Yas- CM2

Blocking

Reminder of Blocking:
- Initial learning phase: A+ (Stimulus A followed by a US)
- Blocking phase: AB+ (Stimuli A and B together, followed by a US)
- Test: Present B alone. The typical finding is that there's little to no learning about B.
Prediction Error: Rescorla-Wagner Model
- Explains blocking by stating that the US is already predicted by A during the AB+ trials.
- Since there's no surprise (no prediction error), no association is formed between B and the US.
Alternative 'Attentional' Account of Blocking
- Suggests that attention to cues (α) changes with learning.
- During AB+ trials, attention to A is high (because A already predicts the US), while attention to B is reduced. This reduced attention to B leads to less learning about B.

Task: Participants are presented with colored squares, some followed by an electric shock.
The task is to determine which colors predict the shock.
If two colors that individually predict shock are presented together, the participant receives a double shock.
Example trials:
- Orange -> Shock!
- Orange Purple -> Shock!
- Brown White -> Shock!
Test Phase: Participants are asked which colors will be followed by a shock if presented alone.
Standard Blocking Result: Brown > Purple (Brown is more likely to be associated with shock than Purple).

Blocking is often explained as a failure to form an associative link between Cue B and the US.
- Orange -> Shock!
- Purple (no link formed)

Design: A+ then AB+
By the end of A+ trials, A fully predicts the US. Therefore, there's no prediction error.
During AB+ trials, the US is not surprising because A is already predicting it. Thus, B is not processed, and no B-US association is learned.
Learning about B is 'blocked' by A.

Before blocking, it was believed that associations form simply by pairing stimuli (Hebbian learning).
Blocking demonstrates that learning isn't just about pairing.
It is central to contemporary learning theory.

Surprise is the difference between what you predict will happen and what actually happens.
Rescorla-Wagner Model (1972)
ΔV = α(λ – ΣV)
- ΔV = Learning: Change in associative strength on a given trial.
- λ = Total associative strength supported by the outcome.
- ΣV = The expected outcome given all cues present.
- α = Attention to cues (salience).
Key point: Learning happens only when there is a prediction error.

Beesley and Le Pelley (2011) used eye-tracking in a learning task.
Participants viewed stimuli (chemicals) and outcomes (symptoms in Mr. X) on a screen.
The study tracked whether participants looked at the word 'Addexium' (the CS).