Underlying Processes in Classical Conditioning

Theory

S-S vs. S-R Models of Conditioning

• S-S Learning = Stimulus-Stimulus• The CS becomes directly associated with the US

• Therefore, the CS comes to elicit a response that is similar / related to the US

• S-R Learning = Stimulus-Response• The CS becomes directly associated with the UR

• Therefore, the CS comes to elicit the same response as the UR

S-S vs. S-R Models

• The research conducted to test whether classical conditioning is based on S-S or S-R learning has found evidence to support both positions (not usually in the same study :)

• Currently, there tends to be a heavier emphasis on study of S-S associations

S-S Approaches

• One example is Pavlov’s stimulus-substitution theory– The CS acts as a substitute for the US

– A connection forms in the brain between the CS and the US activation sites

– When the CS is activated alone following acquisition, it will automatically activate the US site in the brain

– Therefore, the CR should be almost identical to the UR (because the connection between UCS and UR in the brain is hardwired)

Evidence in support of the stimulus substitution hypothesis

• Jenkins & Moore (1973) study:– Autoshaping in pigeons– One group had CS(light)-->US(grain)

• Photos showed pigeons trying to “eat” the lit key (open beak and closed eyes) when they pecked

– 2nd group had CS(light)-->US(water)• Photos showed pigeons trying to “drink” the

lit key (closed beak and open eyes) when they pecked

Jenkins & Moore (1973)Left = Water Right = Grain

Evidence against the stimulus substitution hypothesis

• Any study in which the elicited CR is different from the UCR

e.g., when a tone is paired with shock, rats will jump to the UCS (shock), but the CR is typically freezing

e.g., when a light is paired with food, rats will rear to the light (CR) but the UCR is approach to the food dispenser

Preparatory Response Model

• Kimble’s (1961, 1967) theory proposed that the CR is a response that serves to prepare the organism for the upcoming UCSe.g., following acquisition of CRs in eyeblink

conditioning, the CR eyeblink may actually prepare the person for the upcoming airpuff such that the eye would be partially closed when the airpuff occurs

Compensatory-Response Model

• The compensatory-response model is one version of preparatory-response theory

• In this model of classical conditioning, the compensatory after-effects to a US are what come to be elicited by the CS

• Based on the opponent-process theory of emotion / motivation

Opponent-Process Theory of Emotion (Solomon & Corbit, 1974)

• Emotional events elicit two competing processes:– The primary- or A-process that is immediately elicited

by the event• e.g., taking an exam elicits an unpleasant A-state

– An opponent- or B-process that is the opposite of the A-process and counteracts it

• e.g., the pain during the exam (A-state) creates a pleasant relief response (B-state) following the exam

Properties of the A and B processes

• A-process– magnitude &

duration of the A-state are determined by the stimulus event

– magnitude & duration are fixed (no change with experience)

• B-process– dynamic; changes with repeated

exposure– with repeated exposure the B-

state begins earlier, has greater magnitude, & lasts longer

– if time passes without exposure, the changes in the B-state reverse

– Changes due to repeated exposure depend upon short delays between presentations

Underlying Opponent Processes

Stimulus

a-state

b-state

Stimulus

a-state

b-state

• First few stimulations

• After several stimulations

Opponent-Process Theory of Emotion

• The actual emotional state of the organism is determined by the difference in magnitude between the 2 states:– The A-state minus the B-state = end emotional

result– If A-state > B-state, then the emotion

experienced will be A-like– If B-state > A-state, then the emotional result

will be B-like

Resultant Emotional State

Stimulus

a-state

b-state

Stimulus

a-state

b-state

• First few stimulations

• After many stimulations

Evidence for a Compensatory-Response Model

• Siegel (1972) gave rats repeated injections of Insulin – Insulin’s effects are to reduce the level of

glucose in the blood

• Tested by giving the rats an injection of saline (instead of insulin)– Measured the CR (change in blood glucose

levels)

Siegel (1972) Results

• There was a strong CR that occurred, but it was an INCREASE in blood glucose levels– (The opposite of Insulin’s direct effect)

• CR ≠ UR, and the CR was definitely compensatory

More Evidence in Support of the Compensatory-Response Model

• Conditioned morphine tolerance (Siegel, Hinson, & Frank, 1978)– Experimental Group: CS (light change &

noise reduction) paired with US (injection of morphine) for 9 days

– Unpaired Control Group– Placebo Control Group (CS paired with

injection of saline)

Siegel et al. Results (Conditioned Drug Tolerance)

0

5

10

15

20

25

30

35

40

45

Saline Paired Unpaired

Mea

n L

aten

cy t

o L

ick

Paw

• Test: present CS, inject every rat with morphine, & place each rat on a moderately hot surface– Measure latency to lick

their paws– The faster they lick,

the quicker they feel the pain

Challenges to the Compensatory-Response Model

• Eikelboom & Stewart (1982) found that the CR was much like the response to the drug itself (UR) with both opiates like morphine and with stimulants such as cocaine and d-amphetamine.

• It has been argued that conditioned tolerance effects could be due to habituation of the direct A-process rather than being due to classical conditioning of the opponent B-process.