Classical Condititoning (CC) Chapter 4 continues & a little from Chapter 5 1 overshadowing, blocking, and latent inhibition. Conditioning occurs to specific stimuli only, despite close pairing of other stimuli with the US. 2 Overshadowing 3 Overshadowing 4 Suppose that you were stung by a wasp during a walk. Do you develop a conditioned fear response to every stimulus associated with that event (e.g., the trees surrounding you, the butterfly fluttering by, and the cloud formation in the sky)? No! Rather, it s more likely to develop a fear response to stimulus which was most salient at the time of being stung, such as the sight of the wasp or the buzzing sound it makes. The positive feelings generated by the music of a rock band will be most strongly associated with the most salient member of that band (e.g., the lead singer) 1
A compound stimulus consists of the simultaneous presentation of two or more stimuli (e.g., the sound of a metronome is presented at the same time as a light). 5 the presence of an established CS interferes with conditioning of a new CS. 6 Suppose that a light is first conditioned as a CS for salivation. If the light is then combined with a CS metronome to form a compound, and this compound is then paired with food, little or no conditioning occurs to the metronome. 7 8 Imagine that you have to make an unpopular announcement to your employees. Based on blocking, you would do well to make it a joint announcement with another manager who is already disliked by the employees (one who is already an aversive CS). The employees might then attribute most or all of the bad news to the unpopular manager, and you will be left relatively unscathed. 2
9 10 Taste aversion. Response is nausea Based on Taste aversion. Shrimp à Nausea aversive stimulus response Shrimp + Vegetables : Nausea aversive+ neutral Shrimp à Nausea Vegetables à No nausea Latent Inhibition A familiar stimulus is more difficult to condition as a CS than is an unfamiliar (novel) stimulus. So, it means that an unfamiliar stimulus is more readily conditioned than a familiar stimulus. 11 Latent Inhibition 12 If a rabbit in a grassy field is attacked by a coyote and then escapes, it will be much more adaptive for the rabbit to associate the attack with the novel scent of the coyote than with the familiar scent of grass. A conditioned fear response to that scent will help the rabbit avoid such attacks in the future. A conditioned fear response to grass, however, will be completely maladaptive because the rabbit is surrounded by grass day in and day out and often feeds on it. 3
Questions: Answer: Overshadowing. Q: In, the presence of an established CS interferes with conditioning of another stimulus. A: blocking 13 14 Q: Because Jez has a history of getting into trouble, he often catches most of the blame when something goes wrong, even when others are also responsible for what happened. This is most similar to the phenomenon of. A: blocking Q: In, a familiar stimulus is more difficult to condition as a CS than is an unfamiliar stimulus. A: latent inhibition The Rescorla-Wagner theory proposes that a given UCS can support only so much conditioning, and this amount of conditioning must be distributed among the various CSs available. Stronger USs support more conditioning than do weaker USs. 15 If the tone is a bit more salient than the light, then when tested separately, the tone elicits 6 drops of saliva while the light elicits 4. 16 If the tone was even more salient than the light, then overshadowing might occur. V is the number of drops of saliva the tone elicits. 4
According to the Rescorla-Wagner theory, the amount of conditioning that occurs is limited and must be distributed among the various CSs available. 17 Let s take a blocking procedure. One stimulus is first conditioned to its maximum associative value. 18 According to the Rescorla-Wagner theory, overshadowing occurs because the more salient CS picks up (most/little) of the associative value available in that setting. the tone has already acquired that much value. The light can therefore acquire no associative value because all of the associative value has already been assigned to the tone. When the two stimuli are later tested for conditioning, the following occurs: According to the Rescorla-Wagner theory, blocking occurs because the (CS/NS) in the compound has already picked up all of the available associative value. 19 Suppose we condition a tone to its maximum associative value, as follows: Tone (V = 0): Food (Max = 10 ) Salivation Tone (V = 10) Salivation 20 and then do the same for the light: Light (V = 0): Food (Max = 10 ) Salivation Light (V = 10) Salivation 5
According to the Rescorla-Wagner theory, after several pairings of the compound stimulus with food, the total associative value of the compound stimulus will be reduced to 10: [Tone + Light] (V = 10) Salivation When each member in the compound is tested separately, its value also will have decreased: Tone (V = 5) Salivation Light (V = 5) Salivation 21 Suppose a tone and a light are each conditioned with food to a maximum associative value of 8 units. If the tone and light are combined into a compound stimulus for further conditioning trials, the associative value of each stimulus must necessarily (decrease/increase). This is known as the o effect. 22 This is so called overexpectation effect! A compound stimulus consists of a buzzer and a light flash, each of which has 0 units of associative value. This compound stimulus is then repeatedly paired with a sweet drink that can support a maximum associative value of 15 units. Following these pairings, the buzzer has acquired 14 units of associative value. This means that the light flash has at most acquired units of associative value, which is a demonstration of. 1; overshadowing 1; blocking 15; simple conditioning 23 14; the overexpectation effect 6