Behaviour Controlled by Aversive Stimuli Flashcards
Which of the following involve stimuli that people would likely describe as “aversive” or say that they did not like?
NEGATIVE REINFORCEMENT AND POSITIVE PUNISHMENT
Negative Reinforcement Examples:
Panadol escapes headaches
Giving bottle escapes crying
Holding rail avoids falling
Two types of Negative Reinforcement
(1) Escape
Remove aversive stimulus…
(2) Avoidance
Prevent aversive stimulus…
e.g., escape (take paracetamol to escape a headache) and avoidance (take daily medication to avoid getting sick at all)
responding occurs in presence of the aversive stimulus
E.g. putting on your coat outside
responding occurs in absence of the aversive stimulus
E.g. putting on your coat inside
Solomon and Wynne (1953)
Basic Procedure: light off > 10s > mild shock
First learn to escape: light off > 10s > mild shock > jump over > escape (remove aversive stimulus)
Then learn to avoid: light off > jump over (response occur in absence of aversive stimulus) = prevent aversive stimulus (shock)
Dog could escape from shock by jumping over barrier, avoid shock by jumping over barrier before ten seconds of darkness had elapsed
US = shock
UR = fear.
Fear is transferred from the US (shock) to CS (10 secs of darkness that preceded the shock), so CR to dark compartment is fear.
For the first few trials, dogs escaped the shock only after it had begun. By the fifth trial the dogs avoided the shock by jumping over the barrier while the light was still turned off before shock commenced. Dogs gradually learnt to avoid the shock all together. Even when shock turned off they kept jumping.
The Avoidance Paradox
After avoidance response was learnt, dogs never received the shock again.
How can the non-occurrence of an event (shock) be a reinforcer?
In discriminated avoidance the warning stimulus becomes aversive by continuity and correlation therefore response that stops the discriminative stimulus, also cancels the impending aversive stimulus > escape contingency: the contingent consequence of the response is the termination of the CS
Two factor theory answer: it is actually removal of the signal that maintains the behaviour
Two Factor Theory
Factor 1: Pavlovian Conditioning.
Factor 2: Operant Conditioning.
Research shows that…
Avoiding the aversive stimulus is... Because of the... Avoidance response (dog jumping over the barrier before shock) is negatively reinforced by... Solves the paradox because it is the removal of a stimulus associated...
NS (light off) + US (mild shock) > UR (fear)
+ US (mild shock) > UR (fear)
+ CS (light off) > CR (fear)
Jumping escapes darkness
light off : jump > escape darkness
adding a feared CS can produce more and faster avoidance responses.
reinforced
reduction of fear when the CS is terminated or removed.
the reduction in fear that accompanies the CS (darkness)
with fear that acts as a negative reinforcer, not the absence of shock.
To falsify two-factor theory
Find evidence of avoidance responses…
when aversive stimuli are not signalled.
Two types of avoidance 1. Discriminated avoidance The aversive event is... 2. Non-discriminated avoidance The aversive event is...
preceded by a stimulus
e.g., asthma inhaler when feeling out of breath
not preceded by a stimulus (2 factor theory doesn’t seem to explain this)
e.g., taking allergy tablets everyday
Sidman’s (1953) Avoidance Task
No responses = shock is delivered every 5 seconds.
Each response rat makes postpones next shock for 30 seconds.
Result:
Rats responded to avoid most shocks.
Apparent problem for two factor theory because no external stimulus
(Q) BUT could the passage of time could act as a signal?
The rats didn’t avoid ALL the shocks, but did manage to avoid most of them. Findings seem consistent with one-factor theory because there is no signal before the shock, yet the avoidance response still occurs. BUT…although there was no external stimulus, the passage of time act as a CS.
(A) Herrnstein & Hineline (1966)
- “random-shock” procedure with no external warning signal.
- Subjects shocked randomly on different shock schedules: HPS (0.3), LPS (0.1).
- Started on HPS. Lever press would switch it to LPS.
- Once shock received on the LPS, switched back to HPS.
- Responding reduced the overall rate of shock but did not guarantee any specific duration of shock-free time.
Result: ?
17 out of 18 rats developed stable avoidance responding with no external CS and where the passage of time could not be a signal.
Responding was reinforced by the reduction in the overall shock rate, not due to any reduction of fear through the removal of a CS = One Factor Theory of Avoidance
The Avoidance Paradox
How can the non-occurrence of an event (shock) be a reinforcer?
Two factor theory answer:
One factor theory answer:
it is actually removal of the signal that maintains the behaviour
decrease in average shock rate maintains responding
Molecular/local explanations focus on….
e.g. two-factor theory
Molar/global explanations focus on….
e.g. one-factor theory.
moment-to- moment relationships between behaviour and consequences
large-scale factors e.g. the overall reduction in shock frequency
“Aversive control” =
The avoidance paradox
The two factors in two factor theory are…
The one factor in one-factor theory is a…
positive punishment and negative reinforcement
a conditioned aversive stimulus (pavlovian) and an escape response (operant)
reduction in the rate of punishers
