Gender
Age
1
18
1
18
1
18
1
18
1
18
1
19
1
19
1
19
1
20
1
20
1
20
1
21
1
21
1
22
1
22
1
22
1
22
1
22
1
22
1
22
1
22
1
22
1
22
1
23
1
23
1
23
1
23
1
23
1
23
1
23
1
24
Read Word (timeSay
in seconds)
Color (timeThe
in seconds)
Stroop Effect – the difference between Say Color and Read Word (seconds)
75.1
80.9
5.8
73.8
76.9
3.1
74.1
77.3
3.2
76
79.1
3.1
79.1
81.2
2.1
73.6
76.8
3.2
74.8
78.6
3.8
79.6
81.6
2
76.6
79.1
2.5
77.1
79.9
2.8
80.2
82
1.8
73.5
76.7
3.2
77.5
80.7
3.2
74.8
78.6
3.8
75.1
78.9
3.8
75.3
79
3.7
76.5
79.1
2.6
77.8
80.8
3
78.5
81.1
2.6
79.6
81.9
2.3
80
82
2
80.3
82.1
1.8
80.4
82.3
1.9
74.1
77.4
3.3
74.1
77.6
3.5
74.5
78.2
3.7
74.6
78.5
3.9
76.6
79.1
2.5
79.9
81.9
2
80
82
2
74.3
78.1
3.8
1
24
1
24
1
25
1
25
1
25
1
25
1
25
1
60
1
60
1
60
1
60
1
61
1
61
1
61
1
61
1
61
1
61
1
62
1
63
1
63
1
63
1
63
1
65
1
65
1
65
1
65
1
66
1
66
1
66
1
66
1
67
1
68
75
79.3
76.8
77
77.3
78.2
78.4
82.3
78.3
83.7
80.1
80.9
81
82.2
81.4
81.5
82.8
84
82.1
78.5
78
81.7
82.9
81.1
79.3
80.9
80.2
81.1
80.9
82.1
79.1
82.7
78.7
81.3
79.4
79.6
80.6
81
81.1
85.3
84.4
85.5
86.7
86
84.6
84.2
85.2
86.5
86.1
84.3
85.3
87.9
83.8
87.6
83.2
88.5
87.1
85
87
86.9
88.4
87
83.9
87.5
3.7
2
2.6
2.6
3.3
2.8
2.7
3
6.1
1.8
6.6
5.1
3.6
2
3.8
5
3.3
0.3
3.2
9.4
5.8
5.9
0.3
7.4
7.8
4.1
6.8
5.8
7.5
4.9
4.8
4.8
1
68
1
69
1
69
1
69
1
70
1
70
1
70
1
70
1
71
1
71
1
72
1
72
1
72
1
72
1
73
1
74
1
75
1
75
2
18
2
18
2
19
2
19
2
19
2
19
2
19
2
19
2
19
2
19
2
19
2
19
2
20
2
20
84.2
84
78.5
78.5
78.9
78.4
78.3
83.6
81.5
81.6
83.8
83.5
80
81
84
80.4
83.4
78.8
74.7
74.7
70.1
70.2
70.6
70.7
72
72.6
73.3
73.7
73.9
74.4
70.8
71
86.9
86.6
85
84.2
86.4
85.4
85.2
85.2
84.2
88.8
86.1
83.6
84.2
87.3
86.5
88.8
83.8
86
75
79.9
74
74
74.3
74.5
74.9
75.3
76.3
77.3
77.4
79.2
74.8
74.8
2.7
2.6
6.5
5.7
7.5
7
6.9
1.6
2.7
7.2
2.3
0.1
4.2
6.3
2.5
8.4
0.4
7.2
0.3
5.2
3.9
3.8
3.7
3.8
2.9
2.7
3
3.6
3.5
4.8
4
3.8
2
20
2
21
2
21
2
21
2
22
2
22
2
22
2
22
2
22
2
23
2
23
2
23
2
23
2
24
2
24
2
24
2
24
2
24
2
24
2
25
2
25
2
25
2
25
72.4
70
71.1
74
72.2
73.3
73.4
74.1
74.6
69.6
72.4
72.7
73.2
70.5
72.7
72.8
73.1
73.6
74.1
69.7
70
71.6
74
2
60
74.3
2
60
73.2
2
60
74.5
2
60
75
2
62
73.9
2

62
75.2
2
62
75.5
2
63
71.9
2
63
73.2
75
73.8
74.9
77.7
75
76.4
77
78.6
79.8
73.6
75.1
75.6
76
74.2
75.7
75.9
76
77
78.9
73.8
73.9
74.9
78
77.4
80.6
82.5
83.5
82.3
83.5
83.8
78
80.7
2.6
3.8
3.8
3.7
2.8
3.1
3.6
4.5
5.2
4
2.7
2.9
2.8
3.7
3
3.1
2.9
3.4
4.8
4.1
3.9
3.3
4
3.1
7.4
8
8.5
8.4
8.3
8.3
6.1
7.5
Averages
2
63
74.9
2
64
71.8
2
64
72.8
2
64
73.5
2
64
75.3
2
65
72.5
2
65
74.1
2
66
71.1
2
67
70.6
2
67
73.2
2
68
75.5
2
69
72.4
2
69
75.9
2
71
72.3
2
71
72.9
2
71
75.3
2
72
74
2
73
72.4
2
73
72.7
2
74
71.1
2
74
72.2
2
74
75.3
2
75
73.4
44.12
76.26866667
82.8
78
80.1
81.8
83.5
79.1
82.5
77.1
76.3
80.8
83.9
78.8
81
78.4
80.3
83.6
82.4
78.9
80
77.8
78.4
83.7
81.1
80.762
7.9
6.2
7.3
8.3
8.2
6.6
8.4
6
5.7
7.6
8.4
6.4
5.1
6.1
7.4
8.3
8.4
6.5
7.3
6.7
6.2
8.4
7.7
4.493333333
2/15/22, 8:36 PM
Criteria
Introduction
and
Literature
Review
Methods
Results
https://learn.umgc.edu/content/enforced/623405-006726-01-2222-OL1-6381/Paper Grading Rubric.html
Level 5
20 points
Level 15-19
19 points
Level 10-14
14 points
Level 1-9
9 points
Level
0
0
points
at least 8 appropriate
references are used to
describe the relevant
background information
clearly stated hypothesis
generally well written with
appropriate grammar,
tense, and sentence
structure
information presented
clearly and concisely
5-7 references with some
relevant background
information not included
uses one or more reference
that isn’t appropriate
hypothesis not clearly
stated
generally well written with
mostly appropriate grammar
and sentence structure
information presented is
mostly clear
3-4 appropriate references with
a large proportion of relevant
background information not
included
hypothesis unclear or not
included
some use of poor grammar and
sentence structure
information presented is not
entirely clear and/or not concise
1-2 appropriate references and
lacking significant background
information
hypothesis not included
Not
poorly written (grammar and tense
Done
incorrect making it difficult to read,
poor use of sentence structure)
information presented is unclear and
