Chapter 10: Developing Behavioural Persistence with Schedules of Reinforcement

Intermittent Reinforcement

• schedule of reinforcement in which not every response produces reinforcement

• every response = continuous

• no response = extinction

• continuous reinforcement is used when a new behaviour is being acquired

  • intermittent is used to maintain a behaviour

Advantages of Intermittent Reinforcement

• reinforcer is effective longer due to slower satiation, particularly with consumable

• behaviour is more resistant to extinction

• individuals word more consistently

• behaviour will more readily be transferred to control by reinforcers in the natural environment

Free Operant

• response is free to occur at any time and repeatedly in the presence of a particular stimulus

• dependent measure: rate of responding

Discrete Trial

• response only produces reinforcement when a particular stimulus is presented and typically there is only 1 response per trial

• rate of responding is determined by rate of presentation of the stimulus signaling the individual to respond

• dependent measure: percent correct

• typically there is an Intertrial Interval (ITI)

Ratio Schedules

• Fixed Ratio

• Ratio Strain

• Variable Ratio

• Progressive Ratio

Fixed Ratio

• reinforcement occurs after a set number of responses are made

  • produces a pattern of responding characterized by a postreinforcement pause (PRP) following reinforcement, then a high steady rate

  • higher the required number of responses the longer the PRP

  • produces high resistance to extinction

Fixed Ratio Example

• piece rate pay

  • $10 per every X units completed that pass quality control

Ratio Strain

• increase response requirement too quickly causes deterioration in responding; increase gradually to get a high ratio and maintain behaviour

Variable Ratio

• reinforcement occurs after a number of responses, but number varies from reinforcer to reinforcer

  • produces high steady rate of responding with no postreinforcement pause

  • number of responses required is unpredictable

  • Variable ratio can maintain behaviour at higher ratio values than Fixed ratio

  • Variable ratio has greater resistance to extinction than Fixed ratio

Variable Ratio Example

• video lottery terminal (VLT)

• asking for a date

• casting for fish

• telephone sales

Fixed Ratio vs Variable Ratio

• Fixed Ratio are more commonly used than Variable Ratio

• Fixed Ratio used to produce a high rate of responding when can count each response

Progressive Ratio

• like frequency ratio but the ratio increases after each reinforcement

  • will eventually reach a Break Point where responding stops

    • break points will vary from individual to individual

  • can use the break points to determine how potent a reinforcement is

    • the higher the break point the more potent the reinforcer

  • often used to evaluate the addictiveness of drugs

Interval Schedules

• fixed interval

• variable interval

Fixed Interval

• reinforcement is produced by the first response after a fixed interval of time has elapsed

  • response before interval has elapsed has no effect

  • responding increases as end of interval nears (scallop)

  • PRP, varies directly with duration of interval

Fixed Interval Examples

• passage of congressional bills

• turning on TV to view favorite soap opera

Variable Interval

• first response after an interval of time produces reinforcement (interval varies from reinforcer to reinforcer)

  • moderate steady rate of responding

  • non postreinforcement pause (interval duration unpredictable)

  • high resistance to extinction

    • but responding in extinction is less than with ratio schedules

Variable Interval Examples

• checking answering machine/e-mail for messages

  • hard to determine exactly when email will come in so people must check frequently

Interval vs Ratio

• in practice, interval schedules are less commonly used

  • fixed interval produces long postreinforcement pause

  • variable interval produces lower response rate than variable ratio

  • must monitor behaviour for first response after interval

Interval Schedules with Limited Hold

• short period of time after the interval from an interval schedule elapses during which a response will produce reinforcement

  • if the response does not occur during the limited hold, the reinforcer is lost

Fixed Interval with Limited Hold Example

• Fixed interval = 2 minutes, Limited Hold = 10 seconds

  • after the 2 minute interval has elapsed, the child must engage in the target behaviour within 10 seconds or else the reinforcer is lost and the next 2 minute interval begins

• Fixed interval = 2 hours, Limited Hold = 1 minute

  • bus arrives at the bus stop every 2 hours, but is only there for 1 minute before it leaves again

Limited Hold Schedules in Nature

• more common than basic schedules

Variable Interval with a Limited Hold

• produces responding similar to variable ratio schedule

• used to produce ratio-like responding using interval schedules

Ratio Schedule with Limited Hold

• like a deadline for meeting the response requirement for a schedule

  • limited window for response

Fixed Ratio with Limited Hold

• Fixed ratio = 30, Limited Hold = 2 minutes

  • for reinforcement to occur, 30 responses must occur within 2 minutes

    • if this is not met the reinforcer does not occur

Duration Schedules

• behaviour must occur continuously within a fixed or variable duration of time in order for a reinforcement to be produced

  • produce long periods of continuous behaviour

  • Fixed duration produces postreinforcement pause, variable duration does not

  • ex; hourly pay: 8 hour shift, play video games for 15 mins if study continuously for an hour

• used only when behaviour can be monitored continuously and reinforced based on its duration (ex; can’t continuously clean room but can continuously study)

Concurrent Schedules

• more than one schedule of reinforcement operates simultaneously and the individual can respond on any schedule and obtain reinforcement from any schedule

• allocation of behaviour follows the matching law

Matching Law

• “proportion of responses/time allocated to an alternative equals/matches the proportion of reinforcements obtained from that alternative”

• allocation also affected by type of schedule (conc variable interval, variable ratio), immediacy of reinforcement (smaller more immediate vs larger more delayed reinforcer), reinforcer magnitude, response effort

• more reinforcement from one schedule = more time spent following that schedule

*not necessarily the same in humans

Illustrative Study

• college students sat, one at a time, at a table with 3 confederates

• confederate directly across from participant kept conversation going

• 2 confederates to either side provided verbal statements of approval of the participant’s statements (“good point”, “i like that idea”)

• 1 confederate made these statements much more frequently than did the other

• relative proportion of time participants spent talking to the confederates matched the relative frequency of the statements of approval by those confederates

  • participant spent more time talking to the confederate that gave more reinforcement

Pitfalls

• inconsistency in the application of extinction shifts the schedule of reinforcement for an undesirable behaviour from continuous to intermittent

  • strengthens/increases the frequency of the undesirable behaviour (crying, whining, tantrums) — if you sometimes give in to tantrums and other times don’t