Stimulus Control of Behavior Notes

Stimulus Control of Behavior

  • Behaviors are controlled by environmental stimuli.
  • In the wild, survival depends on adjusting behavior to environmental changes.

Stimulus Control

  • Organism is under stimulus control when behavior is determined by the stimulus.
  • Reynolds (1961) showed that it is not always clear what stimulus controls instrumental behavior.
  • Pigeons displayed differential responding, showing stimulus discrimination.

Stimulus Generalization

  • Occurs when an animal responds similarly to two or more stimuli.
  • Pavlov discovered stimulus generalization; animals responded to tones of similar frequency after training with a specific tone.

Measuring Stimulus Control

  • Stimulus generalization gradients measure stimulus control and reflect sensitivity to stimulus changes.
  • Guttman & Kalish (1956) conducted early studies on stimulus generalization.
  • The stimulus with the greatest control evokes the largest response during testing.
  • Discriminative stimulus (SD) is a stimulus that has gained control of instrumental responding.

No Stimulus Control

  • A flat gradient occurs when an organism responds similarly to all stimuli.

Factors in Stimulus Control

  • Pavlov discovered that an animal learns about the more salient stimulus when two stimuli are presented at the same time.
  • Overshadowing: A more salient stimulus prevents conditioning to a less salient one.
  • Stimulus control is influenced by the type of reinforcement.
    • Light easily associates with food reward
    • Tone easily associates with shock avoidance.

Instrumental Repsonse

  • Stimulus control depends on the type of response.
  • Dobrzecka, Szwejkowska, & Konorski (1966) showed responses differentiated by location are controlled by spatial features, and those differentiated by quality are controlled by the quality of stimuli.

Stimulus Discrimination Training

  • Stimulus control depends largely on an animal's learning experiences.
  • Stimulus discrimination procedures effectively bring behavior under control of a stimulus.
  • Campolattaro, Schnitker, and Freeman (2008) trained rats on eyeblink conditioning.
    • A+ paired with shock, B- was not.
    • Blinking behavior fell under control of A+.

Instrumental Conditioning

  • Stimulus discrimination training establishes stimulus control.
  • Rats learn to press a lever with one stimulus but not another.
  • Pigeons learn to peck to one color but not another.

Discrimination Training

  • Jenkins and Harrison (1960, 1962) researched pigeons pecking for food reinforcement.
    • Group 1: Reinforced for pecking to a 1000 Hz (S+) tone but not for pecking to a 950 Hz tone (S-).
    • Group 2: Reinforced for pecking to a 1000 Hz (S+) tone but not for pecking during absence of tone (S-).
    • Group 3: Reinforced anytime it pecked and a 1000 Hz tone was always on. THIS GROUP WAS NOT DISCRIMINATING.
  • Stimulus control is greatest when S+ and S- vary along the same stimulus dimension.

Interoceptive Cues

  • Schall et al. (1996) showed animals discriminate between internal sensations from drug states.
    • Phase 1: Pigeons injected with 3.0 mg/kg cocaine prior to session in which pecking was reinforced on a VI 2 min schedule.
    • Phase 2: Pecking was reinforced on drug- injected sessions (3.0 mg/kg ) but not on non- drug sessions.
      • A (3 mg/kg) Cocaine-Induced State Served As The S+.
      • A Non-Drugged State Served As The S-.

Compound Stimuli

  • Stimulus-element approach: Stimuli are perceived as distinct and separate.
  • Configural-cue approach: Organisms treat complex stimuli as indivisible wholes.

Configural Cues

  • Rats discriminate between configural cues and separate stimulus elements.
    • AB+ A-/B- C+/D+ CD-
  • Positive and Negative Patterning - Control of Behavior by Configural Cues

Discrimination Training Learning

  • Possible behavioral strategies:
    • Respond whenever S+ is present, regardless of S-.
    • Do not respond when S- is present, regardless of S+.
    • Respond only when S+ is present and not when S- is present.

