Week 3 Flashcards
Blocking
Blocking = slower learning
(of association between the neutral stimulus and the US)
When a neutral stimulus and an excitatory stimulus
(CS+) together are paired with the US
Blocking- demonstrated by Kamin
Rats divided into 2 groups
control group:
Phase 1: rats saw both a light and heard a noise and then got shocked. Repeat
until rats developed a CR
Phase 2: Kamin then tested whether the rat reacted to just the light by trying to avoid being shocked. YES!
Blocking group: phase 1a:
rats heard a noise and then got shocked until they developed a CR phase 1b:
rats then heard the noise and saw the light and then got shocked
Phase 2: Kamin then tested whether the rat reacted to just the light by trying to avoid being shocked. NO!
Rats in both the blocking and control groups had seen the light and then been shocked exactly as
many times
• However, the rats
reacted differently
The Blocking Effect &
Hidden Assumptions
§ Any stimulus can be paired with any response (equipotentiality) § The more two stimuli are paired, the stronger the individual will associate them (contiguity) § Pairing the light with the shock didn’t lead to conditioning § The control group and blocking group had the noise+light/shock pair the exact same amount of times
Superconditioning
Superconditioning= faster learning
(of association between the neutral stimulus and the US)
When a neutral stimulus and an inhibitory stimulus (CS-)
together are paired with the US
Superconditioning- Rescorla
Phase 1: a tone was played in the
absence of a shock – tone became cue of
safety (Inhibitor)
Phase 2: a tone & a light presented together, followed by a shock
Phase 3 (test): Finally rats were
presented the light alone – rats in this
group showed stronger conditioning to
the light than rats in a control group that
did not go through phase 1
Blocking and Superconditioning
- Is paring of CS and US sufficient for learning?
No, surprise is necessry for learning
Free Energy Principle
• Global theory about how the brain works
• Tries to provide a unified account of action, perception and learning for adaptive systems
• The free-energy principle
– “any self organizing system that is at equilibrium with its environment must minimize its free energy”.
– “A formulation of how adaptive systems (that is,
biological agents, like brains) resist a natural tendency
to disorder.”
• Biological systems must maintain their states
despite a constantly changing environment (both
external and internal)
• The physiological and sensory states in which an organism can be is limited - low entropy
• Entropy = surprise. a “fish out of water” has high entropy
• Biological agents must minimize the long-term
average of surprise to keep sensory entropy low.
Classical conditioning phenomena..cont’d:
CS pre-exposure (latent inhibition)
• Does CS pre-exposure affect conditioning?
Yes, eg. pre-exposed to CS1-yellow light, then CS2- blue light and compering acquisition to CS1- yellow light
CS pre-exposure
slows subsequent conditioning for that CS compared to a new stimulus
What causes CS pre-exposure effects?
Possible Explanations
§Habituation
§Conditioned inhibition
Is CS pre-exposure due to habituation?
No §Context specificity §CS pre-exposure is context specific §Habituation is not context specific (it occurs regardless of the context)
Is CS pre-exposure due to conditioned inhibition –
Retardation test
• Must pass retardation & summation tests • Retardation test – Test: • Group 1:Pre-exposed to CS1 • Group 2: Pre-exposed to different CS2 • Compare acquisition to CS1 • CS pre-exposure retards (slows) learning
Is CS pre-exposure due to conditioned inhibition? –
Summation Test
No
When paired with an excitatory stimulus (E), a pre-exposed stimulus (I;
right red bar) reduces responding less than a true inhibitor (I; left red
bar). CS pre-exposure fails the summation test!
Conditioning phenomena- Condition inhibition
Passes both summation and retardation test
Conditioning phenomena- CS pre-exposure/Latent inhibition
Does not pass summation test, only retardation test
More classical conditioning phenomena:
Generalisation-Discrimination
§Does classical conditioning generalise?
§ Test:
§Train with CS1-US
§Test different groups with: CS1, CS2, CS3 …
§Most generalisation to similar stimuli
Example generalisation
Little Albert
Moore (1972) experiment
Rabbit’s eyeblink response • 16 rabbits • US: Mild electric shock • UR: Eye blink • CS+: 1200 Hz tone • Test stimuli during extinction: – 400Hz, 800Hz, 1200Hz, 1600Hz, 2000Hz.
Discrimination
Does generalisation last?
Not after extensive training trials
-Each exposure of CS1-US refines association
-Provided CS2 or CS3 not ever presented with US
-Reduced responding to CS2, CS3 … over time
Evolutionary benefits?
The basic principles
Generalisation
Discrimination
Generalisation
Other (similar) stimuli may also produce the CR
The more similar to the original CS, the more likely it is to elicit the CR
Discrimination
Early on during acquisition, generalisation maycause the learner to respond to a variety of stimuli
As learning continues, the organism learns which
CS seems to be best associated with US (they
discriminate)
The two parts to science
Research finds that trace conditioning is less
effective than short-delay conditioning
– Theory explains why trace conditioning is less
effective than short-delay conditioning
Models in psychology
A model
– is a formal attempt to explain a wide body of research
– Makes predictions
– Predictions can be tested
• Some models are mathematical: e.g. ∆V =αβ (λ−V)
Developing a Formal model of classical conditioning
Such a model should be independent of
conditioning procedure
§ It should generate testable predictions
§ Today: The Rescorla Wagner Model
§ Explains how organism learns the prediction of the US
What is the Rescorla-Wagner model?
