Download Conditioned Inhibition

Conditioned Inhibition
• Procedures for producing CI
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Conditional (standard) Procedure
Negative Contingency/Explicitly Unpaired
Differential Procedure
Backward Conditioning
Long-delay/Trace Conditioning
Procedures for Measuring CI
• Directed Behavior Test
• Summation (Compound Stimulus) Test
• Retardation-of-Acquisition Test
Chapter 4
• Classical Conditioning: Mechanisms
– What makes effective conditioned and
unconditioned stimuli?
– What determines the nature of the conditioned
response?
– How do conditioned and unconditioned stimuli
become associated?
What makes effective Conditioned
and Unconditioned Stimuli?
Initial responses to the stimuli
CS – does not elicit the CR initially
US – elicits the target response without any special training
Identification of CSs and USs is relative
A particular event may serve as a CS relative to one
stimulus and serve as a US relative to another stimulus
Saccharin – a tasty solution that rats like
Saccharin can serve as the CS in a taste-aversion
experiment where illness is the US
The same saccharin could serve as the US
L
Saccharin
The animal would approach the L
The Novelty of Conditioned
and Unconditioned Stimuli
The behavioral impact of a stimulus depends on its novelty
Familiar stimuli do not elicit as vigorous a response as do
novel stimuli (i.e., Habituation)
Stimulus novelty is important for classical conditioning
If the CS and/or the US are familiar, conditioning proceeds
more slowly than if they were novel
Testing the role of stimulus novelty involves 2 phases:
- preexposure
- conditioning
CS-preexposure effect or Latent Inhibition
Phase 1: Preexposure
Subjects are given repeated presentations of the CS alone
Phase 2: Conditioning
Subjects are given pairings of the CS with the US
The initial preexposure to the CS usually retards subsequent
conditioning
This latent inhibition effect is similar to habituation
- the repeated preexposure to the CS limits the
processing of, or attention to, the stimulus
US-preexposure effect
Experiments on the importance of US novelty are designed
in a similar way
Phase 1: Preexposure
Subjects are given repeated presentations of the US alone
Phase 2: Conditioning
Subjects are given pairings of the CS with the US
The initial preexposure to the US usually retards subsequent
conditioning
- may be due to conditioning of background cues
during the preexposure phase
CS and US Intensity and Salience
Stimulus salience – refers to the significance or
noticeability of the stimulus
Learning occurs more rapidly with more salient, or more
noticeable, stimuli
A stimulus can be made more salient by increasing the
intensity of the stimulus
-A more intense US will usually result in better
conditioning
-A more intense CS also results in better
conditioning
US Intensity
Flavor
LiCl
See bigger aversion in
the group that got the
high dose of LiCl (i.e.,
more intense US)
Cons
Low dose
High dose
CS Intensity
A more intense CS also results in better conditioning
This makes sense from an ecological point of view
- a more intense CS will be more salient than
the background and will command more attention
With CTA, a stronger concentration of flavor results
in bigger taste aversions
- the taste becomes more different than plain
drinking water
CS Intensity
Overshadowing
If two stimuli are presented together and followed
by a US, will see better conditioning to the stronger
of the two stimuli
TL
Shock
T = loud
L = weak
T better able to suppress barpressing
A stimulus can be made more salient by:
- increasing the intensity of the stimulus
- making it more relevant to the biological needs of the
animal (i.e., can increase the salience of a salt taste by
depriving the animal of salt)
- making laboratory CSs more similar to stimuli animals
might encounter in the natural environment (i.e., quail)
Rate of Classical Conditioning is also affected by:
CS-US Relevance, or Belongingness
- the extent to which the CS is relevant to, or belongs with,
the US
The importance of stimulus relevance was demonstrated
in an experiment by Garcia & Koelling (1966)
They compared learning about peripheral pain (footshock)
and learning about illness
In nature, rats are likely to get sick after eating poisonous
food, but experience peripheral pain after an encounter with
a predator
Garcia & Koelling’s (1966)
“bright and noisy water” experiment
Phase 2 (test)
Phase 1
Group 1: Sacc + LN
LiCl
½ Sacc
½ LN + water
Group 2: Sacc + LN
Shock
½ Sacc
½ LN + water
If taste and sickness ‘go together’, then group given LiCl should
have a bigger aversion to saccharin than to the audiovisual cue (LN)
Sacc
LN
Cons
LiCl
Shock
Rats that got poisoned decreased saccharin consumption
Rats that got shocked decreased consumption of the
‘bright and noisy’ water
This experiment suggests that tastes are more readily
associated with sickness than with shock (peripheral pain)
and that audiovisual cues (LN) are more readily associated
with pain/shock than with sickness
Selectivity of association
We see evidence of this selectivity of association in other
species
For ex., certain birds locate food by its visual characteristics,
rather than by its taste
Wilcoxin et al (1970)
Trained rats and quail
Taste + visual CS paired with poison
Train: Sour Blue
LiCl
Test: ½ blue water
½ sour water
Subjects given blue water were being tested for aversion to color
(visual property of food) while those given sour flavor were being
tested for taste aversion
Sour water
Blue water
Cons
Rats
Quail
Rats showed a strong aversion to the sour flavor and little
aversion to the visual properties of the food
But see opposite pattern in birds – strong aversion to blue
water but little aversion to the sour taste
The CS that is most easily conditioned is the one that
animals use to procure food
Rats use taste and odor cues to procure food
Birds use visual cues to procure food
The Concept of Biological Strength
Initially, the CS is weaker than the US
But after conditioning, the CS is strong and elicits
a vigorous response
Could the strong CS now serve as a US?
Higher-Order Conditioning
CS
T
US
Food
This is an example of first-order conditioning
The CS (Tone) will elicit salivation after a few trials
Now, pair
L
T
This is an example of second-order conditioning
The second CS (Light) will come to elicit salivation
Second-Order Conditioning
CS1
US
CR
CS2
CS1
CR
Money is an example of a powerful CS for humans
Similarity between Second-order conditioning
and the standard procedure for producing
Conditioned Inhibition
2nd order conditioning
CS1
US
CS2
CS1
CI
CS+
CS+/CS-
Important factors:
1. The number of no-US trials
- few no-US trials = 2nd order conditioning
- many no-US trials = CI
2. Pattern of trials
- 2nd order conditioning = sequential
- CI = interspersed
Examples of Classical Conditioning discussed so far satisfy
the criterion of differential biological strength
- strong US and weaker CS (1st order conditioning)
- strong CS1 and weaker CS2 (2nd order conditioning)
In some situations, associations form between stimuli when
this condition is not met:
1. Counterconditioning
Two stimuli become associated even though both elicit
strong responses
The normal response to the CS is reversed, or ‘countered’,
by pairing it with a US that elicits the opposite response
Shock
Food
2. Sensory Preconditioning
Two stimuli become associated even though both are weak
CS2
CS1
CS1
US
CR
CS2
CR
Because both stimuli are biologically weak in the first stage,
there is no robust response to measure
Sensory Preconditioning
T
L
(No CR to measure)
L
Food
(L elicits salivation)
T
(T now elicits salivation)
The procedure for Sensory preconditioning is very similar to
the procedure for 2nd order conditioning
- the 2 phases of conditioning are reversed
Sensory preconditioning
2nd order conditioning
CS2
CS1
CS1
US
CS1
US
CS2
CS1