1. Spontaneous Recovery A Skinnerian interpretation: By Jack Michael

2. Pigeon Operant Chamber Rfmt unavailable: aperture light off, grain hopper down where grain cannot be accessed. food aperture grain hopper down food aperture aperture light pecking key key lights

3. Pigeon Operant Chamber Rfmt available: aperture light on, grain hopper up. After 3 sec, light goes off and hopper goes back down. food aperture grain hopper up food aperture aperture light pecking key key lights

4. Pigeon Operant Chamber food aperture grain hopper food aperture aperture light pecking key key lights Rfmt unavailable: aperture light off, grain hopper down where grain cannot be accessed.

5. 30 min extinction sessions 0 30 minutes Day 1 Day 2 Day 3 Response rate at the start of extinction session 2 is greater than at the end of ext. session 1. And greater at the start of extinction session 3 than at end of extinction session 2. And so on. responses end of extinction session 1 end of extinction session 2 start of extinction session 2 start of extinction session 3 Spontaneous Recovery: What is it?

6. *For a thorough treatment of spontaneous recovery and its relation to the concept of inhibition see Catania, 1998. 30 min extinction sessions 0 30 minutes responses Day 1 Day 2 Day 3 Spontaneous Recovery (cont'd.) Why does it happen? Skinner offers another explanation based on operant stimulus control. (Skinner, 1950, p. 85) Some theories (Pavlov, Hull, others) contended that responding without reinforce- ment generates a form of inhibition* (an hypothesized neurochemical substance, or a hypothetical entity of some sort), but with the passage of time this entity dissipates. *

7. Stimulus Change Decrement: After an operant function-altering operation (reinforcement, extinction, punishment, recovery from punishment, and others), the changed function is seen at its maximum value when the stimulus conditions are exactly the same as during the function-altering operation. Any change from those conditions results in a decrement in the changed function. When the changed function is an increase in responding due to reinforcement, then a stimulus change results in less behavior than if the stimuli were the same as during reinforcement. When the changed function is a decrease due to extinction or punishment, then a stimulus change results in more behavior than if the stimuli were the same as during extinction or punishment.

8. Nine pigeons were given a history of variable ratio (VR) reinforcement for pecking a yellow triangle. In the session at right the triangle is yellow for the first 30 minutes with more than 1100 rsps per bird*. When extinction starts key color is changed to red. After 15 minutes the color was changed back to yellow. Demonstration of stimulus change decrement with respect to extinction *Group data: Curve is based on the responses for all 9 birds. VR rfmt extinction responses 1800 0 time in minutes 60

9. Phase 1: Pigeon is placed in the experimental chamber with red ceiling light flashing, but the light fades to off in 2 minutes. Key pecking gets VI 30 sec rfmt in presence and absence of the flashing red light. Spontaneous recovery analogy: A hypothetical experiment that is more like the actual spontaneous recovery situation 300 010time in minutes responses VI 30" Rfmt intensity of flashing red light bright off flashing light on but fading to off in 2 min flashing light off 010time in minutes

10. Phase 2: Ext. session, with flashing red light on at the beginning of the session but fades rapidly to off in 2 min, as during reinforcement sessions. There is thus only 2 min extinction in flashing light before it goes off, then about 8 min ext. with light off. Then after 10 minutes flashing light is turned on. Responding recovers as in Skinner's procedure. Spontaneous recovery analogy (cont'd.)

11. At the beginning of reinforce- ment sessions there are residual stimulus effects from being removed from the home cage, transported to the experimental chamber, etc. These rapidly fade to off just like the flashing red light in the hypothetical experiment. Spontaneous recovery analogy (cont'd.) During an extinction session there is only a small extinction history in the presence of the residuals of handling stimuli. There is much more extinction in the absence of these stimuli. Thus more behavior occurs when they are again present at the beginning of the next ext. session than were occurring at the end of the previous ext. session in their absence.

12. Somewhat controversial. Some studies (e.g. Welker & McAuley, 1978) support Skinner's interpretation but some (e.g. Thomas & Sherman, 1986) do not. But the analysis illustrates Skinner's broad interpretation of the stimulus, and his concern for environment-behavior details. How About "Late" Spontaneous Recovery? Pigeons were given 1-hour reinforcement sessions, then very brief extinction sessions, until no responding occurred in the brief sessions. Then when a session lasted the usual duration, responding occurred in the later part of the session. Extinction had occurred in the presence of the stimuli of having just been placed in the chamber, but there had been no extinction in the presence of stimuli consisting of having been in the chamber for a while. (Kendall,1965). Spontaneous Recovery (still cont'd.)