Investigating the Stroop Effect 1

Title: Investigating the Stroop Effect: How the Congruency of Stimuli Affects

Response Time

Course: 175.102 Psychology as a Natural Science

Assignment: Lab Report Part 1A

Name: Anika O’Connell-Temple

Student Number: 20023303

Student Email Address: oconnellanika@gmail.com

Degree Programme: Bachelor of Arts

Lecturer: Dr. Corinne Bareham-Waldrock

Submission Date: 11:55PM, 9th April 2021

Word count: 1185

 Investigating the Stroop Effect 2

Abstract

The abstract is a summary of the entire report. As the marking guide states, it must
include the background, hypotheses, method, results and conclusions. Use between
150 and 250 words and only one paragraph. Have a look at research articles to see real
examples of this. Delete this instruction and any other instructions that are in gray
writing before submitting your work.

Lorem ipsum, this is just placeholder text to show you where to put your abstract.

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 Investigating the Stroop Effect 3

Investigating the Stroop Effect: How the Congruency of Stimuli

Affects Response Time

The understanding that words are faster to read than objects are to name is
fairly common in experimental psychology. A study executed by Cattell (1886)
highlighted this, it exemplified that the cognitive correlation between a word and the
idea of that word is automatic due to the frequency of its use. Stroop (1935) later
elaborated on this theory with his colour-word test, a neuropsychological exam that
assesses the ability to inhibit cognitive interference, which occurs when the
processing of a stimulus affects the simultaneous processing of another attribute of the
same stimulus. His test consisted of naming the colour of the ink in which the name of
another colour is written. The extra time taken to respond to this type of stimulus
where the ink colour does not match the written word (known as incongruent),
compared to the one used in naming the colour of the control stimuli (for example,
groups of asterisks or coloured shapes), is what is called the Stroop effect.
The traditional and most accepted explanation since Stroop's own formulation
to date has been the speed of processing theory. This theory states that because
reading is faster than naming the colour, the incorrect response will be faster than the
correct one and will interfere with it, resulting in a delay when trying to name the
colour of the ink (Fraisse, 1969). Another possible explanation is known as
automaticity, which implies that recognising and naming colours is not an automated
task whereas reading is, therefore resulting in more attention needed to name a colour
(Macleod and Dunbar, 1988). 
An additional explanation known as the perceptual-encoding account was
presented by Hock and Egeth (1970). Its premise was that incompatible information
from a colour word as opposed to a neutral control delays perceptual encoding of ink-
colour information. However, this theory was objected to by Dyer (1973) who argued
that their conclusions rested on accepting a null hypothesis and the theory has since
been pushed aside.
In its traditional form, the stimuli used in the task were always names of
colours written in a different colour ink, and its response time was compared with that
of a control group (Stroop, for example, used coloured squares). One of the most
important modifications of this original version was made by Klein (1964), whose
fundamental contribution varied the type of words used to manipulate the interference
effect. In his most well-known experiment he used four colours (red, green, yellow
and blue) with which he coloured the following types of stimuli: meaningless
syllables, uncommon words, common words, incongruent combinations of words
whose meaning related to colours (for example, the word lemon in red ink), different
colour names than the four ink colours used, and the names of the four ink colours
used written in another colour. The results showed that, compared with control stimuli
(groups of coloured asterisks), those six types of stimuli not only caused interference,
but said interference gradually increased from the first to the last condition. The
results showed that any stimulus composed of letters (even if it lacks lexical meaning)
causes interference. Additionally, said interference is related both to the frequency
that the words are used and to the degree to which the words suggest a certain colour.
Since Stroops original experiment, there have been many variations made to
test different phenomena. Macleod (1991) provides a comprehensive overview of
variations, including sorting and matching versions, picture versions, as well as
auditory and emotional analogs. This experiment, however, was a replication of that
 Investigating the Stroop Effect 4

of Stroop’s. The aim of the experiment was to investigate how manipulating the
independent variable, which in this case was condition, affects the dependent variable,
also known as response time. The major difference between existing studies that have
investigated the Stroop effect and this one is that we ran it using an online tool called
Qualtrics.
H1: Words presented in the congruent condition will be faster to categorise
than words presented in the incongruent condition.
H2: Fewer mistakes will be made within the congruent condition in
comparison to the incongruent condition.