doesn’t flow together
completely describes all
elements (participants,
materials, and
design/procedure including
how data was analyzed)
includes Review Board
Form (RBF) that is
appropriately filled out –
place in appendix- refer to
in methods section
appropriate grammar,
tense, and sentence
structure used
descriptions are clear and
include all appropriate
details
describes all three elements
but one or more
descriptions lacks detail
includes RBF that is
appropriately filled out or
lacking minor details
generally uses appropriate
grammar, tense, and
sentence structure
descriptions are generally
clear and/or concise
descriptions of elements
missing or incomplete, some
poor grammar and use of tense,
unclear descriptions, lack of
appropriate sentence structure
includes RBF but lacks details
or contains incorrect information
lack of description for all three
elements and those included are
incomplete and/or poorly written,
poor use of grammar and tense,
Not
descriptions lack significant details Done
includes RBF but lacks appropriate
information or contains incorrect
information
clearly describes data and
main findings in sufficient
detail
uses tables and figures
effectively to represent
exact values, main effects,
or interactions
states results of
descriptive and inferential
statistics (including
significance levels)
describes data and main
findings in nearly sufficient
detail or lacks clarity
uses tables and figures to
represent exact values,
main effects, or interactions,
but not efficiently
states results of descriptive
and inferential statistics,
without significance levels
https://learn.umgc.edu/content/enforced/623405-006726-01-2222-OL1-6381/Paper Grading Rubric.html
describes data or main findings
without sufficient detail and
clarity
uses tables and figures to
represent unimportant details of
results
states results of descriptive or
inferential statistics
describes data and main findings
without sufficient detail and clarity
no figures or tables
no results from descriptive or
inferential statistics
Not
Done
1/2
2/15/22, 8:36 PM
Discussion
Abstract
and APA
Abstract
APA
Overall
Score
https://learn.umgc.edu/content/enforced/623405-006726-01-2222-OL1-6381/Paper Grading Rubric.html
provides overview of
results
interprets results in light of
literature discussed in the
introduction
restates hypothesis and
includes conclusions
supported by the results
Level 10
10 points
includes all required
components
writing is in APA style
generally well written with
appropriate grammar,
tense, and sentence
structure
information presented
clearly and concisely
no more than 5 APA formatting
errors throughout the entire
paper
Level 5
100 or more
restates results from
previous section
interpret results in light of
some literature discussed in
the introduction
restates hypothesis and
states conclusion
Level 5-9
9 points
includes some components
writing not entirely APA
style
some
grammatical/tense/sentence
structure issues
information presented lacks
clarity
restates results from previous
section
does not interpret results in light
of literature discussed in the
introduction
restates hypothesis without
conclusion
Level 1-4
4 points
https://learn.umgc.edu/content/enforced/623405-006726-01-2222-OL1-6381/Paper Grading Rubric.html
Level 0
0 points
includes some components
APA style writing not used
poor grammar and/or sentence
Not Done
structure
information presented is unclear
and doesn’t flow together
no more than 8 APA formatting
no more than 10 APA formatting
errors throughout the entire paper errors throughout the entire paper
Level 4
70 or more
limited or no discussion of results
Not
limited or no discussion of literature
Done
limited or no hypothesis statement
Level 3
42 or more
more than 10 APA formatting errors
throughout the entire paper
Level 2
4 or more
Level
1
0 or
more
2/2
For this assignment, you will complete a research paper on The Stroop
Effect and selective attention. The Stroop Effect is a phenomenon that
occurs with the Stroop Task, a test that looks at what happens when we
are asked to perform an ordinary task (such as reading or identifying a
list of colors) when there is some sort of visual interference.
