Journal
of
Experimental Psychology
VOL. XVIII,
No. 6
DECEMBER,
1935
STUDIES
OF
INTERFERENCE
IN
SERIAL
VERBAL REACTIONS
BY
J.
RIDLEY STROOP»
George
Peabody
College
INTRODUCTION
Interference
or
inhibition
(the
terms seem
to
have been
used almost indiscriminately)
has
been given
a
large place
in
experimental literature.
The
investigation
was
begun
by
the physiologists prior
to 1890
(Bowditch
and
Warren,
J. W.,
1890)
and has
been continued
to the
present, principally
by
psychologists (Lester, 1932).
Of the
numerous studies that
have been published during this period only
a
limited number
of
the
most relevant reports demand
our
attention here.
Miinsterberg (1892) studied
the
inhibiting effects
of
changes
in
common daily habits such
as
opening
the
door
of
his
room, dipping
his pen in ink, and
taking
his
watch
out
of
his
pocket.
He
concluded that
a
given association
can
function automatically even though some effect
of a
previous
contrary association remains.
Mviller
and
Schumann (1894) discovered that more time
*
The writer
wishes
to
acknowledge
the
kind assistance received
in
the preparation
of this thesis.
He is
indebted
to Dr.
Joseph Peterson
for
encouragement, helpful
suggestions,
and
criticism
of the
manuscript;
to
Major
H. W.
Fenker,
a
graduate
student
in
psychology,
for
helpful suggestions relative
to
preparation
of the
manu-
script;
to
Drs.
J.
Peterson,
S. C.
Garrison,
M. R.
Schneck,
J. E.
Caster, O. A. Simley,
W.
F. Smith,
and
to
Miss
M. Nichol
for
aid
in
securing subjects; to
some
three hundred
college students
who
served
as
subjects;
and to
William Fitzgerald
of The
Peabody
Press
for
substantial assistance
in the
printing
of
the test materials.
643
644 /• RIDLEY STROOP
was necessary to relearn a series of nonsense syllables if the
stimulus syllables had been associated with other syllables in
the meantime. From their results they deduced the law of
associative inhibition which is quoted by Kline
(1921,
p. 270)
as follows: "If a is already connected with b, then it is diffi-
cult to connect it with k, b gets in the way." Nonsense syl-
lables were also used by Shepard and Fogelsonger (1913) in
a series of experiments in association and inhibition. Only
three subjects were used in any experiment and the changes
introduced to produce the inhibition were so great in many
cases as to present novel situations. This latter fact was
shown by the introspections. The results showed an in-
crease in time for the response which corresponded roughly
to the increase in the complexity of the situation. The only
conclusion was stated thus: "We have found then that in
acquiring associations there is involved an inhibitory process
which is not a mere result of divided paths but has some deeper
basis yet unknown" (p. 311).
Kline (1921) used 'meaningful' material (states and
capitals, counties and county seats, and books and authors)
in a study of interference effects of associations. He found
that if the first associative bond had a recall power of 10 per-
cent or less it facilitated the second association, if it had a
recall power of 15 percent to 40 percent the inhibitory power
was small, if it had a recall power of 45 percent to 70 percent
the inhibiting strength approached a maximum, if the recall
power was 70 percent to 100 percent the inhibition was of
medium strength and in some cases might disappear or even
facilitate the learning of a new association.
In card sorting Bergstrom (1893 and 1894), Brown (1914),
Bair (1902), and Culler (1912) found that changing the
arrangement of compartments into which cards were being
sorted produced interference effects. Bergstrom (1894, p.
441) concluded that "the interference effect of an association
bears a constant relation to the practice effect, and is, in fact,
equivalent to it." Both Bair and Culler found that the inter-
ference of the opposing habits disappeared if the habits were
practiced alternately.
INTERFERENCE JN SERIAL VERBAL
REACTIONS-
645
Culler (1912), in the paper already referred to, reported
two other experiments. In one experiment the subjects
associated each of a series of numbers with striking a parti-
cular key on the typewriter with a particular finger; then the
keys were changed so that four of the numbers had to be
written with fingers other than those formerly used to write
them. In the other experiment the subjects were trained to
react with the right hand to 'red' and with the left hand to
'blue.'
Then the stimuli were interchanged. In the former
experiment an interference was found which decreased rapidly
with practice. In the latter experiment the interference was
overbalanced by the practice effect.
Hunter and Yarbrough (1917), Pearce (1917), and Hunter
(1922) in three closely related studies of habit interference
in the white rat in a T-shaped discrimination box found that
a previous habit interfered with the formation of an 'opposite'
habit.