Method

Participants

A total of 354 participants enrolled in the Massey University course

participated in the experiment. 14 of the participants were excluded because they were
under the age of 17 or did not disclose their age, leaving a total of 340 valid
responses. The mean age of participants was 31.96 (SD = 10.26) and this ranged from
17 to 74. Out of the 340 participants: 57 were male, 278 were female, 2 were
undisclosed, and 3 identified as non-binary. The study did not require ethical approval
but the Massey University Code of Ethics was followed in the design and running of
the study.

Design

The study consisted of a within-subject experiment that used a repeated

measures design. The two-level independent variable was condition, which could
have either been congruent (ink colour matched the written colour name) or
incongruent (ink colour did not match the written colour name). The dependent
variable was response time (how long it took each participant to read the list of words
and identify the colour in which the words were written).

Software

The experiment was designed using a tool called Qualtrics which provides
advanced conditional logic tools that allow for complex experimental designs and
user-tailored survey paths. Given that this is a web-based experiment, the computer
equipment used could not be controlled.
 Investigating the Stroop Effect 5

Procedure

Before the experiment commenced, participants were asked to read through and
agree to a consent form that briefly covered what they were required to do and
explained what the data would be used for. The participants were then given an option
to disclose their age and gender. Next, instructions and an example were provided
which described the activity and how to answer.

The first part of the experiment consisted of a practice block, participants were
provided with 10 exercises where they were asked to identify whether sets of X’s
were written in blue, red, or green using multiple choice selection. The second block
of exercises required participants to identify the ink colour in which the words BLUE,
RED, and GREEN were written. For this set, the condition was congruent meaning
the ink colour matched the name of the colour written (For example, the word RED
written in red ink). The third block of exercises also required participants to identify
the ink colour in which the words BLUE, RED, and GREEN were written, but for this
set the condition was incongruent, meaning the ink colour did not match the name of
the colour written (For example, the word GREEN written in blue ink). Finally,
participants were presented with a simple debriefing message and given their results
which consisted of how long they took to complete the congruent and incongruent sets
of exercises, as well as how many correct answers they had out of 10 for each block.
The manipulation that was used was either to present words in a matching (congruent)
colour, or words in a non-matching (incongruent) colour. The total time that it took to
respond to each list of words was measured.

Results

(Follows on from the Method)

Start with a description of the results. Describe the average response time of the
two lists of words using the mean time (M = xx.xx seconds). Also describe the
variability or spread of the scores using the standard deviation (SD = xx seconds). As
well as describing the effects of the different conditions using numbers (the mean and
 Investigating the Stroop Effect 6

SD) you should also remember to compare these using words: was the congruent
word list faster or slower to respond to than the incongruent list or did the two lists
take the same time on average to respond to? Next you can describe the mean number
of errors and the variability for errors in the same way that you described the response
time. Again remember to describe the difference using words as well as the statistics
(which list had more errors?) Within the results section you should describe your data
but not interpret it. You should remember to refer to your graph and your table by
including a parenthetical statement such as (See Table 1) and (See Figure 1).

Set out table(s) as follows if you use one or more of them. Replace grey print
with your own information in black print. Tables in APA format do not include any
vertical lines between rows or cells of the table (we only use horizontal lines). Make
sure to remember to refer to your tables in your descriptive text.

Table 1

Descriptive Title of Table goes here in italics. You should use a full sentence
and describe simply what the table contains. E.g. “The number of cats and dogs
owned per household in different regions of New Zealand.”

Response Time Errors

Mean (SD) Mean (SD)

IV Name here

Variable Condition 1 x.xx (x.xx) x.xx (x.xx)

Variable Condition 2 x.xx (x.xx) x.xx (x.xx)

Note: Any additional notes providing further information about information in

the table should go here.

In the assignment instructions you are asked to include a table (as above) and a

graph (as below) for your data. Again, make sure to refer to them in your descriptive

text. A couple of sentences about each is wanted.