You are acting like you are the researcher who conducted this study!
However, you do not have to actually collect the data – I already have
that for you. In order to understand how the study works and how data
was collected, you will need to participate in an online experiment on
the Stroop Effect located within the “psychology learning tools”.
Remember that you did this earlier in the class!
Once you have completed the experiment you will need to analyze
data (remember that I will give you data) and write a lab report (7- 10
pages – this page count does not include the title page or references)
in APA style consisting of the following sections:
•
•
•
•
•
•
•
Title Page
Abstract
Introduction
Method
Results
Discussion
References
(More information on each section is located below)
Here is the data file: DATA (uploaded as excel spreadsheet)
Remember that you were given additional details in the Hypothesis
discussion. (Uploaded as a word document).
You will write the report as if you were the researcher conducting the
experiment. You have some options in your research question for this
project. The data you are given includes the gender and age of the
participants as well as two columns of results data (reading the words
and saying the colors). If you have a particular interest and want to
modify the data, you have that choice. We will talk about this as you
work on your hypothesis. You should try to use as much of your data as
possible. Do not discard data unless there is a really good reason to do
so.
Careful attention must be paid to APA Style as it represents a
significant portion of your grade for the paper and is an intended
learning outcome for the course. At the end of the term, you will
submit your completed paper to your assignment folder.
Here is the grading rubric for the paper: Rubric (uploaded as pdf)
Main components on your research paper
1. Title page – Make sure that the main points of a title page are
included.
2. Abstract – This is a well written summary of your paper. A reader
should be able to get a clear picture of your paper based on the
abstract. Include everything from a quick introduction of the topic
to a sentence that implies that you will discuss results and
implications.
3. Introduction – This is so much more than a summary of your
paper and should not be treated that way. For this paper, your
introduction should be 2-3 pages of double spaced writing. Start
by introducing your topic in general. Then you should discuss
research from relevant published studies. Most, if not all, of your
8 references from peer reviewed sources will be cited in this
section. Discussing these studies are important as they help
provide a rationale for your study. Give that rationale next. Finish
by clearly stating your hypothesis.
a. Here is an article to get you started. Remember that this
website isn’t the source for this article. You need to locate
and cite the original source!
4. Methods – Split this section into participants, materials and
procedures subsections. You know the gender and age of all of
your participants. You are welcome to include other demographic
or recruiting information as it helps you with your study. Try the
study here so you can adequately write about the procedures.
https://www.memozor.com/other-memory-games/wordsmemory-games/stroop-effect-game
5. Results – Use the data I provided to calculate your results.
Remember that your hypothesis drives your statistics. Think about
what statistics you need to include to test your hypothesis. Write
out all of your results even if you are including them in a table.
Don’t forget to include a chart or table!
6. Discussion – This is the best section because it is finally time to
talk about what YOU think. After restating your results, talk about
what they mean. What are the implications of your findings? Why
are they important? For instance, why should we care that one
gender is better at this than the other or that there aren’t gender
differences for this study? After that, talk about the limitations to
your study and give specific ideas for future research.
7. References – Don’t forget that your references (and all of your
paper) need to be in APA format. You need at least 8 references
from peer reviewed sources (e.g., journals).
2/15/22, 8:37 PM
Classics in the History of Psychology — Stroop (1935)
Classics in the History of Psychology
An internet resource developed by
Christopher D. Green
York University, Toronto, Ontario
(Return to Classics index)
STUDIES OF INTERFERENCE IN SERIAL VERBAL REACTIONS
J. Ridley Stroop[1] (1935)
George Peabody College
First published in Journal of Experimental Psychology, 18, 643-662.
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.
Münsterberg (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.
Müller and Schumann (1894) discovered that more time [p. 644] 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 difficult to connect it with k, b gets in the way.”
Nonsense syllables 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 increase 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 percent 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 associaiton.
In card sorting Bergström (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. Bergström (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
interference of the opposing habits disappeared if the habits were practiced alternately.
[p. 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 particular 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 Tshaped discrimination box found that a previous habit interfered with the formation of an ‘opposite’ habit.
Several studies have been published which were not primarily 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 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
psychclassics.yorku.ca/Stroop/
1/10
2/15/22, 8:37 PM
Classics in the History of Psychology — Stroop (1935)
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.”
[p. 646] 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 tendencies have developed.” (1925, p.
