Psy 551
Handout on Thorndike's Law of Effect

STATEMENT OF 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 recur.  The greater the satisfaction or discomfort, the
greater the strengthening or weakening of the bond.  (Thorndike,
1911, p. 244)

THREE PARTS:

1.  Satisfiers strengthen
2.  Annoyers weaken
3.  Degree of strengthening or weakening is proportional to degree
of satisfaction or discomfort

Thorndike abandoned the negative half (#2) by 1930.

REJOINDER TO CHARGE THAT IT IS CIRCULAR:

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 or abandons.  (Thorndike, 1911, p.
245)

This rejoinder anticipated a principle called "transsituationality" that
would be proposed some years later.

PREDECESSORS

Classical Hedonism

Spencer-Bain principle (originated between 1855-1870 and
remained influential until 1911): "On the recurrence of the
circumstances, these muscular movements that were followed by
success are likely to be repeated; what was at first an accidental
combination of motions will now be a combination having
considerable probability."