The level of conditioning is a result of an internal comparison between:
§ Expected strength of the US
§ Actual strength of the US
§ Expectation is based on prior experience with the US (i.e., previous trials)
§ Strength of the US is fixed (e.g., mild shock)
what are the different parts to
The Rescorla-Wagner Model (1972)
∆V = αβ (λ −V)
λ – Magnitude of associative value that can be conditioned for CS; actual CS value
V - Current associative value of CS (expectations about the CS-US association/CSvalue)
Surprisingness of the US
∆V - Change in associative value of CS
α - salience of the CS
β - strength of the US to promote conditioning
Assumptions and the rescorla-wagner model
Previous models assumed that a CR gets
stronger the more a CS is paired with a US.
• Rescorla Wagner model basically assumes
that a CR gets stronger if the CS-US pair is
Rescorla-Wagner & the Blocking Effect
Kamin (1968) found that rats ignored a light if the light happened at the same time as a noise that they had previously learned predicted a shock. • This is the blocking effect. • violates the frequency principle • Rescorla-Wagner explain this by saying that the light doesn’t change how surprised the rat is at being shocked. • The rat ignores the light because it already expects the shock to happen because of the noise.
Rescorla-Wagner, & Superconditioning
• The Rescorla-Wagner model also predicted that there would be superconditioning (the opposite of blocking).
• Superconditioning occurs
when a previously learnt stimulus is combined with a new stimulus
• In superconditioning, the old stimulus is inhibitory and the combination is
excitatory -> surprise that US is presented!
• The organism develops an association between
the new stimulus & the
excitatory CS.
Attentional models of classical conditioning
- Rescorla-Wagner model is not Perfect…
- Has difficulty explaining/predicting CS Preexposure (Latent inhibition)
- Other models have been proposed to try and explain such phenomena
- Mackintosh (1975)
- Pearce and Hall (1980)
Taste Aversion
• In typical classical
conditioning, acquiring a CR requires dozens of trials
associating the CS and the US
• In typical classical
conditioning, long-delay
conditioning (more than a few seconds) is less effective
• Yet…
– You can acquire a taste aversion after one single association.
– The time between you eating the food and getting sick can be as long as 24 hours
• Of course, while it goes against the rules, it does so for good reason:
– It takes a while to feel sick after eating food
– And it’s really important to know which foods are bad to eat as quickly as possible
Some classical conditioning phenomena: Garcia effect (preparedness)
§Are all associations learned equally?
§ Equipotentiality: Every CS has the same potential to be associated with a US (Pavlov)
§Garcia & Koelling (1966) showed this assumption does not hold!
Some associations are learned faster than others!
Classical fear conditioning: contemporary research
Differential conditioning paradigm
fear-relevant: snake (CS+ excitory): snake (CS- inhibitory)
fear-irrelevant: mushroom (CS+ excitory): mushroom (CS- inhibitory)
Acquisition: a CS+ was paired
with a US shock; the other
type of stimulus was not paired with shock (CS-);
• Extinction: SCR (skin conductance response) was the CR.
Classical conditioning in everyday life: addiction
Many users die after taking a fairly usual dose in an unfamiliar environment
• Siegel et al. (1982) argued that this is because
the body’s tolerance to heroin is influenced by
classical conditioning
There are usually similar environmental cues
when is taken
• The endocrine system associates these cues with taking, and ramps up the tolerance response
• If those cues are not present, the body isn’t as prepared to tolerate heroin
• Overdose is more likely
Classical conditioning and addiction: ‘overdose’ experiment (Siegel et al., 1982)
§ Training: § Experimental: H in room A, Placebo in room B § Control: Placebo in both rooms § Test: Higher dose of heroin § Same: H in A §Different: H in B § Control: H §DV: Mortality §Same: 32.4% §Different: 64.3% §Control: 96.4% §Context conditioning affects tolerance
Classical conditioning in clinical settings
• If phobias are caused by classical conditioning…
• …you can use classical conditioning techniques to
eliminate or reduce them.
• How do you extinguish a CR?
• By presenting the CS without the US
• In clinical psychology, a program of presenting
the CS without the US is called systematic desensitisation
• Phobias persist because:
– people avoid situations where they see the phobic object (avoid opportunities to extinguish fear)
– They can be self-sustaining – e.g., trying to overcome
a fear of crowds can leave you feeling very embarrassed
• Systematic desensitisation gradually exposes the client to the phobic object in a gradual way
1. A fear hierarchy is constructed
2. Participant is given relaxation training
3. Psychologist gradually exposes the client to things higher on the fear hierarchy as they relax
E.g., after 3.5 years, 60% who were systematically
desensitised continued to fly (see Choy et al., 2007 for review)