281.) As pointed out by Telford (1930), the results published by Peterson (1925, p. 281) and also 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 common 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 Psychological 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 [p. 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.[2] In former studies the
subjects were given practice in responding 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 reports 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
[p. 648] color test was to be printed in black it seemed well to substitute another color for black as an interfering stimulus. Also, because of
the difficulty of printing words in yellow that would approximate the stimulus intensity of the other colors used, yellow was discarded. After
consulting with Dr. Peterson, black and yellow were replaced by brown and purple. Hence, the colors used were red, blue, green, brown, and
purple. The colors were arranged so as to avoid any regularity of occurrence and so that each color would appear twice in each column and in
each row, and that no color would immediately succeed itself in either column or row. The words were also arranged so that the name of each
color would appear twice in each line. No word was printed in the color it named but an equal number of times in each of the other four
colors; i.e. the word ‘red’ was printed in blue, green, brown, and purple inks; the word ‘blue’ was printed in red, green, brown, and purple inks;
the word ‘blue’ was printed in red, green, brown, and purple inks; etc. No word immediately succeeded itself in either column or row. The test
was printed from fourteen point Franklin lower case type. The word arrangement was duplicated in black print from same type. Each test was
also printed in the reverse order which provided a second form. The tests will be known as “Reading color names where the color of the print
and the word are different” (RCNd),[3] and “Reading color names printed in black” (RCNb).
Subjects and Procedure:
Seventy college undergraduates (14 males and 56 females) were used as subjects. Every subject read two whole sheets (the two forms) of
each test at one sitting. One half of the subjects of each sex, selected at random, read the tests in the order RCNb (form 1), RCNd (form 2),
RCNd (form 1) and RCNb (form 2), while the other half reversed the order thus equating for practice and fatigue on each test and form. All
subjects were seated so as to have good daylight illumination from the left side only. All subjects were in the experimental room a few
minutes before beginning work to allow the eyes to adjust to light conditions. The subjects were volunteers and apparently the motivation
was good.
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A ten-word sample was read before the first reading of each test. The instructions were to read as quickly as possible and to leave no errors
uncorrected. When an error was left the subject’s attention was called to that fact as soon as the sheet was finished. On the signal “Ready!
Go!” the sheet which the subject held face down was turned by the subject and read aloud. The words were followed on another sheet (in
black print) by the experimenter and the time was taken with a stop watch to a fifth of a second. Contrary to instructions 14 subjects left a
total of 24 errors uncorrected on the RCNd test, 4 was the maximum for any subject, and 4 other subjects left 1 error each on the RCNb test.
As each subject made 200 reactions on each test this small number of errors was considered negligible. The work was done under good
daylight illumination.
Results: Table 1 gives the means (m), standard deviations (s), differences (D), probable error of the difference (P Ed), and the reliability of
the difference (D / P Ed) for the whole group and for each sex.
Observation of the bottom line on the table shows that it [p. 649] took an average of 2.3 seconds longer to read 100 colors names printed in
colors different from that named by the word than to read the same names printed in black. This difference is not reliable which is in
agreement with Peterson’s prediction made when the test was first proposed.
The means for the sex groups show no particular difference. An examination of the means and standard deviations for the two tests shows
that the interference factor caused a slight increase in the variability for the whole group and for the female group, but a slight decrease for
the male group.
Table II presents the same data arranged on the basis of college classification. Only college years one and two contain a sufficient number of
cases for comparative purposes. They show no differences that approach reliability.
EXPERIMENT 2
The Effect of Interfering Word Stimuli upon Naming Colors Serially
Materials:
For this experiment the colors of the words in the RCNd test, described in Experiment I, were printed in the same order but in the form of
solid squares (n) from 24 point type instead of words. This sort of problem will be referred to as the [p. 650] “Naming color test” (NC). The
RCNd test was employed also but in a very different manner from that in Experiment I. In this experiment the colors of the print of the series
of names were to be called in succession ignoring the colors named by the words; e.g. where the word ‘red’ was printed in blue it was to be
called ‘blue,’ where it was printed in green it was to be called ‘green,’ where the word ‘brown’ was printed in red it was to be called ‘red,’ etc.
Thus color of the print was to be the controlling stimulus and not the name of the color spelled by the word. This is to be known as the
“Naming color or word test where the color of the print and the word are different” (NCWd). (See Appendix B. [sic – A?])
Subjects and Procedure:
One hundred students (88 college undergraduates, 29 males and 59 females, and 12 graduate students, all females) served as subjects. Every
subject read two whole sheets (the two forms) of each test at one sitting. Half of the subjects read in the order NC, NCWd, NCWd, NC, and
the other half in the order NCWd, NC, NC, NCWd, thus equating for practice and fatigue on the two tests. All subjects were seated (in their
individual tests) near the window so as to have good daylight illumination from the left side. Every subject seemed to make a real effort.
A ten-word sample of each test was read before reading the test the first time. The instructions were to name the colors as they appeared in
regular reading line as quickly as possible and to correct all errors. The methods of starting, checking errors, and timing were the same as
those used in Experiment 1. The errors were recorded and for each error not corrected, twice the average time per word for the reading of the
sheet on which the error was made was added to the time taken by the stop watch. This plan of correction was arbitrary but seemed to be
justified by the situation. There were two kinds of failures to be accounted for: first, the failure to see the error: and second, the failure to
correct it. Each phase of the situation gave the subject a time advantage which deserved taking note of. Since no accurate objective measure
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was obtainable and the number of errors was small the arbitrary plan was adopted. Fifty-nine percent of the group left an average of 2.6 errors
uncorrected on the NCWd test (200 reactions) and 32 percent of the group left an average of 1.2 errors uncorrected on the NC test (200
reactions). The correction changed the mean on the NCWd test from 108.7 to 110.3 and the mean of the NC test from 63.0 to 63.3.
