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"Behavioral
Psychology"
The
Birth of Behavioral Psychology
Around
the turn of the century, Edward Thorndike attempted to develop
an objective experimental method for testing the mechanical
problem solving ability of cats and dogs. Thorndike devised
a number of wooden crates which required various combinations
of latches, levers, strings, and treadles to open them.
A dog or a cat would be put in one of these puzzle boxes
and, sooner or later, would manage to escape.
Thorndike's initial aim was to show that the anecdotal achievement
of cats and dogs could be replicated in controlled, standardized
circumstances. However, he soon realized that he could now
measure animal intelligence using this equipment. His method
was to set an animal the same task repeatedly, each time
measuring the time it took to solve it. Thorndike could
then compare these learning curves across different situations
and species.
Thorndike was particularly interested in discovering whether
his animals could learn their tasks through imitation or
observation. He compared the learning curves of cats who
had been given the opportunity to observe other cats escape
from a box, with those who had never seen the puzzle being
solved, and found no difference in their rate of learning.
He obtained the same null result with dogs and, even when
he showed the animals the methods of opening a box by placing
their paws on the appropriate levers and so on, he found
no improvement. He fell back on a much simpler, "trial-and-error"
explanation of learning. Occasionally, quite by chance,
an animal performs an action that frees it from the box.
When the animal finds itself in the same position again,
it is more likely to perform the same action again. The
reward of being freed from the box somehow strengthens an
association between a stimulus (being in a certain position
in the box) and an appropriate action. Rewards act to strengthen
these stimulus-response associations. The animal learned
to solve the puzzle-box not by reflecting on possible actions
and really puzzling its way out of it but by a mechanical
development of actions originally made by chance. Thus,
Thorndike demonstrates that the mind of a dog or cat is
not capable of learning by observation but can only learn
what has been personally experienced and reinforced.
By 1910 Thorndike had formalized this notion into the "Law
of Effect," which essentially states that responses that
are accompanied or followed by satisfaction (i.e., a reward,
or what was later to be termed a reinforcement) will be
more likely to reoccur, and those which are accompanied
by discomfort (i.e., a punishment) will be less likely to
reoccur. Thorndike extrapolated his finding to humans and
subsequently maintained that, in combination with the Law
of Exercise (which states that associations are strengthened
by use and weakened by disuse) and the concept of instinct,
the Law of Effect could explain all of human behavior in
terms of the development of a myriad of stimulus-response
associations.
Thorndike,
his laws, and trial-and-error learning became the foundation
for behavioral psychology, and the behaviorist position
that human behavior could be explained entirely in terms
of stimulus-response associations and the effects of reinforcers
upon them. In its purest sense this new field of behavioral
psychology entirely excluded cognitive concepts such as
desires or goals.
John Broadhus Watson in his 1914 book, Behavior: An Introduction
to Comparative Psychology, made the next major step
in the development of behavioral psychology. Watson's theoretical
position was even more extreme than Thorndike's. His rejection
of cognition, or "mentalism," was total and he had no place
for concepts such as pleasure or distress in his explanations
of behavior. He essentially rejected the Law of Effect,
denying that pleasure or discomfort caused stimulus-response
associations to be learned. For Watson, all that was important
was the frequency of occurrence of stimulus-response pairings.
Reinforcers might cause some responses to occur more often
in the presence of particular stimuli, but they did not
act directly to cause their learning. In 1919 Watson published
his second book, Psychology from the Standpoint of a
Behaviorist, which established him as the founder of
the American school of behaviorism.
In the 1920s behaviorism began to wane in popularity. A
number of studies, particularly those with primates (which
are capable of observational, monkey-see, monkey-do, learning),
appeared to show flaws in the Law of Effect and to require
mental representations in their explanation. But in 1938
Burrhus Friederich Skinner powerfully defended and advanced
behaviorism when he published The Behavior of Organisms,
which was arguably the most influential work on animal behavior
of the century. B.F. Skinner resurrected the Law of Effect
in more starkly behavioral terms and developed the Skinner
Box, a technology that allowed sequences of behavior produced
over a long time to be studied objectively, which was a
great improvement on the individual learning trials of Watson
and Thorndike.
Skinner developed the basic concept of "operant conditioning"
which claimed that this type of learning was not the result
of stimulus-response learning. For Skinner, the basic association
in operant conditioning was between the operant response
and the reinforcer, with a discriminative stimulus serving
to signal when the association would be acted upon.
It
is worth briefly comparing trial-and-error learning with
classical conditioning. In in 1890s, Pavlov, a Russian physiologist,
was observing the production of saliva by dogs as they were
fed. He noticed that saliva was also produced when the person
who fed them appeared, even though he was without food.
This is not surprising. Every farm boy for thousands of
years has realized that animals become excited when they
hear the sounds that indicate they are about to be fed.
But Pavlov carefully observed and measured one small part
of the process. He paired a sound, a tone, with feeding
his dogs so that the tone occurred several times right before
and during the feeding. Soon the dogs salivated to the tone,
as they did to the food. They had learned a new connection:
tone with food or tone with saliva response.
In classical conditioning, a neutral stimulus becomes associated
with an involuntary response, such as salivation or increased
heart rate. But operant conditioning involves voluntary
actions (such as lifting a latch, following a maze, or aiming
and firing a weapon) with reinforcing or punishing events
serving to alter the strength of association between the
stimulus and the response.
The ability of behavioral psychology to turn voluntary motor
responses into a conditioned response is demonstrated in
one of Watson's early experiments which studied maze-learning,
using rats in a type of maze that was simply a long, straight
alley with food at the end. Watson found that once the animal
was well trained at running this maze it did so almost automatically,
or reflexively. Once started by the stimulus of the maze
its behavior becomes a series of voluntary motor responses
largely detached from stimuli in the outside world. This
was made clear when Watson shortened the alleyway, which
caused well trained (i.e., conditioned) rats to run straight
into the end of the wall. This was known as the Kerplunk
Experiment, and it demonstrates the degree to which a set
of behaviorally conditioned, voluntary motor responses can
become reflexive, or automatic in nature. Only a few decades
after Watson ran these early, simple experiments, the world
would see the tenets of behaviorism used to instill the
voluntary motor responses necessary to turn close combat
killing into a reflexive and automatic response.
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