Psych 381 Ch 8

Stimulus Control

• Performing behaviours at appropriate times

• i.e., when certain stimuli are present

• For Example,

• Wear bikini to beach, not to class

• Forage when there is no predator, but not when there is a

predator

• Drink beer when you are at a bar, not at church service

How to Measure Stimulus Control

•How do we “ask” animals (or human infants) if two

stimuli are different from one another?

• Differential responding

• Stimulus discrimination

differential responding

• Variation in responding that corresponds to a variation in

stimuli

• Remember the habituation to visual patterns in infants?

stimulus discrimination

• Responding differentially to two or more stimuli

How to Measure Stimulus Control

• Reynolds (1961) Asked the question: “what is the pigeon paying attention to?”

• In other words, “what about this stimulus is controlling the responding by the pigeon?”

Research Example: Discrimination Task

• Stimulus discrimination: respond differentially to two

or more stimuli

• E.g., operant Go/no-go procedure

chickadee in box with sound of call: male call, are they responding the right way?

Stimulus Generalization

• Failure to discriminate between two similar stimuli

• e.g., Baby Albert generalized his response to anything that

was white, and furry (like the white furry rat he was

conditioned to fear)

• ex: chickadees: a NEW male call but still treated as a male call

Generalization Gradient

What if there was no stimulus control?

Measuring the Degree of Control

comparing discrimination and generalization

D=different responses

G=same responses for different stimuli

Factors in Stimulus Control

1. Sensory capacity

2. Orientation

3. Ease of conditioning (overshadowing)

4. Type of reinforcement

5. Type of response

1. Sensory Capacity

Stimulus control can ask questions about what animals perceive:

• Can an animal see colours?

• Train to discriminate between colours

• What is an animal’s hearing range?

• Train to discriminate between presence and absence of acoustic cue

Sensory Capacity Example

•Japanese quail and European starlings trained to

discriminate between two different visual stimuli

2. Orientation

• What are you looking at?

• Animal needs to be oriented towards the stimulus

3. Ease of conditioning (overshadowing)

•Interference with conditioning of a stimulus because of the simultaneous presence of another stimulus that is easier to condition

• Competition among stimuli for access to learning processes

•Higher intensity stimulus more easily conditioned

graph: overshadowing of tones by light

Overshadowing in Landmark Learning (Spetch, 1995)

• Pigeons & undergraduates

• Touch screen task to study landmark learning

• Tested for stimulus control of landmarks and potential factors controlling overshadowing

• Trained to peck or touch goal location, which was relative to different landmarks

• “Overshadow” (OV) landmark

always appeared with two other

landmarks

• A close one (CL)

• A far one (FAR)

• “Non-overshadowed” landmark

always appeared with only one

other landmark

• A far one (FAR)

How Do Animals Treat Compound Stimuli?

• Stimulus Elements vs. Configural Cues

• Stimulus-element approach

• configural-cue approach

• Stimulus-element approach

Organisms treat stimulus

elements as distinct and separate features of the

environment

• Configural-cue approach

Assumes that organisms treat

stimuli as integrated wholes

Not All Stimuli Are Discriminated Equivalently

• Some stimuli are more easily used as discriminative

stimuli than others

• For example, Training songbirds to discriminate

natural stimuli occurs more quickly than training with

synthetic stimuli

4. Type of reinforcement

effect of different reinforcers

•Degree of stimulus control also depends on the type

of reinforcement used

• Some stimuli work better when contingent with

positive reinforcement (APPETITIVE), others with

negative reinforcement (AVERSIVE)

• Foree and LoLordo (1973) tested this idea in pigeons...

Foree & LoLordo (1973)

• Belongingness & behavioural systems

• Food-activated feeding system

  • Visual cues “go” with food

• Shock-activated defense system

  • Auditory cues “go” with predators

5. Instrumental Response Factors

•Nature of the response required for reinforcement can

affect stimulus control

Quality-Location Effect

Dobrzecka et al. (1966), from Domjan (2010) Q: Which of two features would control behaviour?