Results: The means of the times for the NC and NCWd tests for the whole group and for each sex are presented in Table III along with the
difference, the probable error of the [p. 651] difference, the reliability of the difference, and difference divided by the mean time for the
naming color test.
The comparison of the results for the whole group on the NC and NCWd test given in the bottom line of the table indicates the strength of the
interference of the habit of calling words upon the activity of naming colors. The mean time for 100 responses is increased from 63.3 seconds
to 110.3 seconds or an increase of 74 percent. (The medians on the two tests are 61.9 and 110.4 seconds respectively.) The standard deviation
is increased in approximately the same ratio from 10.8 to 18.8. The coefficient of variability remains the same to the third decimal place ( s /
m = .171). The difference between means may be better evaluated when expressed in terms of the variability of the group. The difference of
47 seconds is 2.5 standard deviation units in terms of the NCWd test or 4.35 standard deviation units on the NC test. The former shows that
99 percent of the group on the NCWd test was above the mean on the NC test (took more time); and the latter shows that the group as scored
on the NC test was well below the mean on the NCWd test. These results are shown graphically in Fig. 1 where histograms and normal curves
(obtained by the Gaussian formula) of the two sets of data are superimposed.
The small area in which the curves overlap and the 74 percent increase in the mean time for naming colors caused by the presence of word
stimuli show the marked interference effect of the habitual response of calling words.
[p. 652] The means for the sex groups on the NCWd test show a difference of 3.6 seconds which is only 1.16 times its probable error; but the
means on the NC test have a difference of 8.2 seconds which is 5.17 times its probable error. This reliable sex-difference favoring the females
in naming colors agrees with the findings of Woodworth-Wells (1911), Brown (1915), Ligon (1932), etc.
The same data are arranged according to college classification in Table IV. There is some indication of improvement of the speed factor for
both tests as the college rank improves. The relative difference between the two tests, however, remains generally the same except for
fluctuations which are probably due to the variation in the number of cases.
EXPERIMENT 3
The Effects of Practice upon Interference
Materials:
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The tests used were the same in character as those described in Experiments 1 and 2 (RCNb, RCNd, NC, and NCWd) with some revision. The
NC test was printed in swastikas ( ) instead of squares (n). Such a modification allowed white to appear in the figure with the color, as is the
case when the color is presented in the printed word. This change also made it possible to print the NC test in shades which more nearly
match those in the NCWd test. The order of colors was determined under one restriction other than those given in section 2. Each line
contained one color whose two appearances were separated by only one other color. This was done to equate, as much as possible, the
difficulty of the different lines of the test so that any section of five lines would approximate the difficulty of any other section of five lines.
Two forms of the tests were printed; in one the order was the inverse of that in the other.
[p. 653] Subjects and Procedure:
Thirty-two undergraduates in the University of Arizona (17 males and 15 females), who offered their services, were the subjects. At each
day’s sitting 4 half-sheets of the same test were read, and the average time (after correction was made for errors according to the plan outlined
in Experiment 2) was recorded as the day’s score. Only a few errors were left uncorrected. The largest correction made on the practice test
changed the mean from 49.3 to 49.6. The plan of experimentation was as follows:
On the 1st day the RCNb test was used to acquaint the subjects with the experimental procedure and improve the reliability of the 2d day’s
test. The RCNd test was given the 2d day and the 13th day to obtain a measure of the interference developed by practice on the NC and
NCWd tests. The RCNd test was given the 14th day to get a measure of the effect of a day’s practice upon the newly developed interference.
The NC test was given the 3d and 12th days, just before and just after the real practice series, so that actual change in interference on the
NCWd test might be known. The test schedule was followed in regular daily order with two exceptions. There were two days between test
days 3 and 4, and also two between test days 8 and 9, in which no work was done. These irregularities were occasioned by week-ends. Each
subject was assigned a regular time of day for his work throughout the experiment. All but two subjects followed the schedule with very little
irregularity. These two were finally dropped from the group and their data rejected.
All of the tests were given individually by the author. The subject was seated near a window so as to have good daylight illumination from
the left side. There was no other source of light. Every subject was in the experimental room a few minutes before beginning work to allow
his eyes to adapt to the light conditions. To aid eye-adaptation and also to check for clearness of vision each subject read several lines in a
current magazine. Every subject was given Dr. Ishihara’s test for color vision. One subject was found to have some trouble with red-green
color vision; and her results were discarded though they differed from others of her sex only in the number of errors made and corrected.
Results: The general results for the whole series of tests are shown in Table V which presents the means, standard deviations, and coefficients
of variability for the whole group and for each sex separately, together with a measure of sex differences in terms of the probable error of the
difference. Table VI, which is derived from Table V, summarizes the practice effects upon the respective tests. The graphical representation of
the results in the practice series gives the learning curve presented in Fig. 2.
[p. 654]
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The Effect of Practice on the NCWd Test upon Itself
The data to be considered here are those given in the section of Table V under the caption “Days of Practice on the NCWd Test.” They are
also presented in summary in the left section of Table VI and graphically in Fig. 2. From all [p. 655] three presentations it is evident that the
time score is lowered considerably by practice.