 Investigating the Stroop Effect 7

Set out your graph (which is called a figure in the APA style guide) as follows.

Delete the one provided, it is there to show you where to place it. Figures can be

constructed in Microsoft Excel (or equivalent) or hand drawn and scanned or

photographed if you prefer.

You will be provided with an Excel workbook that contains some templates for

generating the appropriate kind of charts for this lab report. You can choose whether

you’d like to use a bar/column graph, a frequency polygon graph, or a histogram to

represent the Response Time and the Correct Responses. You can even take the raw

data and use another package that you prefer (some of you will already have a

different favourite chart type (maybe you like box plots, pirate plots, or violin plots).

Figure 1. Descriptive title of your figure goes here in a plain, smaller than normal font.
In this example you would say something about the number of people in each Marital Status.
Also remember to say that you have included an error bar and what it represents (if you use a
plot that has error bars)
 Investigating the Stroop Effect 8

Discussion

(Follows on from the Results)

The Discussion begins with a restatement of your findings in light of what they
tell us about your hypotheses. Go through the hypotheses one at a time in the same
order that you described them in your introduction. Was your hypothesis supported by
the data? If you have not supported your hypothesis then the following paragraph
could then start discussing why this was not the case.

The discussion section always starts very narrow, just with the findings, then
becomes broader as you progress and start discussing whether your data matches
other studies.

Compare and contrast your findings with the studies of other researchers who
have done similar research.

Discuss one or two weaknesses in your current study, what might this weakness
mean as a limitation to whether you can use the data that we have collected to
generalise to other people. How might these limitations affect the way that people
responded. Don’t just criticise your study though—say how you could improve this
study to make the results more useful. Science is about building upon weakness in
past studies to build and constrain theory.

Are there any particular strengths of this experiment? For example, is the way
that we ran this experiment better than other times that a similar experiment was run.
Here you might have to go back and look at things like the number of participants in
other studies, also think about whether it is better to run a replication using a less
controlled procedure (like using a web based tool) compared to a lab run experiment.

Then go on to suggest ways in which future research might build upon your
findings. Here you can be creative. Think of an excellent potential follow-up
experiment or study and briefly suggest it for your reader.

Discuss the theoretical importance of your findings. Have you added to our
existing theory relating to the Stroop effect? Does the replication or failed replication
(we don’t yet know what the experiment outcome is as I write this document) help us
to be more or less confident in the theory relating to automaticity of processing related
to the Stroop effect.
 Investigating the Stroop Effect 9

Finish with a one paragraph conclusion.

Congratulations, all you have left to do now is to make sure that your references
are all APA style formatted. Well done!
 Investigating the Stroop Effect 10

References

Cattell, J. M. (1886). The time it takes to see and name objects. Mind, 1886, 11, 63-

65.

Dyer, E N. (1973). The Stroop phenomenon and its use in the study of perceptual,

cognitive, and response processes. Memory and Cognition, 1, 106-120.

Fraisse, E. (1969). Why is naming longer than reading? Acta Psychologica, 30, 96-

103. 

Hock, H. S., & Egeth, H. (1970). Verbal interference with encoding in a perceptual

classification task. Journal of Experimental Psychology, 83, 299-303. 

Klein, G. S. (1964). Semantic power measured through the interference of words with

color-naming. American Journal of Psychology, 77, 576-588. 

MacLeod, C. M., & Dunbar, K. (1988). Training and Stroop-like interference:

Evidence for a continuum o fautomaticity. Journal of Experimental

Psychology: Learning, Memory, and Cognition, 14, 126-135.

Posner, M. I. (1978). Chronometric explorations of mind. Hillsdale, NJ: Erlbaum.

Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of

Experimental Psychology, 18, 643-662.

 Investigating the Stroop Effect 11

Appendix

(Starts on new page)

If there is only one appendix, just label it Appendix. If there are more then
label them Appendix A, Appendix B, etc.

You could place some additional charts, data analysis, or screen shots of the

procedure here (but it isn’t essential to do so).