to peck a
certain wavelength of light
– Food reward
“Probe” test with all different
wavelengths
– no reward
Gradient of responding is a function of how similar each test stimulus is to the training stimulus (Trained CS = light 530 nm, but Pigeons show CR (key pecking) to similar wavelengths of light)
most responding (the peak) when the colour is just right, also responding to similar colours = generalized responding to similar colours
- • The steeper the gradient, the more
stimulus control
What if there was no stimulus control?
• Then the animals would respond non-differentially
Sensory capacity
Stimulus control can ask questions about
what animals perceive
– Can an animal see colors?
• Train to discriminate between colours
– What is an animal’s sensory range?
• Train to discriminate between presence and absence of acoustic (or other) cue
Sensory capacity example
Japanese quail and European starlings trained
to discriminate between two different visual stimuli
people are trichromatic
birds are tetra
birds can see in UV spectrum
ask bird can you see the diff between these two lights if one has food and the other does not? Diff outcomes for responses made
just as good in UV and non UV light trials
therefore they can see UV light!
Not All Stimuli Are Discriminated Equally
• Some stimuli are more easily used as
discriminative stimuli than others
• Training songbirds to discriminate natural
stimuli goes more quickly than training synthetic stimuli
Degree of stimulus control also depends
on the type of reinforcement used. How?
Some stimuli work better when contingent with positive reinforcement, others with negative reinforcement • Foree and LoLordo (1973) tested this idea in pigeons
pigeons like visual cues associated with foods!
some work better with appetitive reinforcement, and others with aversive reinforcement
Foree & LoLordo (1973)
Type of Reinforcement
Training: • Group 1 – L/T … press pedal … food • Group 2 – L/T … press pedal … avoid shock
Group two more likely to press when the T is presented, than when the light is on
Group 1 respond just as much to the L as to the L and the T, and never respond when just the T is on
both outcomes are good, but the type of outcome drastically changes their responding
summary: Belongingness & behavioural systems – Food activated feeding system • Visual cues ‘go with’ food – Shock activated defensive system • Auditory cues ‘go with’ predators
Overshadowing
• Stimulus salience • Both ‘belongingness’ and intensity
Stimulus Discrimination Training
- Pavlov believed generalization was transfer of learning
- More recently accepted as lack of training (the more training you have, the better you are at discriminating between stimuli Cs+ or CS- or with S+ and S-).
Can have discrimination training in both
classical and instrumental conditioning
– Classical Conditioning: CS+ or CS-
– Instrumental Conditioning: S+ or S-
• Stimuli explicitly associated with other
stimuli or outcomes
first generalization, then discrimination
Errorless Discrimination Training
Faster, fewer errors by “fading in” S- over trials
early on S+ is more salient, early on more likely to respond to something obvious.
technique can be used in teaching children
builds confidence in children
higher reinforcement that there is less requirement for errors in learning
Training and Stimulus Control
Use generalization gradient to determine
degree of stimulus control
Need to determine the feature(s) of the
discrimination procedure that controls the
gradient
Jenkins & Harrison, 1962
• Stimulus control increased by discrimination
training
• If S+ and S- differ along a single stimulus dimension, then more control stimulus control can be gained
single modality
pitch of tones is diff
if a S- is trained, you see more stimulus control than the group that never gets trained with a S-
Spence’s Theory of Peak Shift
- Excitation develops around the S+
- Inhibition develops around the S-
- Peak-shift was the net effect of these two generalization gradients
Stimulus Generalization and Prejudice
Lack of Discrimination Training
• Miller (1948):
“Displacement” caused by discrimination + generalization
• “Mere Exposure Effect”
Phobias and other Anxiety Disorders
•Problems of stimulus generalization
•Fear-inducing scenario;
generalized anxiety to similar (but innocuous) situations
peak shift
The ‘peak shift’ effect is basically to do with how, when we’ve (I say we, most of the work is from non-human animals, but it is noted in humans too) learnt to be rewarded for one thing and not for a similar thing, we will respond more so something more different to the non-rewarded thing.
Pigeon Art Appreciation
- Watanabe et al. (1995)
- Trained pigeons to discriminate between Monet and Picasso
- Achieved high degree of accuracy
• Pigeons generalized to other artists of the same style (Impressionist or Cubist)
Pigeon Cancer Diagnosis
- Levenson et al. (2016)
- Trained pigeons to discriminate between mammograms with and without masses
- Achieved high degree of accuracy except on images that doctors struggle to diagnose
Categorization
• Discrimination of stimuli and transfer to
novel stimuli is indicative of categorization
• …or even concept learning
Concepts
• Abstract relations between categories, such
as “bigger”, “faster”, or simply “same as”
Stimulus Equivalence
- Explicit generalization training
* e.g., teaching relationships
Stimulus Equivalence Classes
Exhibit three properties:
• Reflexivity: A = A, B = B
• Symmetry: if A = B, then B = A
• Transitivity: if A = B and B = C, then A = C
• Importance of stimulus equivalence in language learning
Contextual Cues
• Not all discriminative stimuli are discrete or explicitly-presented • e.g., training animal in one box and testing in another • Think of ‘context-dependent learning’
Interoceptive Cues
• Stimuli that are internal to the animal also control behaviour • e.g., body states (hunger, arousal), internal sensation (drug process), or cognition (‘sense’ of time) • Think of ‘state-dependent learning’
Conditional Relations
- Discriminative stimuli set the occasion for responding
* Remember S(R-O) learning: the response-outcome relationship is conditional upon the correct stimulus
Modulation
• A cue that signals when a CS or response will end with a particular outcome modulates or facilitates the relationship (and thus responses)
Stimulus-Element Approach
• So far our focus has been on the individual
elements of compounds (light, tone) rather
than holistic compounds (light+tone)
Configural-Cue Approach
- Gestalt compounds
- Overshadowing results from different generalization decrements for elements
- ‘Pigeon art appreciation’ difficult to explain from individual elements
Positive/Negative Patterning
• Explicit compound-cue training
Sequence Discrimination
- Chaining and other complex stimulus/behaviour sequences
* Individual steps serve as S+ for next response
“Pigeons Rank-Order Responses to Temporally Sequential Stimuli”
- Same stimuli: discriminative component based on time/order
- S+ : red-green-blue
- S- : any other order
- More responses during reinforced order and to stimuli closer to blue
Stimulus Control in Daily Life
Studying, Sleeping • Avoid contexts (SD) that cue non-target behaviours