Spence’s Theory of Discrimination Learning

  • Kenneth Spence (1936) believed animals learn about both S+ and S-.
  • Animals acquire excitatory tendencies to S+ and inhibitory tendencies to S-.

Excitatory and Inhibitory

  • Honig, Boneau, Burstein, & Pennypacker, (1963) Group 1: Reinforced for pecking when response key was illuminated with a white light and black vertical bar (S+). Not reinforced when key illuminated with a white light and no bar (S-).

S- Inhibition

  • The summation test demonstrates that S- acquires active inhibitory properties.
  • Kearns et al. (2005) studied lever pressing in rats with intravenous doses of cocaine used as reinforcement.
    • Experimental Group: Tone, Clicker: Reinforcement; Light: No Reinforcement
    • Control Group: Tone, Clicker: Reinforcement; Light: presented half the time with clicker (and reinforcement) and half the time alone (with no reinforcement)
    • The Light Inhibited Lever Pressing For the Experimental Group
  • This is just differential inhibition!

S+ and S-

  • Sometimes S+ learning influences responding to S-.
  • Occurs in intradimensional discriminations (S+ and S- differ on one stimulus feature).
  • Hanson (1959) studied discrimination in pigeons.
  • All Groups were reinforcement for pecking with a key light of 550 nm (S+).
    • Group 1: S- was a color of 590-nm wavelength.
    • Group 2: S- was a color of 555-nm wavelength.
    • Group 3: Control group – No S-. Just rewarded during S+.
  • Peak Shifts Can Occur With Any Intradimensional Discriminations When S+ and S- Are Similar

Spence Peak-Shift

  • Spence (1937) predicted the peak-shift phenomenon.
  • Generalized inhibition from S- suppresses responding to S+.
  • Peak shifts are less likely when S+ and S- are further apart.

Stimulus Equivalence Training

  • Has the opposite effect of discrimination training, promoting greater generalization.
  • Subjects are trained to treat similar stimuli equivalently.
  • Pigeons can be trained to respond similarly to different photographs, all of which contain water, and they can also learn to respond similarly to photographs containing human beings in them.
  • This represents a form of categorical learning.

Stimulus Equivalence Training

  • Stimulus equivalence training can be established by linking two stimuli to a common third event, like a food stimulus.
  • Honey and Hall (1989) performed the following experiment
    • Phase 1: Experimental Group
      • Noise– Food
      • Clicker – Food
    • Phase 1: Control Group
      • Clicker – Food
    • Phase 2: All Groups
      • Noise—Shock

Contextual Control

  • Behavior can come under the control of contextual cues.
  • Akins (1998) demonstrated this in male domesticated quail.
  • Exp Group: Birds were placed in CS compartment for 5 minutes. A sexually-receptive female was then placed in compartment for another 5 minutes. CS (compartment) – US (sex) paired.

Conditional Relations

  • Contextual cues do not have to signal reinforcement to gain control over behavior.
  • Thomas, McKelvie, & Mah (1985) trained birds in two different contexts (lighting and type of noise).
  • The S+/S- contingencies were reversed between the two contexts.

Pavlovian Conditioning

  • Establishing a conditional relation in classical conditioning requires introducing a modulator that indicates when a CS will be followed by reinforcement.
  • Rescorla, Durlach & Grau (1985) used Noise as a modulator for pigeons pecking an illuminated orange key light.
  • If Noise: Light – Food
  • If No Noise: Light – No Food

Conditional Control

  • Fetsko, Stebbins, Gallagher, & Colwill (2005) studied occasion setting in mice.
  • Whenever a light stimulus (modulator) was present, a noise stimulus would be followed by food.
  • Mice showed much more conditioned responding on trials that included the light.
  • The light, by itself, did not develop excitatory conditioning properties.

Conditional Control in Pavlovian Conditioning

  • Occasion Setting Light indicates US is coming
  • Conditioned Inhibition Light (CS-) indicates US is not coming
  • The procedure for occasion setting is the converse of the standard procedure for conditioned inhibition.