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Reference to Table VI shows a gain of 16.8 seconds or 33.9 percent of the mean of the 1st day’s practice. The practice curve is found to
resemble very much the ‘typical’ learning curve when constructed on [p. 656] time units.
The coefficient of variability is increased from .14 ± .012 to .19 ± .015. This difference divided by its probable error gives
2.60 which indicates that it is not reliable. The probability of a real increase in variability, however, is 24 to 1. Hence, practice on the NCWd
test serves to increase individual differences.
An examination of the data of the sex groups reveals a differences in speed on the NCWd test which favors the females. This is to be expected
as there is a difference in favor of females in naming colors. Though the difference is not reliable in any one case it exists throughout the
practice series; indicating that the relative improvement is approximately the same for the two groups. This latter fact is also shown by the
ratio of the difference between the halves of practice series to the first half. It is .185 for the males and .180 for the females.
The Effect of Practice on the NCWd Test upon the NC Test
The middle section of Table VI shows a gain on the NC test of 4.0 seconds or 13.9 percent of the initial score. This is only 23.7 percent of the
gain on the NCWd test which means that less than one fourth of the total gain on the NCWd test is due to increase in speed in naming colors.
The improvement is greater for the males, which is accounted for by the fact that there is more difference between naming colors and reading
names of colors for the males than for the females.
The Effects in the RCNd Test of Practice on the NCWd and NC Tests
The right section of Table VI shows that the practice on the NCWd and NC tests resulted in heavy loss in speed on the RCNd test. A
comparison of the right and left sections of the table shows that the loss on the RCNd test, when measured in absolute units, is practically
equal to the gain on the NCWd test; when measured in relative units it is much greater. It is interesting to find that in ten short practice
periods the relative values of opposing stimuli can be modified so greatly. [p. 657] There is little relation, however, between the gain in one
case and the loss in the other. The correlation between gain and loss in absolute units is .262 ± .11, while the correlation between
percent of gain and percent of loss is .016 ± .17, or zero. This is what one might expect.
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From a consideration of the results of the two applications of the RCNd test given in the final tests of Table V, it is evident that the newly
developed interference disappears very rapidly with practice. From one day to the next the mean decreases from 34.8 to 22.0 seconds. This
indicates that renewing the effectiveness of old associations which are being opposed by newly formed ones is easier than strengthening new
associations in opposition to old well established ones.
The variability of the group is increased by the increase in interference due to practice on the NCWd test. The coefficient of variability
increases from .15 ± .013 to .34 ± .031, the difference divided by its probable error being 5.65. This is not surprising as the
degree of the interference varies widely from different subjects. Its degree is determined by the learning on the practice series which is shown
by the individual results to vary considerably. One day’s practice on the RCNd test reduced the variability from .34 ± .031 to .25
± .022. The decrease in variability is 2.3 times its probable error.
The data from this experiment present interesting findings on the effect of practice upon individual differences. The results which have
already been discussed separately are presented for comparison in Table VII.
[p. 658] These results show that practice increases individual differences where a stimulus to which the subjects have an habitual reaction
pattern is interfering with reactions to a stimulus for which the subjects do not have an habitual reaction pattern (the word stimulus interfering
with naming colors, NCWd test); but decreases individual differences where a stimulus to which the subjects do not have an habitual reaction
pattern is interfering with reactions to a stimulus for which the subjects have an habitual reaction pattern (the color stimulus interfering with
reading words — RCNd test). There are two other variables involved, however: initial variability and length of practice. Thus in the NCWd
test the initial variability was less, the difficulty greater, and the practice greater than in the RCNd test. These findings lend some support to
Peterson’s hypothesis, “Subjects of normal heterogeneity would become more alike with practice on the simpler processes or activities, but
more different on the more complex activities” (Peterson and Barlow, 1928, p. 228).
A sex difference in naming colors has been found by all who have studied color naming and has been generally attributed to the greater
facility of women in verbal reactions than of men. There is some indication in our data that this sex difference may be due to the difference in
the accustomed reaction of the two sexes to colors as stimuli. In other words responding to a color stimulus by naming the color may be more
common with females than with males. This difference is probably built up through education. Education in color is much more intense for
girls than for boys as observing, naming, and discussing colors relative to dress is much more common among girls than among boys. The
practice in naming colors in the NCWd test decreased the difference between the sex groups on the NC test from a difference 5.38 times its
probable error to a difference 2.99 times its probable error. This decrease in the difference due to practice favors the view that the difference
has been acquired and is therefore a product of training.
[p. 659] SUMMARY
1. Interference in serial verbal reactions has been studied by means of newly devised experimental materials. The source of the interference is
in the materials themselves. The words red, blue, green, brown, and purple are used on the test sheet. No word is printed in the color it names
but an equal number of times in each of the other four colors; i.e. the word ‘red’ is printed in blue, green, brown, and purple inks; the word
‘blue’ is printed in red, green, brown, and purple inks; etc. Thus each word presents the name of one color printed in ink of another color.
