2. Transposition: Spence’s Behavioral Solution Transposition seems to support the cognitive view that organisms learn by discovering how things are related, like, “the darker of the two objects leads to food.” This implies that subjects compare the objects through some kind of mental process rather than look at each object separately. The traditional behavioral view is that an association is formed between a response and a specific stimulus; there is no comparison between stimuli.

3. Transposition: Spence’s Behavioral Solution How can the apparent transposition (transfer) of a relationship be explained without assuming that the subject sees a relationship? ?

4. Transposition: Spence’s Behavioral Solution Kenneth W. Spence developed a general theory of discrimination learning that not only explained transposition but revealed a shortcoming in cognitive theory. The theory used existing behavioral concepts: reinforcement, extinction, excitation, inhibition, and stimulus generalization.

5. Transposition: Spence’s Behavioral Solution Reinforcing a response to a stimulus increases the tendency to respond to that stimulus again. This tendency is called excitation. Reinforcement Extinction Not reinforcing a response to a stimulus decreases the tendency to respond to that stimulus again. This reduced tendency to respond is called inhibition.

6. Transposition: Spence’s Behavioral Solution After reinforcing a response to a stimulus, that response will tend to occur to similar stimuli. The greater the similarity, the stronger the response will be. Excitatory Stimulus Generalization

7. Transposition: Spence’s Behavioral Solution After extinguishing (not reinforcing) a response to a stimulus, that response will tend to be suppressed in the presence of similar stimuli. The greater the similarity, the strong the suppression will be. Inhibitory Stimulus Generalization

8. Transposition: Spence’s Behavioral Solution Let’s illustrate this process using a pigeon responding for food in an operant chamber: Excitatory Stimulus Generalization Pecks on the disk (or “key”) are reinforced on a VI schedule. The key is lit green.

9. Transposition: Spence’s Behavioral Solution We then put the pigeon on extinction (no food for pecking). Every minute, we change the color of the key. Excitatory Stimulus Generalization The bird will peck thousands of times without food. We count how many responses are made to each color.

10. Transposition: Spence’s Behavioral Solution Here is a graph that shows typical results: Excitatory Stimulus Generalization Wavelength Number of Responses

11. Transposition: Spence’s Behavioral Solution The pigeon receives discrimination training using the following stimuli: Inhibitory Stimulus Generalization Discriminative Stimulus: White Triangle on Gray Background; VI reinforcement schedule. Delta Stimulus: White Triangle on Blue Background; no food (extinction).

12. Transposition: Spence’s Behavioral Solution We keep switching back and forth: Inhibitory Stimulus Generalization The pigeons forms a discrimination, pecking a lot when the background is gray but pecking very little when the background is blue. Basically, “blue” means STOP.

13. Transposition: Spence’s Behavioral Solution Next, we put the pigeon on extinction—no food. The white triangle is projected on the key and we change the color of the background every minute. We count the number of pecks to the key in the presence of each color. Inhibitory Stimulus Generalization

14. Transposition: Spence’s Behavioral Solution Here is a graph that shows typical results: Inhibitory Stimulus Generalization Wavelength Number of Responses

15. Transposition: Spence’s Behavioral Solution Through stimulus generalization, the same stimulus may produce both excitation and inhibition. Will the subject respond or not respond to that stimulus? Spence assumed that the likelihood of responding could be estimated as follows: Application to Transposition Excitation - Inhibition Here are some examples. Suppose that we have measured the amount of excitation and inhibition produced by each stimulus. Which stimulus is more likely to produce a response?

16. Transposition: Spence’s Behavioral Solution Which Stimulus is More Likely to Produce a Response? Excitation = 7 Inhibition = 6 Excitation = 10 Inhibition = 4

17. Transposition: Spence’s Behavioral Solution Which Stimulus is More Likely to Produce a Response? Excitation = 10 Inhibition = 4 Excitation = 8 Inhibition = 1

18. Transposition: Spence’s Behavioral Solution Which Stimulus is More Likely to Produce a Response? Excitation = 8 Inhibition = 1 Excitation = 5 Inhibition = 0

19. Transposition: Spence’s Behavioral Solution The Transposition Experiment: Training Phase Excitation Inhibition or Brightness Dimension VS Which stimulus is more likely to produce a response?

20. Transposition: Spence’s Behavioral Solution The Transposition Experiment: Test Phase Excitation Inhibition or Brightness Dimension VS Which stimulus is more likely to produce a response?

21. Transposition: Spence’s Behavioral Solution The Transposition Experiment: New Test Phase Excitation Inhibition or Brightness Dimension VS Which stimulus is more likely to produce a response?

22. Transposition: Spence’s Behavioral Solution Spence’s theory predicts that if the test stimuli are far away from the training stimuli, transposition will break down. The subject will choose the lighter of the two stimuli. Surprising Prediction Cognitive theory predicts that the subject will continue to choose the darker of the two stimuli. Spence’s prediction is confirmed! Transposition breaks down. A big boost for the behaviorists!