PSY 402Theories of Learning

Chapter 3 – Nuts and Bolts of Conditioning

(Mechanisms of Classical Conditioning)

Classical vs. Instrumental The modern view is that these two types of learning

involve similar learning processes, but differ in the following ways.

1. In Classical conditioning, two stimuli are associated with each other but in Instrumental conditioning, a stimulus and a response are associated.

2. In Classical conditioning, the response is a reflex or involuntary action but in Instrumental conditioning, the response is a voluntary, freely emitted behavior.

Pavlov’s Conditioned Reflex Conditioning -- a stimulus that initially

produces no response can acquire the ability to produce one.

Learning occurs through pairing in time and place of one stimulus with another stimulus that produces an involuntary response.

Political Classical Conditioning

Terminology of Conditioning Unconditioned stimulus (US or UCS)

Elicits a reflexive response without learning. Unconditioned response (UR or UCR)

The response that occurs with a US, typically a reflex, emotion or drug state

Involuntary and automatic.

More Terminology Neutral stimulus

A stimulus not capable of producing an unconditioned response (before learning).

Conditioned stimulus (CS) A previously neutral stimulus that has acquired

the ability to evoke a response. Conditioned response (CR)

The learned response, often similar to the UCR, an involuntary reflex, emotion or drug state.

Prior to conditioning

Neutral stimulus(tone)

(Orientation to soundbut no response)

UCS(food powder in mouth)

UCR(salivation)

During ConditioningNeutral stimulus

CS (tone)

UCS(food powder)

+CR

(salivation)

After conditioningCS

(tone)CR

(salivation)

Conditioning Processes Stimulus generalization – stimuli like the CS

become able to evoke the conditioned response.

Extinction – if the UCS and CS are not paired, the CS loses its ability to produce a conditioned response.

Spontaneous recovery – an extinguished CS briefly returns but quickly goes away again.

What is Learned? Pavlov believed the association was between

the two stimuli (tone and meat powder), not between the tone and salivation.

Stimulus substitution

Either is possible

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)

3.7 Autoshaping in pigeons (Part 1)

3.7 Results of autoshaping tests in pigeons (Part 2)

3.5 Design of eyeblink conditioning experiment in rabbits (Part 1)

3.5 Results of eyeblink conditioning experiment in rabbits (Part 2)

Conditioned Emotional Responses Fear is an anticipatory pain response based on

past experience. Fear is conditioned (becomes a CR) whenever

a CS is associated with an aversive (painful or undesirable) event.

Fear motivates two responses: Escape (when pain is present) Avoidance (when pain is imminent)

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 and the effect on operant responding is measured.

3.6 Conditioned suppression in rats (Part 1)

Suppression Ratio

During CSSuppression Ratio = 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 This will be on the midterm

3.6 Conditioned suppression in rats (Part 2)

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 – you can know the food is not to

blame and still feel an aversion to it.

Acquired Changes in Response Habituation – response to a repeated stimulus

decreases with non-threat experience. Sensitization – response to a variety of stimuli

increases with a single threat experience. Examples:

Ingestional neophobia, fear of new food Rats orient less toward light, startle decreases Chicks are less frightened by shadows flying

overhead with repeated exposure.

Factors Affecting Conditioning Timing – how closely in time are the CS and

UCS, and which occurs first. Novelty of the CS and UCS. Intensity (strength) of the CS and UCS. Consistency of the pairing between the CS

and UCS. If one or the other appears alone then

conditioning is weakened.

Stimulus Presentation 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. These paradigms will be on the midterm

3.8 Different ways to present CS and US in time

This works best

This doesn’t work at all

This isn’t as good as delayed

The longer the gap (trace interval) the worse this works

Massed vs Spaced Trials Better learning occurs when trials are spaced

out over time (spaced), rather than bunched together (massed).

Memory consolidation or rehearsal may be needed between trials.

The ratio between the exposure to the CS and the time in-between is the important factor. If both are the same duration, learning is weaker.

