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Psychology 2250. Last Class Characteristics of Habituation and Sensitization -time course -stimulus-specificity -effects of strong extraneous stimuli (dishabituation) Habituation and Sensitization in Aplysia Opponent Process Theory Pavlovian Conditioning Excitatory Conditioning. - PowerPoint PPT Presentation
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Psychology 2250
Last ClassCharacteristics of Habituation and Sensitization
-time course-stimulus-specificity-effects of strong extraneous stimuli (dishabituation)
Habituation and Sensitization in Aplysia
Opponent Process Theory
Pavlovian ConditioningExcitatory Conditioning
• Fear Conditioning
• Eyeblink conditioning
• Sign Tracking (Autoshaping)
• Taste Aversion Learning
Some Examples of Excitatory Classical Conditioning
Fear Conditioning
Little Albert
With rats, the aversive stimulus (US) is typically a brief shock delivered to the feet through a metal grid floor
The CS may be a light or tone
Tone Shock
The CR in this case is typically freezing
Fear Conditioning
Although the typical response of rats is to become motionless, we don’t always measure freezing directly.
We often measure conditioned fear by observing how the CS disrupts the animal’s ongoing behavior
A popular technique is the Conditioned Emotional Response (CER) procedure
Also called Conditioned Suppression
Conditioned Emotional Response (CER)
First train rats to barpress for food until they reach stable baseline of responding
Then give Pavlovian pairings of T shock
The shock will normally stop the rats from making the BP response
After a few T shock pairings, look at suppression of BP when the T comes on.
Our measure of conditioning to the T is a suppression ratio
suppression ratio = B/A+B;
A = # BP before tone comes on (pre-CS)B = # BP during tone A+B = total BP
If Tone is 5 sec, then measure BP for 5 sec before tone comes on and for 5 sec while the tone is presented.
For ex., B/A+B = 20/20+20 = 20/40 = 0.5
suppression ratio = 0.5 (indicates no conditioning)
Rat is equally likely to make response in the presence or absence of the CS.
If the T CS is not effective, then the rat will make as many barpresses during the tone as during the pre-CS interval before the tone comes on.
If the CS is effective, the suppression ratio will be closer to 0.
For ex., B/A+B = 10/ 30+10 = 10/40 = .25(i.e., 10 responses during the T, but 30 pre-CS responses)
A value closer to 0 means more suppression (i.e., better/stronger CS)
Eyeblink ConditioningThe procedure for classical conditioning of the eye-blink response.
Sign Tracking or Autoshaping
Much of the work on autoshaping has been done using pigeons as subjects
Keylight food
Keylight = light comes on behind a translucent diskcalled a key
After a few pairings of this keylight with food, the pigeons peck at the diskFood is given whether the pigeons peck at the key or not
Sign Tracking or Autoshaping
Taste-Aversion Learning
Subjects consume a novel-flavored food or drink.
Then subjects are given a treatment (e.g., drug, radiation, motion) which makes them sick.
Then when the flavor is presented again, animals don’t consume as much as on the original trial
We can’t measure sickness directly (as with salivation) but we infer the association has taken place when the animal stops drinking.
Taste-Aversion Learning
CS = tasteUS = drug, radiation
Saccharin LiCl
Special features of conditioned taste aversions (CTA)-one trial learning-long-delay learning
Excitatory Pavlovian Conditioning Procedures
The course of classical conditioning is determined by the timing of the CS and the US
Each presentation of the CS and US represents a singleConditioning trial
The time from the end of one conditioning trial to the startof the next trial is called the intertrial interval or ITI
The time from the start of the CS to the start of the US is the interstimulus interval or ISI or CS-US interval
ISI < ITI
Excitatory Pavlovian Conditioning Procedures
Time
Traceconditioning
CS
US
On Off
Short-delayedconditioning
CS
US
Long-delayedconditioning
CS
US
Backwardconditioning
CS
US
Simultaneousconditioning
CS
US
CS-US Interval
Effects of the CS-US intervalon the strength of the CR
Measuring Conditioned Responses
To compare the effectiveness of different conditioning procedures, we use a test trial – present the CS without the US
Behavior during the CS can be quantified in several ways:magnitudeprobabilitylatency
Control Procedures
To determine whether changes in behavior are due to Conditioning procedures, must have a comparison group (Control Group)
Pseudoconditioning – increased responding not due to a CS-US association (i.e., presentations of the US alone)
Random Control procedure – present CS and US at random during the experiment
Explicitly unpaired control – CS and US are presented far apart to prevent their association
AcquisitionThe time during which the subject acquires the association,as evidenced by the development of the CR
i.e., autoshaping in pigeons— see increase in # pecks at the
keylight)
ExtinctionOccurs when a CS is given without a US. The CR strength declines during extinction trials. (covered in Ch. 9)
Basic Stages in a Conditioning Experiment
Phases of classical conditioning: Classical conditioning proceeds through several phases, depending on the time of presentation of the two stimuli. If the conditioned stimulus regularly precedes the unconditioned stimulus, acquisition occurs. If the conditioned stimulus is presented by itself, extinction occurs. A pause after extinction yields a brief spontaneous recovery.
Extinction does not abolish the CS-US association
Spontaneous recovery Give a rest period after the extinction phase and the CR will recover
A likely explanation is renewed attentionacquisition— increases attention to the CSextinction— decreases attention to the CSS.R. — renewed attention to the CS
DisinhibitionIf you present a novel stimulus along with the CS during extinction, see recovery of the CR.
For ex., pair L shock in rats, see freezing in anticipation of shock. Freezing decreases during extinction (animals start to move around again).
Present T with the L during extinction and the freezing reappears.
Similar to dishabituation
CR renewalIf extinction occurs in a different environment than acquisition, putting the animal back in the original environment evokes the CR again.
For ex., Room A: T food pairings (acquisition— dog salivates to T)
Room B: T no food (extinction— dog stops salivating to T)
Put dog back in Room A againDog will now salivate to T again.
.These 4 procedures show that extinction does not abolish the CS-US association
The CR is merely inhibited
ReinstatementExposure to the US alone can reinstate conditioned responding
T shock pairings; see CR to TGive T alone; CR decreasesGive shock alone Present T and see CR
Inhibitory Pavlovian Conditioning
Stimuli can become conditioned to signal the absence of a US in addition to signaling the presence of a US— such learning is called Inhibitory Conditioning
CS+ = excitatory CS = CS USCS- = inhibitory CS = CS no US
Conditioned inhibition teaches an animal to inhibit, or hold back, a CR.
An important prerequisite for conditioning a stimulus to signal the absence of some US is that the US be periodically presented in that context or situation
For ex., put rat in a boxT - (i.e., no US)
This means nothing to the ratBut if the rat is normally given food in that box, then T could become a conditioned inhibitor.
Inhibitory Conditioning only occurs if there is an excitatory context
For the absence of a US to be a significant event,the US must periodically occur in this situation
Procedures for Inhibitory Conditioning
Conditional (standard)
CS+ (CS US)CS+/CS- (CS/CS no US)
— the CS- gradually becomes a signal for the absence of the US — only get the US when the CS+ occurs. When the CS+ occurs in combination with the CS-, no US is given
What is the excitatory context in this example?
Explicitly unpaired/Negative contingencyExplicit CS+ training is not necessary for inhibitory conditioning
Negative CS-US contingency (correlation)p(US/CS-) < p(US/no CS)
If a US is presented in the experimental chamber but it is not signaled by explicit cues (i.e., no CS+), get some conditioning to the experimental chamber cues
Box; normally get food UST- ; T becomes a CIp(food/T)< p(food/no T)