Hence, a word stimulus and a color stimulus both are presented simultaneously. The words of the test are duplicated in black print and the
colors of the test are duplicated in squares or swastikas. The difference in the time for reading the words printed in colors and the same words
printed in black is the measure of the interference of color stimuli upon reading words. The difference in the time for naming the colors in
which the words are printed and the same colors printed in squares (or swastikas) is the measure of the interference of conflicting word
stimuli upon naming colors.
2. The interference of conflicting color stimuli upon the time for reading 100 words (each word naming a color unlike the ink-color of its
print) caused an increase of only 2.3 seconds or 5.6 percent over the normal time for reading the same words printed in black. This increase is
not reliable. But the interference of conflicting word stimuli upon the time for naming 100 colors (each color being the print of a word which
names another color) caused an increase of 47.0 seconds or 74.3 percent of the normal time for naming colors printed in squares.
These tests provide a unique basis (the interference value) for comparing the effectiveness of the two types of associations. Since the
presence of the color stimuli caused no reliable increase over the normal time for reading words (D / PEd = 3.64) and the presence of word
stimuli caused a considerable increase over the normal time for naming colors (4.35 standard deviation units) the associations that have been
[p. 660] formed between the word stimuli and the reading response are evidently more effective than those that have been formed between
the color stimuli and the naming response. Since these associations are products of training, and since the difference in their strength
corresponds roughly to the difference in training in reading words and naming colors, it seems reasonable to conclude that the difference in
speed in reading names of colors and in naming colors may be satisfactorily accounted for by the difference in training in the two activities.
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The word stimulus has been associated with the specific response ‘to read,’ while the color stimulus has been associated with various
responses: ‘to admire,’ ‘to name,’ ‘to reach for,’ ‘to avoid,’ etc.
3. As a test of the permanency of the interference of conflicting word stimuli to naming colors eight days practice (200 reactions per day)
were given in naming the colors of the print of words (each word naming a color unlike the ink-color of its print). The effects of this practice
were as follows: 1. It decreased the interference of conflicting word stimuli to naming colors but did not eliminate it. 2. It produced a practice
curve comparable to that obtained in many other learning experiments. 3. It increased the variability of the group. 4. It shortened the reaction
time to colors presented in color squares. 5. It increased the interference of conflicting color stimuli upon reading words.
4. Practice was found either to increase or to decrease the variability of the group depending upon the nature of the material used.
5. Some indication was found that the sex difference in naming colors is due to the difference in the training of the two sexes.
(Manuscript received August 15, 1934)
Footnotes
[1] 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 manuscript; 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.
[2] Descoeudres (1914) and also Goodenough and Brian (1929) presented color and form simultaneously in studying their relative values as
stimuli.
[3] In Appendix A will be found a key to all symbols and abbreviations used in this paper.
References
BAIR, J. H., The practice curve: A study of the formation of habits. Psychol. Rev. Monog. Suppl., 1902 (No. 19), 1-70.
BERGSTRÖM, J. A., Experiments upon physiological memory. Amer. J. Psychol., 1893, 5, 356-359.
BERGSTRÖM, J. A., The relation of the interference of the practice effect of an association. Amer. J. Psychol., 1894, 6, 433-442.
BOWDITCH, H. P., and WARREN, J. W., The knee-jerk and its physiological modifications. J. Physiology, 1890, 11, 25-46.
BROWN, WARNER, Practice in associating color names with colors. Psychol. Rev., 1915, 22, 45-55.
BROWN, WARNER, Habit interference in card sorting. Univ. of Calif. Studies in Psychol., 1914, V. i, No. 4.
CATTELL, J. McK., The time it takes to see and name objects. Mind, 1886, 11, 63-65.
CULLER, A. J., Interference and adaptability. Arch. of Psychol., 1912, 3 (No. 24), 1-80.
DESCOEUDRES, A., Couleur, forme, ou nombre. Arch. de psychol., 1914, 14, 305-341.
GARRETT, H. E., and LEMMON, V. W., An analysis of several well-known tests. J. Appld. Psychol., 1924, 8, 424-438.
GOODENOUGH, F. L., and BRIAN, C. R., Certain factors underlying the acquisition of motor skill by pre-school children. J. EXPER.
PSYCHOL., 1929, 12, 127-155.
HUNTER, W. S., and YARBROUGH, J. U., The interference of auditory habits in the white rat. J. Animal Behav., 1917, 7, 49-65.
HUNTER, W. S., Habit interference in the white rat and in the human subject. J. Comp. Psychol., 1922, 2, 29-59.
KLINE, L. W., An experimental study of associative inhibition. J. EXPER. PSYCHOL., 1921, 4, 270-299.
LESTER, O. P., Mental set in relation to retroactive inhibition. J. EXPER. PSYCHOL., 1932, 15, 681-699.
LIGON, E. M. A., Genetic study of color naming and word reading. Amer. J. Psychol., 1932, 44, 103-121.
LUND, F. H., The role of practice in speed of association. J. EXPER. PSYCHOL., 1927, 10, 424-433.
MÜLLER, G. E., and SCHUMANN, F., Experimentalle Beiträge zu Untersuchung des Gedächtnisses. Zsch. f. Psychol., 1894, 6, 81-190.
