PSY402 Theories of Learning

1. PSY402Theories of Learning Wednesday January 15, 2003

2. Examples of Conditioning • Popcorn at the movies. • Fear of flying -- stronger with more turbulence (a stronger UCS). • An antelope shying away from low tree branches. • Nausea at the smell of alcohol after a hangover.

3. Conditioning Situations • Sign-tracking (autoshaping) – animals must recognize signs of food (UCS) and respond (UCR). • Pigeons pecking at key. • UCR, not an operant response, because behavior is specific to the stimulus. • Eyeblink conditioning • UCR is rapid, CR is slow. • Many trials are needed (100 pairings)

4. Fear Conditioning • Avoidance is not a good measure of fear. • Suppression of an operant behavior occurs with a feared stimulus. • First – an operant behavior is learned. • Second – a CS is paired with an aversive UCS. • Third – the CS is presented in the operant chamber.

5. Suppression Ratio During CS SuppressionRatio = During CS + Without CS • The amount of time during and without the CS is equal. • The more fear, the lower the suppression ratio. • Ratios typically fall between 0 and .5

6. Flavor Aversion Learning • Garcia – rats will not drink water with saccharin if they get ill after drinking. • Significant avoidance occurs after just one trial. • Human food aversions are related to illness (89%). • Even if illness occurs hours later it is linked to the previous meal. • Not cognitive – know food not to blame

7. Conditioning Paradigms • Delayed conditioning – the CS onset precedes the UCS onset. • Trace conditioning – the CS starts and ends before the UCS onset. • Simultaneous conditioning – the CS and UCS occur together. • Backward conditioning – the UCS starts and ends before the CS onset.

8. Temporal Conditioning • No CS is presented. • The UCS occurs at regular intervals. • A CR eventually occurs just before the UCS. • Mechanism: a biological state typically provides the CS. • Waking up just before the alarm goes off.

9. Importance of Timing • A cue (CS) needs to be a good predictor of the UCS. • Optimal inter-stimulus-interval (ISI) varies with the kind of response. • The latency to respond is different for different reflexes (saliva, heart rate) • Too long or too short intervals result in weaker conditioning. • Intermediate CS’s form a bridge.

10. Importance of CS Strength • CS intensity affects CR strength only when the CS intensity varies. • If the CS strength is always the same, then the CS strength doesn’t affect the size of the CR. • Both dogs must bite in order for their size to matter. • In order for CS intensity to matter, it must signal something.

11. Importance of UCS Strength • Strength of the CR increases with strength of the UCS. • The more intense the air puff, the stronger the eyeblink CR.

12. Salience of the CS • Salience refers to how noticeable a stimulus is – how likely an organism is to notice it in the environment. • Preparedness (evolutionary predisposition) makes some CS more salient than others. • The more salient the CS, the stronger the CR and faster learning.

13. Predictiveness of the CS • Predictiveness refers to how reliably the CS is associated with the UCS. • When two or more CS’s are present, only the most reliable elicits a CR. • When the CS occurs with the UCS more often than the UCS occurs alone, conditioning occurs. • A CS alone weakens conditioning.

14. Blocking • Presence of a previously conditioned CS (existing predictive cue) prevents conditioning of a new CS. • Parent threats – presence of fear of the parent prevents acquisition of fear to another stimulus.

15. Implications for Parenting • Threats (CS) should reliably be accompanied by punishment (UCS) or they will be ignored. • Timing of threat (CS) and punishment (UCS) should be close together – not wait until Dad gets home. • Fear of parents (CER) may block conditioning of any other CS.