Operant conditioning

Operant conditioning

In classical conditioning, the presence of one stimulus(e.g. meat powder) is conditional on the presence of another stimulus (e.g., a bell)

What else can an animal learn, besides the relationshipof two stimuli?

It is also possible for the animal to generate a responseand for that response to have consequences:

Operant conditioning

Act cute, you get pet

Poop on the rug, you get scolded

Note that the thing to be learned is not a UR. Animal emits a response (pooping,

acting cute), and it is rewarded or punished.

Edward Thorndike

Thorndike’s Law of Effect

“If a response in the presence of a stimulus is followed by a satisfying event, the association between the

stimulus and the response is strengthened. If the response is

followed by an annoying event, the association is weakened.”

Today we’ll cover:

• Basics of operant conditioning

• What makes operant conditioningeffective.

• The problem of definition in o.c. (not just that “animals seekrewards”).

Thorndike’s method was limited because each trial took so long.

A stripped-down environment

Free operant curve, from a cumulative recorder

Steep slope=many responsesShallow slope=few responses

What would the curve look like if 20 bar presses food?

To really teach the animal you would shape it’s behavior. . .

Fixed ratioConsistent ratio of number of responses & number of reinforcers

Example: factoryPiece work

Steady response Easy to extinguish

Variable ratioSet ratio of number of responses & number of reinforcers, but can vary locally

Example: slot machine

Rapid responseHard to extinguish

Fixed interval

First response after a specific amount oftime since the last reinforcement

Example: studying for exams

Little response untiljust before reinforcement:then rapid responseFairly easy to extinguish

Variable intervalFirst response after a some amount of time since the last reinforcement: amount of time can vary, locally

Example: checking email

Steady responseHard to extinguish

Contingencies don’t just add good stuff. . .

Positive Reinforcement

Negative Reinforcement

PunishmentAdd to environment

Negative Punishment(Extinction)

Take away from

environment

Increase probability of behavior

Decrease probability of behavior

Result

Action

e.g., food

e.g., escape

e.g., spanking

e.g., being grounded

Complex contingencies: Would this work?

Bar press reinforced, but ONLY when red light is on.

YES! This is called differential reinforcement

How does differential reinforcement apply here?

Reinforcer = food.Response = hoveringDifferential signal = looking up.

What’s happening, and what should the birds do?

What’s happening= differential sign has changedWhat should the birds do = stop responding

Moments later, birds are leaving

Operant conditioning--what makes it effective?

• Schedule of reinforcement

• Temporal contingency

• Belongingness

• Quality, quantity of reinforcer

• What else the animal might do

T-maze: temporal contingency

Condition 1: immediate reward (.5 sec)

!

Condition 2: delayed reward (5 sec)

!

Effectiveness--temporal contingencyThe delay between the animal’s act that you

are reinforcing, and the reinforcer.

0

5

10

15

20

25

30

35

0 5 10 15 30 60 150

Delay (seconds)

Lea

rnin

g st

reng

th (

arbi

trar

y un

its) Grice (1948)

Wolfe (1934)

WHY does learning drop off with delay??

Condition 2: delayed reward (5 sec)

!

Operant conditioning--what makes it effective?

• Schedule of reinforcement

• Temporal contingency

• Belongingness

• Quality, quantity of reinforcer

• What else the animal might do

Belongingness

• Thorndike tried to condition his cat to yawn or scratch to escape box--he proposed belongingness

Instinctive drift

• A concept related to belongingness: instinctive drift (Breland & Breland.)

•Motivational state can also influence; a hungry animal does more food-seeking behaviors. . .

Digging Digging, scratching, rearing

Quality/quantity of reinforcerWorks as you would expect.

What else might the animal do?

It’s not as simple as “the animal Maximizes good things, minimizes”bad things.

Even humans don’t do this, if the situation getsmoderately complex.

Example

Variable ratio Variable interval

What’s the optimal strategy?

Variable ratio Variable interval

Optimal is to hit VR almost exclusivelyand occasionally hit the VI. Instead, they respond to equalize ratios of work/reward

The problem of definition

What is a reinforcer?

The problem of definition

Thorndike called a reinforcer something “thatbrings about a satisfying state of affairs.”

How do we know when animal is satisfied?Presumably, when the animal will work toachieve this state of satisfaction.

But that’s circular

What will the animal work for (e.g., peck)?

What’s a reinforcer?

Something pleasurable.

What’s pleasurable?

Something that increases behavior, that animal will work to get

Another definition: physiological homeostasis

Animal seeks to lessen thirst, hunger, etc.Definition of reinforcement is based on biological drives.

Learning = a “stamping in” of the work that needs to be done to reduce hunger.E.g, “I must not only consume and chew to get nourishment. I also must press the bar, then consume, then chew.

Problems

Too many drives were proposed.

Animals (and people) do things that seem more likely to raise drives, not lower them

Reinforcement as behavioral regulation

Premack principle: Given two responses arranged in an operant conditioning procedure, the more

probable response will reinforce the less likely behavior.

Which do you want to do: play pinball or eat candy?

Must eat candy to play pinball

Must eat candy to play pinball

These kids treat candy eating as work: do it to get to play pinball.

These kids eat candy but don’t care that they have earned pinball time.

Behavioral homeostasis & bliss point—a clever, not-quite-right idea

0

5

10

15

20

25

30

35

0 15 30 45 60

Minutes running

Min

utes

dri

nkin

g

Restricteddrinking

Normally, animal likes to be at gray spot (15 minutes ofeach--now it can’t be at gray spot. What will it do?

0

5

10

15

20

25

30

35

0 15 30 45 60

Minutes running

Min

utes

dri

nkin

g

Restricteddrinking

IN THEORY you should be able to predict what animal willdo--it will select spot on blue line that is as close as possible to it’s “bliss point”. IN REALITY this predictionsometimes works, sometimes doesn’t.

Reinforcement--final word

In the end, we still don’t have a good definition of the concept. Premack

Principle is as close as we get. Nevertheless, the concept of reinforcement seems useful.

Applications

• Animal training

• Biofeedback

• Education

• Token Economies

BiofeedbackOperant conditioning of the autonomic

nervous system.

For years, not explored because no one thought it could possibly work.

Apply operant conditioning principles to education

1. Make sure student doesn’t make mistakes; guidebehavior.2. Review frequently.

Little enthusiasm. Teachers didn’t like itfor their own reasons. Students were bored.

Token economies

Used in some mental health institutions, and some classrooms.

Mrs. Ahlersmeyer’s 3rd grade class, Lafayette Elementary, Lafayette, IN

• Students earn a “salary” (marbles).• Outstanding work or behavior earns bonuses. • Students allowed 5 sick days per quarter, after

that, they are docked pay.• Students charged rent for their use of desk, and for

any school property lost or damaged.• Students docked pay for inappropriate behavior.

Use is controversial because it seems “dehumanizing” (mental patients) or

because it seems that you’re “paying” students for behavior that

they should want to do.

Applications

• Animal training

• Biofeedback

• Education

• Token Economies