PSY402 Theories of Learning Friday January 17, 2003
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. A UCS alone weakens conditioning.
Blocking In order to become a CS, a stimulus must provide information not already signaled by other cues. Surprise is important to conditioning. Presence of a previously conditioned CS (existing predictive cue) prevents conditioning of a new CS. Parent threats –fear of the parent prevents learning to fear another cue.
Other 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.
Extinction Extinction – a method for eliminating a conditioned response. Extinction paradigm: Present the CS alone (without the UCS). With repeated exposure to the CS, it stops being a predictor of the UCS and the CR decreases and eventually stops.
What Influences Extinction? The total duration of exposure to the CS alone, not the number of trials, determines how fast the CR is extinguished. Shipley measured effects of tone- shock pairing on water licking. Suppression ratio for licking behavior 100 sec or 25 sec exposures to CS alone.
Spontaneous Recovery Pavlov – extinction is caused by inhibition of the CR. Spontaneous recovery occurs when inhibition is temporarily removed. Continued experience of the CS without the UCS results in long- term suppression of the CR.
Conditioned Inhibition CS+ the original CS CS-a new CS similar to CS+ Presentation of CS- without the UCS inhibits the CR. The idea is that CS- becomes associated with the absence of the UCS – it becomes an “all clear” cue. CS+ is associated with presence of the UCS.
Other Kinds of Inhibition External inhibition – presence of a novel cue during conditioning inhibits the CR. Latent inhibition (learned irrelevance) – not really inhibition. Preexposure to the CS (without the UCS) inhibits later conditioning (+ or -) Inhibition of Delay – the CR is withheld until an appropriate time.
Disinhibition Disinhibition – removal of inhibition. The CR increases in strength. Presentation of a novel stimulus during extinction interrupts it. Example: Kimmel – disinhibition of inhibition of delay occurred with a novel stimulus. CR with withheld 4.0 secs but 2.3 secs with a novel stimulus