• Quality of stimulus

  • Metronome or Buzzer

• Location of stimulus

  • In front or behind animal

Quality-Location Effect Test

positions of metronome and buzzer were reversed

Quality-Location Effect Predictions

• If quality of the stimulus was controlling behaviour; then

they will perform the behaviour that goes with each

sound, regardless of where the sound is located

• If location of stimulus was controlling behaviour, then it

should not matter what sound is in what spot

Quality-Location Effect Results

• Spatial responses (Left vs. right leg) come under the

control of spatial location of cue

•Quality responses (go/no-go) come under control of

the quality of the cue

Learning & Stimulus Control

• Can have Stimulus Discrimination Training in both classical and instrumental conditioning:

  • Classical Conditioning: CS+ or CS-

  • Instrumental Conditioning: S+ (SD) or S- (SΔ)

• Stimuli explicitly associated with other stimuli or outcomes

•Different views about why generalization exists...

• Pavlov: Generalization caused by similarity of a

stimulus to the original CS

• Lashley & Wade (1946): Generalization reflects the

absence of learning

Discrimination Training Effects on Stimulus Control

•Use generalization gradient to determine degree of

stimulus control

•Need to determine the feature(s) of the discrimination

procedure that controls the gradient

Jenkins & Harrison (1962)

• interdimensional discrimination (blue)

  • BETWEEN

  • tone vs no tone (like R vs L leg)

  • discrim within tones is not learned

• intradimensional discrimination

  • WITHIN

  • both tones BUT diff frequencies

  • faster discrim dropoffs cuz learning abt 1 stimulus

Range of Discriminative Stimuli

• Wide range of stimuli have been used in

discrimination studies

• Music, auditory frequencies, painting styles, geometric

shapes, medical slides, etc.

• We can use these discrimination studies to assess the

sensory capability of species

Can You Discriminate?

• picasso vs monet

• can pigeons?

• show novel images, shift other properties (ex: contrast, line weight, etc.) to see what they are attending to

• what if we introduce a new artist?

  • pigeons good as long as artists distinct enough from each other

  • base rule for generalizing & rule sets

Spence, and Discrimination Learning

• Spence (1936) thought that animals learned both

about S+s and S-s

• S+ = excitation

• S- = inhibition

•Different generalization gradients for different training

regimes

• Test with stimuli that vary systematically

•...we’re going to come back to this!

Hanson (1959): Results

• excitatory generalization gradient!

• intradimentsional discrimination

• very little responding to S+ wavelength

  • peak-shift effect!

Peak-Shift Schematic

What Spence thought:

• Excitation developed around the S+

• Inhibition developed around the S-

• Peak-shift was the net effect of these

two generalization gradients

Equivalence Training

•Opposite to discrimination training

• Train animals to treat dissimilar stimuli as similar –

Stimulus equivalence

• Train animals to generalize, not discriminate among

stimuli

The Big Picture: Contextual cues

• Male quail sexual conditioning (Akins, 1998)

• Arena with two compartments (OR ‘CONTEXTS’):

• Sand floor, orange walls & ceiling

• Wire-mesh floor, green walls & ceiling

• Individual subjects allowed to move back and forth in baseline

• Less preferred compartment made CS+

• Conditioning:

• Experimental group: CS+ paired with sexually receptive female (US)

• Control group: US only in home cage, never in CS+ compartment

Akins (1998): Results

came to prefer context that was associated with female!

Modulators overview

• Modulator: a third event (in addition to CS/US or

Response/Reinforcer)

• Assists in determination of the binary relation

• e.g., Context of rooms in male quail sexual conditioning

experiment

• e.g., S+s and S-s (discriminative stimuli) in operant

discrimination tasks are modulators

• Modulators are facilitators or occasion setters in

Pavlovian conditioning experiments

modulator

a third event (in addition to CS/US or

Response/Reinforcer)

• ex: population affects how a hockey team is supported whether they are winning or losing

conditional control

pavolvian conditioning

• light and no light are both antecendents

• no light: extinction stimulus bc it means no food

• light: discriminative stimulus bc it means food