Chapter 8 – Stimulus Control of Behavior Outline 1 –Identification and Measurement of Stimulus Control Differential Responding and Stimulus Control Stimulus Generalization Stimulus Generalization Gradients as Measures of Stimulus Control –Stimulus and Response Factors in Stimulus Control Sensory Capacity and Orientation Relative Ease of Conditioning Various Stimuli Type of Reinforcement Types of Instrumental Response

The concept of behavioral control –S (stimulus) Can elicit responding (R) Can create expectancies (O) “Appropriate behavior” is often controlled by cues (stimuli) in our environment. –Get undressed for bed –Get undressed at school –Kiss girlfriend/boyfriend –Kiss random person walking on campus This chapter considers how stimuli come to control our behavior.

Identification and Measurement of Stimulus Control –How do we know that a behavior is under stimulus control? Consider Reynolds (1961) –Train pigeons to peck a white triangle on a red background. VI schedule –Elicited steady pecking –Test with red key (no triangle) –Or white triangle (no red; background is black)

Stimulus Generalization –How specific is stimulus control? Early researchers (like Pavlov) examined this question. Guttman and Kalish (1956) –Train VI schedule S+ = 580nm light (yellowish orange). –Test Different colors –520 nm (green) –540 nm –550 nm –570 nm (yellow) –580 nm (yellowish orange) –590 nm (orange) –600 nm –620 nm –640 nm (red Random order In extinction

Generalization Gradient

The generalization gradient indicates stimulus control by color. –It is somewhat specific for the training stimulus. But generalizes to similar colors. There is no gradient for the hypothetically color blind pigeons –Color does not control responding.

What determines the degree of stimulus control obtained? Stimulus and Response Factors –Sensory Capacity and orientation Must be able to sense it –Rats don’t do well with color stimuli –They do very well with odor stimuli. Horse study from book. –Trained to select color over gray. »Push lever with head. »85% correct »All 4 picked blue and yellow over gray »3 picked green over gray »Only 1 picked red over grey »Implies they may have poor red sensation

Relative ease of conditioning various stimuli. –Whether a stimulus exerts control depends on whether it stands out from other cues in the environment –Children’s book Big pictures Smaller words –Overshadowing (first noticed by Pavlov) CS 1 – loud sound CS 2 – dim light More conditioning occurred to the stronger stimulus –Conditioning was better for CS 2 if presented alone –Overshadowed by CS 1 if presented together

Type of Reinforcement –Aversive vs. Appetitive seems to matter Foree and LoLordo (1973) –Two groups of pigeons –Both were trained to respond when presented with a compound discriminative stimulus Red light and tone –Group 1 Step on treadle to gain food –Group 2 Step on treadle to avoid shock –Test both groups with Red light alone Tone alone

Visual stimuli tend to gain control over appetitive stimuli Auditory stimuli tend to gain control over aversive stimuli. Behavior systems? –Food RF activates feeding system? Rats and pigeons are more likely to find food with vision rather than hearing. –Shock RF activates defensive system? Auditory cues may be particularly adaptive for avoiding danger.

Outline 2 –Learning Factors in Stimulus Control Stimulus Discrimination Training Effects of Discrimination Training on Stimulus Control What is Leaned in Discrimination Training? Interactions Between S+ and S-: Peak Shift Effect Range of Possible Discriminative Stimuli Stimulus Equivalence Training –Contextual Cues and Conditional Relations Conditioned Place Preference

Learning Factors in Stimulus Control –left to their own devices animals come under stimulus control based on the stimulus and response factors discussed above. –But can we train animals to make finer distinctions?

Stimulus Discrimination Training. –Let’s go back to the color generalization study –Train VI schedule S+ = 580nm light (yellowish orange). –Test Different colors –520 nm (green) –540 nm –550 nm –570 nm (yellow) –580 nm (yellowish orange) –590 nm (orange) –600 nm –620 nm –640 nm (red Random order In extinction

Generalization Gradient

Note that the pigeons treated the 590 nm stimulus nearly the same as the 580 nm Can they tell the difference? How could we find out?

