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)• CS1 – loud sound• CS2 – dim light• More conditioning occurred to the stronger stimulus

– Conditioning was better for CS2 if presented alone– Overshadowed by CS1 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+ (Sd) 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+ 1000-cps tone– 2) discrimination

» S+ 1000-cps tone» S- no tone

– 2) within discrimination» S+ 1000-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

• 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 1 Group 2

• Phase 1 Noise = Food Noise = nothing

Clicker = Food Clicker = Food

 • Phase 2 Noise= foot shock Noise = Foot

shock

 • Test Clicker Clicker

• 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)• Consistent Inconsistent• 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.