Download Thorndike and the Law of Effect

Thorndike and the Law of
Effect
Experimental research on instrumental
conditioning begins with Thorndike’s
classic “puzzle box” experiments.
George Romanes (1848-1894)
n
Influenced by Darwin’s theory of
evolution:
q
q
n
Evolution toward intelligent, problemsolving abilities may have begun early
Consequently, such abilities should be
apparent in animals other than us
humans
Wrote Animal Intelligence (1882)
q
Used anecdotal evidence to support
the view that animals are capable of
reasoning and problem -solving, such
as dogs or cats learning to operate a
door-latch to let themselves out.
Edward L. Thorndike’s Criticism of
Romanes’ Animal Intelligence
n
n
Anecdotal evidence not
reliable
Nobody had actually
observed the animals
learning to operate a
latch mechanism –
Romanes simply
assumed that it had
taken reasoning to
solve the problem.
1
Thorndike’s Alternative: Experiment
n
n
n
Only an experiment can show how animals
actually go about solving problems such as
the operation of a door-latch.
Consequently, he built several “puzzle
boxes,” made from old fruit crates, equipping
each with different types of latch-mechanism.
Dogs or cats would be placed inside the box
and observed as they went about learning
how to operate the latch.
One of Thorndike’s Puzzle Boxes
Although crudely
made, boxes like
this one served
their purpose.
Note the door at
front center,
complete with a
latch that can be
operated from
inside.
Box A
Experimental Procedure
n
n
n
n
n
n
Place a bit of fish in a bowl outside of the
puzzlebox.
Place a cat inside the box and latch the door
behind it.
Start your stopwatch.
Observe what the cat does.
When the cat emerges from the box, stop the
stopwatch, record the data, and let the cat eat a
bit of the fish.
Repeat for trial 2, 3, and so on, until the cat is
rapidly escaping from the box.
2
Example Puzzle-box Data
This shows results
for four cats in the
same box previously
pictured.
The gaps labeled
with number days
represent tests of
retention.
The Law of Effect
“Of several responses made to the same situation,
those which are accompanied or closely followed by
satisfaction to the animal will, other things being
equal, be more firmly connected with the situation, so
that, when it recurs, they will be more likely to recur;
those which are accompanied or closely followed by
discomfort to the animal will, other things being
equal, have their connections with that situation
weakened, so that, when it recurs, they will be less
likely to occur. The greater the satisfaction or
discomfort, the greater the strengthening or
weakening of the bond. “
Thorndike (1914)
Analysis of the Law of Effect
n
n
n
n
A “situation” is all those stimuli, both external and
internal, that identify a given circumstance (in
Thorndike’s experiment, being hungry and confined
in a puzzle box).
The situation elicits a variety of behaviors by virtue
of associative connections between stimulus and
response (some innate, some learned).
When a given response is accompanied or followed
by “satisfaction,” its S-R connection to the situation
is strengthened, thus increasing the probability of
that behavior in that situation (positive law of effect).
Discomfort has the opposite effect, weakening the
S-R bond and thus decreasing the probability of the
behavior (negative law of effect).
3
The Law of Effect as Darwinian Selection
n
n
n
Variation – A given “situation” elicits a certain
population of behavioral acts, some of which
occur with higher or lower probability than
others.
Selection – Satisfiers and discomforters play
the role of selection, determining which
behaviors will be favored or disfavored.
Like Begets Like – Those behavioral acts
selected occur more often in the population in
succeeding trials (differential survival).
Criticism of Thorndike’s Law of Effect
n
n
Critics chastised Thorndike for using
mentalistic terms like “satisfaction” and
“discomfort.” How could Thorndike know
what was going on in the animal’s mind?
However, Thorndike was ahead of his critics,
as he had been careful to provide operational
definitions in terms of objective behavior, as
shown on the next slide.
Thorndike on Satisfaction and Discomfort
By a satisfying state of affairs is meant one which the animal
does nothing to avoid, often doing such things as attain and
preserve it. By a discomforting or annoying state of affairs is
meant one which the animal commonly avoids and abandons.
The satisfying and annoying are not synonymous with
favorable and unfavorable to the life of either the individual or
the species. Many animals are satisfied by deleterious
conditions. Excitement, overeating, and alcoholic intoxication
are, for instance, three very common and very potent satisfiers
of man. Conditions useful to the life of the species in
moderation are often satisfying far beyond their useful point:
many conditions of great utility to the life of the species do n ot
satisfy and may even annoy its members.
Thorndike (1914)
4