MÜNSTERBERG, HUGO, Gedächtnisstudien. Beiträge zur Experimentellen Psychologie, 1892, 4, 70.
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PEARCE, BENNIE D., A note on the interference of visual habits in the white rat. J. Animal Behav., 1917, 7, 169-177.
PETERSON, J., and BARLOW, M. C., The effects of practice on individual differences. The 27th Year Book of Nat. Soc. Study of Educ.,
Part II, 1928, 211-230.
PETERSON, J., LANIER, L. H., and WALKER, H. M., Comparisons of white and negro children. J. Comp. Psychol., 1925, 5, 271-283.
PETERSON, J., and DAVID, Q. J., The psychology of handling men in the army. Minneapolis, Minn. Perine Book Co., 1918, pp. 146.
SHEPARD, J. F., and FOGELSONGER, H. M., Association and inhibition. Psychol. Rev., 1913, 20, 291-311.
TELFORD, C. W., Differences in responses to colors and their names. J. Genet. Psychol., 1930, 37, 151-159.
WOODWORTH, R. S., and WELLS, F. L., Association tests. Psychol. Rev. Monog. Suppl., 1911, 13 (No. 57), pp. 85.
Appendix A
A Key to Symbols and Abbreviations
NC
Naming Colors.
NCWd Naming the Colors of the Print of Words Where the Color of the Print and the Word are Different.
RCNb Reading Color Names Printed in Black Ink.
RCNd Reading Color Names Where the Color of the Print and the Word are Different.
D
Difference.
D / P Ed Difference divided by the probable error of the difference.
M & F Males and Females.
P Ed
Probable error of the difference.
s
Sigma or standard deviation.
s / m Standard deviation divided by the mean.
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Neuroscience For Kids – stroop effect
Neuroscience For Kids
Colors, Colors
The famous “Stroop Effect” is named after J. Ridley Stroop who discovered this strange phenomenon in the 1930s. Here is your job: name the colors of the following words. Do NOT
read the words…rather, say the color of the words. For example, if the word “BLUE” is printed in a red color, you should say “RED”. Say the colors as fast as you can. It is not as easy as
you might think!
TRY IT!
Try this Interactive Stroop Effect Experiment. The computer will keep track of the time it takes you to say the colors of the words.
[Run Experiment]
Also available: print out Stroop Test Mini Cards.
Why?
The words themselves have a strong influence over your ability to say the color. The interference between the different information (what the words say and the color of the words)
your brain receives causes a problem. There are two theories that may explain the Stroop effect:
1. Speed of Processing Theory: the interference occurs because words are read faster than colors are named.
2. Selective Attention Theory: the interference occurs because naming colors requires more attention than reading words.
I think that this puzzle would be easier for a very young child than for older children or adults. Try this out on some small kids who know their colors, but cannot yet read! I would
imagine that the children would not get confused by this puzzle because the words would not have any meaning to them.
My scores: Test #1 = 10.1 seconds; Test #2 = 22.4 seconds
It took me more than TWICE the amount of time to read the “confusing” words.
There is some evidence that the anterior cingulate area is active in people during the Stroop effect.
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More experiments to try:
Turn the words upside down or rotate them 90 degrees.
Turn the words “inside out.”
Use non-color words such as “dog” or “house.”
Use nonsense words such as “kiw” or “thoz.”
Compare long words to short words.
Use emotional words such as “sad” or “happy” or “depressed” or “angry.”
Color only half of the word or color only the first and last letter of each word.
The original reference to the Stroop paper is: Stroop, J.R. Studies of interference in serial verbal reactions. J. Exp. Psychol., 18:643-662, 1935. You can even read this complete 1935
paper on the web!
If you would like to use the Stroop Effect as an experiment in class, here is a lesson ready to go.
Other web resources on the Stroop effect:
1. Interference – from the American Psychological Association
2. Stroop Effect – from NOVA
New Stroop Tests
Here are three new variations of the Stroop Effect that you may not have seen.
TRY
IT!
1. Try this Interactive DIRECTIONAL Stroop Effect Experiment. The computer will keep track of the time it takes you to say the LOCATION of the words.
[Run Directional Stroop Experiment]
2. Try this Interactive NUMBER Stroop Effect Experiment. The computer will keep track of the time it takes you to count the number of words. [This “Counting Stroop
Effect” was described originally by Bush, G. et al., The counting Stroop: An interference task specialized for functional neuroimaging–validation study with functional
MRI. Human Brain Mapping, 6:270-282, 1998.]
[Run Number Stroop Experiment]
3. Try this Interactive ANIMAL Stroop Effect Experiment. The computer will keep track of the time it takes you to say the NAME of animals you see.
[Run Animal Stroop Experiment]
Are these new tests easier or harder than the original colored word Stroop Effect? Why?
Did
you
Dr. Stroop left the laboratory not long after he published his studies on his “effect” and joined the faculty at David Lipscomb College, a small Christian college in Nashville,
know? TN. He died in 1973 at the age of 76. Read more about “Brother Stroop” (that’s what his students called him) in Science News, Vol. 141, pages 312-316, 1992. Also, read
about the donation of Stroop’s original thesis to Vanderbilt University.
Copyright © 1996-2020, Eric H. Chudler All Rights Reserved.
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