L13 -Latent Inhibition Flashcards
What is inhibitory learning?
Thought to require an expectancy of the US. It is this error that produces learning.
Therefore nothing should be learned when CS is presented without US before conditioning (there is nothing to learn about)
Latent inhibition
Learning in the absence of any consequences, which regards later learning about the same stimulus.
The pre-exposures stimulus had made it familiar which means it takes longer to learn about (slows down subsequent learning).
CS loses salience (is ignored) as subject learns it signals nothing.
Lubow Latent Inhibition Experiment
Study on Sheep and Goats
Animal exposed to conditioned stimulus,
1: light
2: fan
- First goat will experience one of the stimuli with no consequence
- During training it would experience a minor foot shock
- Takes more trial for the animal to learn when it is pre-exposed as apposed to novel
Westbrook Experiment
Pairing shocking rats with a stimulus
Learns pairing faster if it is not pre exposed
Why can’t the R-W model explain latent inhibition?
Because there will be no error, as during pre exposure:
Lambda = 0 (no US)
Sigma V = 0 (no expectation)
Therefore the error term = (0 - 0), so no learning
FAILS TO ACCOUNT FOR LATENT LEARNING
Bouton
Looks into the similarities of latent inhibition and extinction.
LI is procedural flipside of extinction
LI CS- then CS+US
Extinction CS+US then C-
Both failures to retrieve CS-US memory due to interference from CS-nothing memory
Less response to CS because of LI and extinction.
Westbrook et al: Context Specificity of latent inhibition
3 groups: Control, context consistent and context inconsistent, paired light to shock.
If LI is context specific, we would expect to see greater evidence of LI in consistent context group than inconsistent context group. So less learning as shown in the result.
It does take longer to learn association but it is not entirely context specific as some learning does still occur in inconsistent context group
Westbrook et al: LI overtime
2 groups: Pre-X and control with a stimulus and a shock
Test at day 1 and after 21 days to see association
Strong latent inhibition effect in PreX group after day 1
Loss of LI over time after 3 weeks
Implying that there is learning about CS shock, that isn’t being retrieved immediately, but is more likely to be retrieved if you wait a long time before testing
How is latent inhibition different from conditioned inhibition?
Only conditioned inhibition involves a cs that signals the reduction in the likelihood of US, neg contingency between cs and us, negative prediction error
Rescorla:
LI fails the summation test.
A Pre-X does not reduce responding to an excitatory CS
How does Wagner attempt to reconcile model to fit with LI?
- He attempts to reconcile with the pre-exposure effect adaptation
- He suggested maybe also learning is proportional to the amount the CS is surprising
- Conditioning does not proceed unless both US and CS are surprising
How does Wagners adaption impact the R-W model?
Take alpha term and modulate it depending on how surprising it is.
- When CS is unpredicted by context it has high alpha, as it reduces alpha reduces and learning is slower - Predicts retardation test, you will eventually get to asymptote just takes longer
DeltaV = LambdaCS - SUMVcontext) X B X (LambdaUS - SUMVCS)
LI is therefore context specific
Why do LI experiments often fail on humans?
Participants tend to be suspicious during Pre-X
If they notice it to be important it may override LI effects
Common way to solve human suspicion problem. Lubow Ginton Urca
Masking task:
- This means masking the reasons why it is being presented, an excuse as to why they will see it so they don’t create their own hypothesis
CS = burst of white noise, presented to participants as a distractor stimulus while completing an unrelated auditory task - masked CS pre-exposure
- However evidence to suggest this isn’t the same, as could be argued that you are training to ignore it
How is latent inhibition demonstrated in humans?
It affects people differently under different psych conditions
Latent inhibition absent or weaker in people with schizophrenia than in healthy individuals.
In particular, linked between reduced LI and positive symptoms of schiz e.g. formations and delusions
Those with schizophrenia have less control over their attention, so latent inhibition has been applied to try to understand what is occurring.
Links between schizotypy and reduced LI
Personality trait that varies amongst healthy individuals - schizotypy, sort of like your willingness to entertain unusual causal relationships, e.g. ability to control future events
High schizotypy reduced LI
