Principles of BehaviorSixth Edition

Richard W. MalottWestern Michigan University

Power Point by Nikki Hoffmeister

Chapter 17

Ratio Schedules

What is a Schedule of Reinforcement?

Schedule of Reinforcement:• The way reinforcement occurs • because of the number of responses, • time between responses, • and stimulus conditions.

What is Continuous Reinforcement?

Continuous Reinforcement (CRF):

• A reinforcer follows each response.

Intermittent Reinforcement:

• Reinforcement occurs, but not after each response.

When should you use CRF?

• Continuous reinforcement is usually best for shaping or maintaining difficult behavior.– Shaping vocal responses

What is a Fixed-Ratio Schedule?

Fixed-Ratio (FR) Schedule of Reinforcement:

• A reinforcer follows

• a fixed number of responses.

What kind of responding does a fixed-ratio schedule produce?

Fixed-Ratio Responding:

• After a response is reinforced,

• no responding occurs for a period of time,

• then responding occurs at a high, steady rate

• until the next reinforcer is delivered.

Non-Cumulative Graph

Non-Cumulative Graph

• The horizontal line (x-axis) indicates the passage of time

• Each vertical line indicates a response

• At the end of each ratio of 8 responses a reinforcer is delivered (indicated by star)

• After each star, the line is flat, indicating no response occurs for a while– Post-reinforcement pause

Post-Reinforcement Pause

• Characteristic of fixed-ratio-maintained behavior

• The length of the pause is proportional to the size of the ratio

High Ratios

• If you wish to establish a high ratio requirement,

• you need to do so gradually,

• raising the ratio from 2 to 4 to 6 responses and up.

• Otherwise the response may extinguish.

What is the general rule for establishing intermittently

reinforced behavior?• First, use continuous reinforcement

• and gradually increase the intermittency of reinforcement

• as responding stabilizes at a high rate.

The Cumulative Graph

Cumulative Graph

• Behavior analysts often use this type of graph when studying schedules of reinforcement.

• The vertical axis (ordinate) is labeled cumulative frequency of responses as opposed to a non-cumulative graph in which the ordinate is labeled responses.

• The post-reinforcement pause is where the slope of the line is zero.

What is a Variable Ratio Schedule?

Variable-Ratio (VR) Schedule of Reinforcement:

• A reinforcer follows

• after a variable number of responses.

What type of responding does a VR schedule produce?

Variable-Ratio Responding:

• Variable-ratio schedules produce

• a high rate of responding,

• with almost no post-reinforcement pausing.

VR Schedules

• VR 50– This means that a reinforcer is delivered after

an average of 50 responses– An FR 50 means the reinforcer is delivered

after exactly 50 responses

• Intermittent Reinforcement:– Generic term that includes both fixed and

variable ratio schedules

Reinforcer vs. Reinforcement

• What is a specific pellet of food for a deprived rat?– A reinforcer– Reinforcement

• The immediate delivery of a pellet contingent on a deprived rat’s lever press with a resulting increased rate of pressing?– Reinforcer– Reinforcement

Reinforcer vs. Reinforcement

• What is a quarter for a deprived professor?– Reinforcer– Reinforcement

• What is the immediate delivery of a quarter, contingent on a deprived prof’s pleading for a raise, with a resulting increased rate of pleading?– Reinforcer– Reinforcement

Ratio Schedules in Everyday Life

• Are slot machines in casinos examples of everyday VR schedules?

• No; there are 5 reasons why

4 Reasons Why Slot Machines are Not VR Schedules

1. It’s loaded with learned reinforcers in addition to the silver dollars

• Like those fruits that appear in the window, one after the other

• You get 2 cherries in a row…a big reinforcer

4 Reasons Why Slot Machines are Not VR Schedules

2. The variable amount of the reinforcer you get at the end of the so-called VR

• Sometimes you get only one silver dollar• Sometimes it’s 10, 18, so on• None of that’s like the ratios the behavior

analysts study in the Skinner box

4 Reasons Why Slot Machines are Not VR Schedules

3. The size of the ratio is much smaller than is typical in the Skinner box of the professional research lab

• Like a VR 100• In a casino, people would not play if

machines had ratios of 100

4 Reasons Why Slot Machines are Not VR Schedules

4. The emotional reaction is itself reinforcing

• Near misses are reinforcing

Intermediate Enrichment

• Free-operant procedures– Most Skinner-box research involves free-

operant responding– The animal is free to respond at various

frequencies (1 lever press per minute to 100 lever presses per minute)

– There is no S∆ after each response, so there is no inter-trial interval between each response and the next SD

Discrete-Trial Procedure

• There is an SD,

• a single response,

• and an outcome,

• followed by an S∆ (intertrial interval);

• then the next trial starts.

In the Classroom:Discrete-Trial Procedure

SD: Sue says, “Jimmy point to the horse.”

Response: Jimmy points to the horse.

Outcome: Sue says, “Good boy, Jimmy.” (a learned reinforcer for Jimmy)

S∆ (Inter-trial Interval): Sue says nothing

In the Classroom:Free-Operant Procedure

SD: Sue and Jimmy at the snack table.

Response 1: Jimmy says, “Juice please.”

Outcome: Sue gives him a sip of juice.

Response 2: Jimmy says, “Juice, please.”

Outcome: Again, Sue gives him a sip of juice.

S∆: Sue and Jimmy leave the snack table.

Discrete Trial vs. Free Operant

Discrete Trial Free Operant

Is there an SD and an S∆?

Yes Sometimes

Is there an inter-trial interval?

Yes Usually not

The measure is…

Latency or accuracy

Rate

Advanced Enrichment

• Hybrid Discrete-Trial/Free-Operant Procedure– Each free-operant response, itself, consists of

a discrete trial.

Example

• Sue and Jimmy are in the structured-play area

Response 1: Jimmy picks up a piece of the puzzle and puts it in the puzzle form

Response 2: Jimmy picks up a 2nd piece and puts it in the puzzle form

Response 3: Jimmy picks up a 3rd, final piece, and puts it in the form

Outcome: Jimmy has completed the puzzle and sees a picture of Barney. Sue says, “Good job.”

Why Hybrid?

• This is an example of a discrete trial, because each piece Jimmy puts in the puzzle is an SD for the next response.

• It is also an example of free operant because Jimmy is free to place each puzzle piece as fast as he “wants,” and…

• A measure of his behavior would be a rate measure (e.g., 8 pieces per minute).

On DickMalott.com

• Chapter 17 Advanced Enrichment Section– In Search of the Everyday Variable Ratio

Join us for Chapter 18:Interval Schedules