Theories of Reinforcement List of known reinforcers would be endless The main issue: why are certain events effective as reinforcers? Two broad categories of answers: 1) Stimulus-intrinsic theories 2) Response-intrinsic theories 1. Stimulus-intrinsic theories a) Thorndike’s Law of Effect -circular b) Hull’s Drive-reduction theory -similar to Pavlov’s biological strength -includes the concept of homeostatic imbalance (drive) when deprived -evidence not supportive: -many reinforcers do not appear to reduce drive (saccharin, opportunity to mate) -some reinforcers not even tied to a physical stimulus (opportunity to play, novel environment, see a movie) -could postulate new drives, but now that list is infinite as well

c) Brain Stimulation theory Olds & Milner (1954) accidentally discover “pleasure centres” -very powerful reinforcer: animals will work until they drop from exhaustion -maybe this is what all reinforcers have in common…. Problems with this notion: -must prime subjects, even well-trained ones -extinction curve too sharp -could argue that the differences due to the activation strength, pathways -lots of work still being carried out using ESB as reinforcer

2) Response-intrinsic theories -general view is that it is not the reinforcer, but the behavior one engages in with the reinforcer that is reinforcing (e.g. car) -homeostasis as a behavioral state a) Premack Principle -prior to him, responses classified as R or Rfer based on either “consummatory” or “instrumental” nature -Premack denied this distinction, saying instead that the distinction is based on their baseline frequencies/durations of occurrence -given two responses arranged in an operant conditioning procedure, the more probable response will reinforce the less probable response, not the other way around -reinforcing ability is measured by an increase in the response in question -e.g. eating reinforces bar-pressing because if unconstrained, hungry rat more likely to eat -measure baseline engagement time, can then decide what will reinforce what e.g.: if unconstrained, rats will spend 70% of its time running, 10% drinking -so, if unconstrained, running can be used as a reinforcer for drinking behavior -drink -- run -see drinking behavior go up

Example with humans: -children offered opportunity to either eat candy or play pinball -some preferred one, some preferred the other -then set up a contingency: in one condition, children had to eat a certain amount of candy to engage in opportunity to play pinball -children that had high baseline preference for pinball increased the amount of candy they ate -then, reversed the contingency: children now had to play pinball a certain amount of time to receive candy -now, children that had a high baseline preference for eating candy increased their pinball-playing -in theory, depriving could result in turning anything into a reinforcer, provided the deprivation is below baseline for long enough (bread pudding) -Premack principle very useful in applied settings -punishment, deprivation not allowed in schools -traditional consummatory reinforcers not reinforcing to many clients -with Premack principle, simply use a more-probable behavior to reinforce a less-probable one -children given opportunity to run and shout after sitting quietly for a specified amount of time Problems with Premack: -time spent on a behavior sometimes fuzzy -some behaviors don’t take much time, but are highly valued; other behaviors take lots of time without much value

Response deprivation: addendum to Premack -responses will increase in “value” if deprived of opportunity to engage in them i.e.: remember the original example with the drinking/running? (running reinforces drinking behavior) - Can reverse the contingency with deprivation: water-deprived rats will run more than baseline in order to have opportunity to drink (run – drink) -any time you carry out an instrumental experiment, you are necessarily depriving organisms of some reinforcers until they perform the appropriate behavior -these deprived responses will act as reinforcers only when the deprivation schedule falls below the baseline level of performing the activity -for some very low-level behaviors, this can take a while, since baseline is virtually zero to begin with (bread pudding example) -all of the above is formally outlined in:

Bliss-Point theory It is a highly comprehensive mathematical treatment Postulates that there is nothing intrinsic to the reinforcer that provides reinforcement. Rather, an instrumental contingency causes a restructuring of activities in the client. In an unconstrained situation:“behavioral bliss” achievable e.g. drink 10 sec for 5 sec of running bliss e.g.: run 15 sec, drink 15 sec drinking e.g. run 10 sec, for 5 sec of drinking -must run more than they want to in order to achieve drinking ‘bliss’ running