3.9 Trial spacing in Pavlovian conditioning

This doesn’t work as well

This works best

Importance of Novelty Preexposure to the CS (before it is paired with

the UCS) reduces learning. Called latent inhibition because it inhibits

learning of the CS-UCS association. The same thing happens with preexposure to

the US (before it is paired with the CS). Called the US preexposure effect

Other, more novel stimuli are more likely to become associated with the UCS.

Stimulus Intensity (Strength) The stronger the US (UCS), the faster the

learning and the stronger the association. The stronger the CS, the better the learning.

Salience – how attention-getting the stimulus is in relation to other stimuli in the environment.

The most salient CS becomes associated with the UCS.

An overpowering CS may elicit a response of its own, preventing learning.

Pseudo-conditioning Responses to the CS may occur due to the

strength of the UCS, not learning. Once air has been puffed at the eye, blinking may

occur in response to any stimulus that comes next, without any learning.

Sensitization resulting from an intense UCS may cause the response to a CS to be increased, even when there is not greater learning.

A control group lets you tell the difference.

3.10 Bernstein’s experiment on taste aversion learning

Classical Conditioning Adaptation Organisms learn to recognize and respond

selectively to the signals that are important in their environment.

Cues associated with food evoke digestion: salivation, gastric juices, insulin secretion. Taste aversion learning – illness makes us avoid

foods that were eaten just prior to feeling sick. Food preferences are associated with nutrients.

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.

Territoriality Environmental cues can become associated

with sexual rival males in gourami fish. Pairing the light with the rival signaled the other

fish to prepare so it was able to be more aggressive.

Presenting the light without pairing it with the rival had no effect.

Courtship behavior can also be conditioned, leading to more successful nestbuilding, etc.

Fear Conditioning Freezing is a universal response to threat.

Animals that freeze are less likely to be attacked. Fear is an anticipatory pain response.

It occurs in response to stimuli that have been aversive in the past and motivates escape or avoidance behaviors.

Fear also releases endorphins in rats who are confronted by the smell or sight of a cat.

Conditioning and Addictions Drugs can be associated with environmental

cues present when the drugs are taken. Instead of the drug response being

conditioned, an opposite adaptive response is conditioned that lessens the drug’s effect. This is called drug tolerance.

Taking a drug under novel circumstances can produce a drug overdose because the compensatory effect is not present (no cues).

Sign Tracking (Auto-Shaping) Sign tracking occurs when a stimulus (cue) in

the environment is associated with reward or punishment. The sign stimulus motivates approach or

avoidance behavior because of what it signals. Negative sign tracking occurs when a sign

motivates withdrawal instead of approach. Some signs signal safety because they mean a

bad thing is less likely to occur.

Extinction Associations are learned when they enhance

survival, but conditioning decreases when the expected consequence no longer occurs.

Extinction occurs with both instrumental and classical conditioning. Spontaneous recovery occurs after extinction has

been learned, but a break in exposure to the stimulus occurs.

After spontaneous recovery, extinction returns.

Timing of Stimuli The strength of both instrumental and

classical conditioning depends on the timing of events.

Reward or punishment must immediately follow the emitted response in order to strongly affect behavior.

Two stimuli must occur close together in time in order for them to be associated with each other.

Size of the Stimuli The strength of both instrumental and

classical conditioning also depends on the size of the stimuli.

Larger rewards produce a stronger response than smaller ones.

More intense stimuli are better signals and evoke greater conditioned responses. More fear, more saliva.

Preparedness Affects Learning Both instrumental and classical conditioning

are affected by preparedness (the innate nature of the organism).

Flavor aversion learning is easier with taste cues than with visual cues, but not shock.

Rooting behaviors interfere with learning for pigs trained to put a wooden coin in a “bank”.

Some hamster behaviors are easier to learn.

Humans Show Preparedness Humans show preparedness too, appropriate

to our species. Nausea can be associated with tequila but not

with friends or a shot glass. Snake and spider phobias may be especially

prevalent due to preparedness. People associate shock with spiders or snakes

more readily than with flowers or mushrooms.