Train with two stimuli. –In operant conditioning we call them S+ (S d ) and S- (S ∆ ) S+ responding will result in RF S- responding will have no effect –Pavlovian CS+ (CS-US) CS- (CS- no US) For our color discrimination –S+ = 580 nm –S- = 590 nm

Hypothetical Result

Effects of Discrimination on Stimulus control –Increased stimulus control 1) Discrimination narrows the generalization curve 2) Discrimination within a dimension narrows it even more –Makes the relevant dimension clear? »Tone vs. loudness Example: Jenkins and Harrison (1962) –Trained with tones 3 groups –1) generalization »S cps tone –2) discrimination »S cps tone »S- no tone –2) within discrimination »S cps tone »S- 950 cps tone

What is learned in Discrimination Training? –Example S+ (light) S- (tone) 1) learn about S+ alone –Respond during light –Learn nothing about tone 2) learn about S- alone –Suppress responding during tone Learn nothing about light 3) learn about both (Spence’s Theory) –Respond during light –Suppress responding during tone

Spence’s Theory of Discrimination Learning –The S+ becomes excitatory Signals RF –The S- becomes inhibitory Signals lack of RF How do we test this? –Responding to S+ and not responding during S- is not enough Any of the 3 theories predict this

The peak shift can be considered evidence for Spence’s view.

Range of Possible Discriminative Stimuli –Many kinds of stimuli have been examined Simple –Color –Tone Complex –Number –Time of day –Kind of music »Carp »Blues vs. Classical »John Lee Hooker vs. Bach

Types of Stimuli continued –Artists Monet vs. Picasso –Internal Hunger Drugs

–Cocaine = left lever –Saline = right lever Antagonist? Other drugs? –Amphetamine? –Caffeine?

Stimulus Equivalence Training –We have seen that discrimination can sharpen stimulus control Treat similar stimuli differently –Can we produce the opposite effect. Train animals to treat very different stimuli similarly?

Honey and Hall (1989) Group 1Group 2 Phase 1Noise = FoodNoise = nothing Clicker = FoodClicker = Food Phase 2Noise= foot shock Noise = Foot shock Test ClickerClicker Which group is more afraid of the clicker? –Group 1 Seems a common outcome causes the rats to treat the stimuli similarly.

Common Coding – a typical equivalence experiment –Based on Urcuioli, Zentall, Jackson-Smith, and Steirn (1989) Phase 1 (Many-to-One Matching-to- Sample) R  R+G- V  R+G- G  G+R- H  G+R- Phase 2 (new comparisons) R  B+Y- G  Y+ B- Test (does learning transfer)? V  B Y? H  Y B?

Does Equivalence training cause stimuli to become harder to discriminate? –Based on Kaiser, Sherburne, Steirn, and Zentall (1997) Train R  R+G- V  R+G- G  G+R- H  G+R- Test (discrimination) ConsistentInconsistent R+R+ V+V- G-G- H-H+ Which Group learns faster? –pecks S+ 90% of the time

Sidman –True equivalence must demonstrate three concepts 1) Reflexivity (sameness) –If A = A, B = B, C = C, and so on. 2) Symmetry (bidirectional equivalence) –If A = B then B = A 3) Transitivity (transfer equivalence across stimuli) –If A = B and B = C then A = C

Spoken and written speech involves these three aspects of equivalence. Reflexivity (sameness) –Apple = Apple –Orange = Orange = =

Symmetry (bidirectional equivalence) –A(object) = B (word) –B (word) = A (object) = Apple Apple =

Transitivity. –If A (object) = B (spoken word) –And B (spoken word) = C (written word) –Then A (object) = C (written word) If = And = Apple Then = Apple

Some have argued stimulus equivalence is a human trait –Requires language People with good verbal skills can form equivalent relationships easily. Those without have much more difficulty. Animals?

Reflexivity (sameness) –Pick the thing that looks the same Based on Zentall and Hogan (1978) Train (Identity matching-to-sample) –R  R+G- –G  G+R- Test (with “novel” stimuli) –B  B Y –Y  Y B

Symmetry (bidirectional equivalence) –Based on Zentall, Sherburne, and Steirn (1992) If red = food, then food = red If green = no food, then no food = green Train (differential outcomes procedure) –R  R+G- (food) –G  G+R- (noFood) do over until correct to move on Test –Food  R G? –No Food  G R?

Transitivity –Based on Steirn, Jackson-Smith and Zentall (1991) Phase 1 (Differential Outcomes) –R  R+ G- (food) –G  G+ R- (no food) Phase 2 –food  B+ W- –no food  W+ B- Test –R  B W? –G  B W?

Train (Differential Outcomes) Phase 1 –R  R+ G- (food) –G  G+ R- (no food) Phase 2 –food  B+ W- –no food  W+ B- Test –R  B W? –G  B W?

Contextual Cues and Conditional Relations –Conditioned Place Preference

Inject Rat with drug and confine to one side of chamber Test later (next day) –Drug free –Which side do they prefer?

Heroin – Good sick? Two groups of Thirsty Rats –Morphine Group Inject with morphine Place in Side 1 with Sacch. –Control Inject with Saline Place in Side1 with Sacch.

Test –open access –two bottles in each side Sacch vs. Water Results –Morphine Group? More time in Side 1 avoid Sacch. –Control? Equal time each side prefer Sacch.