Theories of Reinforcement

• Why is a reinforcer effective?

• Why do reinforcers increase the probability of a response?

Some Early Definitions

• Empirical: Stimuli that increase the probability of a preceding response are reinforcers– circular definition, after the fact– better, if shown to be trans-situational

• Theoretical: Reinforcers are stimuli that produce “a satisfying state of affairs”– vague

Drive Reduction Theory

• Organisms attempt to maintain physiological equilibrium (homeostasis)

• Deviations from homeostasis produce biological drives– examples: hunger, thirst, pain

• Reinforcers are events that reduce biological drives– examples: Kraft dinner for a hungry

undergraduate

Drive Reduction Theory

Amount of food in body

Compare with Set Point

Seek or don’t seek food

drives

But……………..

• Sensory reinforcers: Inquiring minds want to know

• Some reinforcers actually increase drive states

• Behavior itself might be reinforcing

Premack Principle

• Behaviors are reinforcing, not stimuli

• To predict what will be reinforcing, observe the baseline frequency of different behaviors

• Highly probable behaviors will reinforce less probable behaviors

Implications

• Reinforcers are individualized (not intrinsic to the reinforcer itself)

• Reinforcers are reversible

Some Problems With Premack’s Principle

• Quantification– Some activities naturally take more or less

time than others

• Opportunities to engage in a restricted (but not lower probability) behavior may act as a reinforcer

Newer View

• Timberlake’s Response deprivation hypothesis– reinforcers are responses that have been

“deprived”

Response deprivation hypothesis

.25 .5 .75

The ice cream scale (in pints)

1.0 1.25 1.5 1.75

2.0 2.25 2.5

Bliss point

(1.0 pint/night)

Will work to avoid ice creamWill work to obtain

Response Deprivation Hypothesis

• Low frequency behaviors can reinforce high frequency behaviors

• All behaviors have a preferred frequency or behavioral bliss point

• Deprivation below that frequency is aversive, and organisms will work to remedy this

Behavioral Regulation

• Measure time spent in behavior when there is no constraint– behavioral bliss point

• Schedule imposes a constraint– schedule line

• Time spent in behavior under a constraint will minimize distance from bliss point

The labor supply curve

Amount of Work

Am

ount

of

rew

ard

Blisspoint

2 rewards per unit 1 reward

per unit

¼ reward per unit