Stimulus Control of Behaviour

Stimulus Control Differential responding and stimulus discrimination Complex environment “Signal” from the “noise” What is important?

Reynolds (1961) Pigeons, operant chamber, compound key Train Test Responses per minute Bird 107Bird 105 trianglecircle

Discrimination and Generalization Differential responding –Stimulus discrimination Similar responding –Stimulus generalization

Generalization Gradients Train on one (or more) stimulus Test on continuum (i.e., a “gradient”) of other, related stimuli Plot on graph… Generalization Gradient Tricky –Reinforcement problem –Extinction problem –Probe trials and extinction blocks

Gen. Grad.: Stimulus Control Training stimulus Responses Stimulus Continuum (e.g., wavelength of light)

Gen. Grad: No Stimulus Control Training stimulus Responses Stimulus Continuum (e.g., wavelength of light)

Spetch & Mondloch (1993) Pigeons in localization task Touch-screen Peck at target area of 2cm 2 Target defined by landmarks Tested to determine the landmarks that controlled the discrimination

Training Stimuli

Results: Pigeon C207

Results: Pigeon 271

Factors in Stimulus Control

Sensory Capacity Organism’s sensory capacity determines what stimuli can control behaviour E.g., ultraviolet stimuli for honeybee, but not for human Physical orientation

Overshadowing Competition among stimuli for access to learning processes Higher intensity stimulus more easily conditioned Speed of conditioning

However… Stimulus element approach –Elements in a compound stimulus treated as distinct and separate components –Overshadowing: most salient stimulus gains control Configural-cue approach –Compound stimulus treated as an integral whole –Overshadowing: generaliztion decrement

Configural-cue interpretation –Overshadowing due to degrees of generalization decrement from training to testing –No generalization decrement for control group –Overshadowing group learned weak-STRONG, but only tested on weak, so considerable generalization decrement Evidence for both stimulus element and configural-cue approaches GroupTraining stimuliTest stimulusGeneralization from training to test Overshadowingweak-STRONGweakDecrement Controlweak No decrement

Type of Reinforcement Biological predispositions; belongingness Species Sometimes seasonal –E.g., stimuli associated with courtship disregarded outside of mating season

Force & LoLordo (1973) Training: Group 1 –L/T … press pedal … food Group 2 –L/T … press pedal … avoid shock Test compound and individual components Group1 (food reinforcer) Group 2 (shock avoidance) Tone & light Light Tone Pedal Presses

Instrumental Response Factors Nature of the response required for reinforcement can affect stimulus control

Dobrzecka, Szwejkowska & Konorski (1966)

Learning Factors in Stimulus Control Pavlov –Inherent properties of nervous sytem –Innate –Due to physical similarity of stimuli Lashley & Wade (1946) –Explicit discrimination training required –Stimulus control learned –Stimulus generalization because animals have NOT learned the difference between stimuli

Stimulus Discrimination Training In classical or instrumental conditioning –CS+ or CS-, S+ or S- Stimuli explicitly associated with other stimuli or outcomes Cummulative responses Time S+ S-

Training and 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)

Range of Discriminative Stimuli Wide range of stimuli have been used in discrimination studies –Music, auditory frequencies, painting styles, geometric shapes, etc., etc. Can use these discrimination studies to assess the sensory capability of species

Pigeon Art Appreciation Watanabe et al. (1995) Trained pigeons to discriminate between Monet and Picasso Achieved high degree of accuracy Pigeons generalized to other artists of the same style (Impressionist or Cubist)

What’s Learned Spence’s (1936) theory Learn about both S+ and S- –Stimuli treated separately S+ represents excitation S- represents inhibition Test –Excitatory stimulus generalization gradient Most response near S+ –Inhibitory stimulus generalization gradient Least response near S-

Honig et al. (1963)

S+/S- Interactions Interactions likely to occur between S+ and S- Especially likely if using intradimensional discrimination –Stimuli from same stimulus continuum Example seen in peak shift

Peak Shift Maximum responding on generalization gradient not to trained stimulus With S+/S- training Already seen in Jenkins & Harrison (1962) Peak shift

Hanson (1959

Spence’s Interpretation Opponent process system S+ generates internal excitatory gradient S- generates internal inhibitory gradient Actual generalization gradient (i.e., measured behavioural response) due to net sum of excitatory and inhibitory gradients

S+S- excitatory inhibitory Hypothetical internal gradients e.g., responses Actual generalization gradient (i.e., net sum) Stimulus continuum

Absolute/Relative Control Absolute interpretations –Learn specifics of individual stimuli –Spence’s theory is an absolute theory Relational interpretatsions –Learn relationship between stimuli

Transposition Task Kohler (1939) Can a relational rule be transferred to a new stimuli set? Testing Training S+S- transfer (relational) absolute

Intermediate Size Problem Gonzales, Gentry & Bitterman (1954) Chimpanzees, visual display of squares Chimps choose intermediate size on transfer test S+ TrainingTransfer Test

Training Technique Simultaneous discrimination training –S+ and S- presented together Successive discrimination training –S+ and S- presented alone on different trials Relative stimulus control with simultaneous Absolute stimulus control with successive

Stimulus Equivalence Training Train subjects to treat dissimilar stimuli as similar Training to generalize, not discriminate Categorization learning

Herrnstein, Loveland & Cable (1976) Pigeons Presence/absence pictures S+: item present S-: item absent Various S+ stimuli: water, trees, people

Stimuli for Water as S+ Condition S-S+

Results Trees Water People

Contextual Cues Context cues can exert stimulus control Perform behaviours appropriate to a given context

Siegel (1975) Morphine tolerance Home room and injection room Same amount of morphine across 4 days Conditional compensatory response to context cues of injection room

Perkins & Weyant (1958) Two groups of rats run through two mazes, one white, one black; same maze layout Half of each group tested in same colour maze, half in opposite colour maze Poor performance for rats tested in opposite compared to same

Kamin (1957) State-dependent learning Rats; avoidance learning Test at various retention intervals Rats’ own internal physiology serves as context cue Avoidance (%) Retention Interval (hr)

Akins (1985) Male quail sexual conditioning Arena with two compartments –Sand floor, orange walls –Wire-mesh floor and walls, green 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

Results 1 23 Preference Tests % time spent in CS+ compartment Experimental Control

Conditional Relations Binary relations: between two events (CS-US, operant-outcome) Modulator: a third event that determines the nature of a binary relation Modulator signals a conditional relation

Modulators Instrumental –S+: respond --> reinforcer –S-: respond --> no reinforcer Classical –“Facilitators” or “occasion setters”, not excitatory or inhibitory conditional stimuli –CS = noise, US = food, modulator = light light noise food light noise food