Transcript LTJan15
PSY402 Theories of Learning Wednesday January 15, 2003 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. 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) 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. 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 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 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. 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. 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. 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. 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. 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. 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. 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. 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.