Animal Learning Operant Conditioning

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Animal Learning- Operant Conditioning

• Keith Clements

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Aims

• To consider the nature of reinforcement in
  operant conditioning and how differing
  reinforcement schedules alter responding.
• To examine the extent to which biological
  constraints may influence the course of operant
  conditioning.

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Applying Operant conditioning

• Operant conditioning can produce novel behaviours
  through shaping.
• Shaping involves gradually rewarding closer
  approximations to the desired behaviour.
• Any stimulus which increases the frequency of
  behaviour is a reinforcer.
• As well as primary reinforcers, secondary or
  conditioned reinforcers can be used to reward
  behaviour.

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Partial reinforcement reinforcement schedules.

• Ratio schedules provide reinforcement after a
  number of responses. Interval schedules impose a
  delay after each reinforcer, during which no
  further reinforcement is available. Each may be
  fixed or variable
• e.g.
• FR 10 every tenth response is rewarded
• VR 8 an average of 8 responses are needed for
  each reward
• FI 60-sec after a reward is delivered no further
  rewards can be earned until a minute has passed
• VI 30-sec after a successful response no further
  reward is available until around 30 seconds have
  passed

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Responding under partial reinforcement schedules
Variable schedules, in particular, produce
greater resistance to extinction than continuous
reinforcement
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The nature of reinforcement

• Drive reduction theories. Hull (1943)
  reinforcement results from the reduction of the
  drive associated with a physiological need
• The 'Premack principle'. Premacks probability
  differential theory (1965) views reinforcement as
  creating a contingency between two behaviours.
  High probability behaviours can reinforce low
  frequency ones

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Ad Lib
With Contingency in place
Eating Lever pressing
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After training
Eating Lever pressing
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Contingency shaped behaviour Operant principles
apply to learning through direct experience of
the consequences of behaviour. Sometimes,
particularly in human studies, behaviour departs
from the typical patterns. Often humans perform
very badly by comparison with rats or
pigeons! Skinner (1969) argued that this was
because people are capable of Rule-governed
behaviour We can also acquire verbal rules about
the consequences of behaviour without directly
experiencing those consequences. Such behaviour
is often insensitive to it's consequences. Human
behaviour may also differ from that of other
species because of the prior histories of
reinforcement people bring with them.
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What do animals learn during operant conditioning?

• Latent learning (Tolman Honzik, 1930)
• Learning need not involve an immediate change in
  behaviour
• Tolman argued maze learning involves the
  formation of cognitive maps.
• He viewed behaviour as goal-directed, whereas
  early behaviourists such as Hull or Thorndike
  viewed behaviour as automatically elicited by
  environmental stimuli.

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Reinforcer Devaluation

• e.g. Colwill Rescorla (1985)
• Pressing a lever allowed rats to obtain food
  pellets
• Pulling a chain gave access to sugar water.
• One group was given free access to food pellets
  then made ill
• When both the lever and chain were present
  (without reinforcement) this group made few lever
  presses but continued to pull the chain.
• Illness after drinking sugar water had the
  opposite effect.
• Operant responses are produced because they are
  associated with their consequence

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Biological constraints

• Breland Breland's (1961) "misbehaviour of
  organisms". They identified Instinctive drift,
  whereby species-specific behaviours would intrude
  during operant responding.
• Autoshaping (first demonstrated by Brown
  Jenkins, 1968) provides one example of a
  situation where such behaviours may facilitate
  operant conditioning. Pigeons will peck at
  stimuli associated with the presentation of food
  and drink, even when pecking has no effect on the
  delivery of reinforcers.
• E.g. see http//go.owu.edu/deswartz/procedures/au
  toshaping.html

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References

• Last weeks references cover operant conditioning.
• The Classics in the History of Psychology web
  site http//psychclassics.asu.edu includes the
  paper by Breland and Breland, describing their
  experiences, and one by Tolman, setting out his
  alternative to the version of behaviourism which
  dominated the study of learning at the time.

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