Extinction
Extinction results when the learnt response occurs but is no longer
followed by reinforcement or when one always presents a conditioned
stimulus without the unconditioned stimulus. The effect of these
procedures is an eventual reduction in response strength, as
measured for example, in rate of response. Humans rarely work with
reliable enthusiasm if they are not paid. The same can be seen in
non-human animals. If they don’t get their expected rewards they are
less likely to behave in ways that have previously paid off. The
behaviours drop out or become extinct. Extinction occurs when an
animal no longer receives a reward for a correct response and
eventually stops responding. Dogs that beg at dinner tables stop
begging if they are never rewarded. Often extinction is accompanied
by reversion to innate behaviours instead of simply an absence of
the learned responses. Occasionally animals may experiment at this
point by adopting sequences of other learned behaviours in an
attempt to acquire rewards. If, during the extinction process, a
novel stimulus is presented just before the conditioned stimulus,
unlearning is accelerated. This technique is called disinhibition.
There are some intriguing outcomes associated with extinction. Early
in extinction it is usual for a "frustration effect" to occur, so
called because one theory proposes the subject responds faster
because it is "frustrated". To avoid misinterpreting an extinction-based behaviour modification program as a failure, it is important
for therapists to be aware that the frustration effect occurs.
Things will usually get transiently worse before they get better.
For example, rather like a human repeatedly pressing the on switch
of a faulty television set, a horse that has learned to break the
rope that tethers it by being been reinforced with liberty will pull
much harder when first it is tethered by a chain.
Because extinction does not occur in a vacuum, stimuli present
during extinction can exert considerable control over behaviour.
Therefore a dog that begs at the dinner table and scavenges food
from semi-feral toddlers will extinguish this response if it
receives no further rewards. If the presence of a grandmother at the
family table, laying down the rules about table manners and less
than messy eating, is associated with the absence of reinforcement
then the extinction will occur most quickly when Granny is at home.
Extinction can apply to any behaviour that occurs and is no longer
reinforced. Both welcome and unwelcome behavioural responses will
weaken in the absence of reinforcement. If after a long rest
interval between trials, further conditional stimuli (cues) are
presented, they elicit a conditional response that is much higher
than in the previous of the extinction trials. This rebound in
response strength after a 'rest', following extinction, is called
spontaneous recovery. It is often overlooked in behaviour therapy
designed to eliminate unwelcome behaviours by extinction. If an
undesirable behaviour makes a return, trainers often forget the
original response strength when they compare current behaviour with
previous behaviour. So, when the response recurs after a long
absence, the trainer's conclusion is slightly damning with remarks
like "the removal of rewards hasn’t helped" or "the animal has
regressed". In fact, like the hearty glow of a candle flame before
it dies out, this is the typical pattern found in extinction. This
is particularly important with habituated responses that can show
spontaneous recovery if reinforcement is withheld. To prevent the
original fearful response reoccurring, the trainer must continue to
expose the animal to the relevant stimuli from time to time.
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