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)