Several studies have been published which were not pri-
marily studies of interference, but which employed materials
that were similar in nature to those employed in this research,
and which are concerned with why it takes more time to
name colors than to read color names. Several of these
studies have been reviewed recently by Telford (1930) and
by Ligon (1932). Only the vital point of these studies will
be mentioned here.
The difference in time for naming colors and reading color
names has been variously explained. Cattell (1886) and
Lund (1927) have attributed the difference to 'practice.'
Woodworth and Wells
(1911,
p. 52) have suggested that,
"The real mechanism here may very well be the mutual
interference of the five names, all of which, from immediately
preceding use, are 'on the tip of the tongue,' all are equally
ready and likely to get in one another's way." Brown (1915,
p.
51) concluded "that the difference in speed between color
naming and word reading does not depend upon practice"
but that (p. 34) "the association process in naming simple
objects like colors is radically different from the association
process in reading printed words."
646 /. RIDLEY STROOP ]
Garrett and Lemmon (1924, p. 438) have accounted for
their findings in these words, "Hence it seems reasonable to
say that interferences which arise in naming colors are due
not so much to an equal readiness of the color names as to an
equal readiness of the color recognitive processes. Another
factor present in interference is very probably the present
strength of the associations between colors and their names,
already determined by past use." Peterson (1918 and 1925)
has attributed the difference to the fact that, "One particular
response habit has become associated with each word while
in the case of colors themselves a variety of response ten-
dencies have developed." (1925, p. 281.) As pointed out by
Telford (1930), the results published by Peterson (1925,
p.
281) and also those published by Lund (1927, p. 425)
confirm Peterson's interpretation.
Ligon (1932) has published results of a 'genetic study'
of naming colors and reading color names in which he used
638 subjects from school grades 1 to 9 inclusive. In the
light of his results he found all former explanations untenable
(He included no examination of or reference to Peterson's
data and interpretation.) and proceeded to set up a new
hypothesis based upon a three factor theory, a common factor
which he never definitely describes and special factors of
word reading and color naming. He points out that the com-
mon factor is learned but the special factors are organic. He
promises further evidence from studies now in progress.
The present problem grew out of experimental work in
color naming and word reading conducted in Jesup Psy-
chological Laboratory at George Peabody College For
Teachers. The time for reading names of colors had been
compared with the time for naming colors themselves. This
suggested a comparison of the interfering effect of color
stimuli upon reading names of colors (the two types of
stimuli being presented simultaneously) with the interfering
effect of word stimuli upon naming colors themselves. In
other words, if the word 'red' is printed in blue ink how will
the interference of the ink-color 'blue' upon reading the
printed word 'red' compare with the interference of the
INTERFERENCE
IN
SERIAL VERBAL REACTIONS
647
printed word
'red'
upon calling
the
name
of the
ink-color
'blue?'
The
increase
in
time
for
reacting
to
words caused
by
the
presence
of
conflicting color stimuli
is
taken
as the
measure
of the
interference
of
color stimuli upon reading
words.
The
increase
in the
time
for
reacting
to
colors
caused
by the
presence
of
conflicting word stimuli
is
taken
as
the measure
of the
interference
of
word stimuli upon naming
colors.
A
second problem grew
out of the
results
of the
first.
The problem
was,
What effect would practice
in
reacting
to
the color stimuli
in the
presence
of
conflicting word stimuli
have upon
the
reaction times
in the two
situations described
in
the
first problem?
EXPERIMENTAL
The materials employed
in
these experiments
are
quite
different from
any
that have been used
to
study interference.
1
In former studies
the
subjects were given practice
in
respond-
ing
to a set of
stimuli until associative bonds were formed
between
the
stimuli
and the
desired responses, then
a
change
was made
in the
experimental
'set up'
which demanded
a
different
set of
responses
to the
same
set of
stimuli.
In the
present study pairs
of
conflicting stimuli, both being inherent
aspects
of the
same symbols,
are
presented simultaneously
(a
name
of one
color printed
in the ink of
another color—a
word stimulus
and a
color stimulus). These stimuli
are
varied
in
such
a
manner
as to
maintain
the
potency
of
their
interference effect. Detailed descriptions
of the
materials
used
in
each
of the
three experiments
are
included
in the re-
ports
of the
respective experiments.
EXPERIMENT
I
The Effect
of
Interfering Color Stimuli Upon Reading Names
of Colors Serially
Materials:
When this experiment
was
contemplated,
the
first task
was to
arrange suitable
tests.
The
colors used
on the
Woodworth-Wells color-sheet were considered
but two
changes were deemed advisable.
As the
word test
to be
used
in
comparison with
the
1
Descoeudres (1914)
and
also Goodenough
and
Brian (1929) presented color
and
form simultaneously
in
studying their relative values
as
stimuli.