Paper 2 Roadmap: Stroop
Overview:
Paper 2 introduces the nuts and bolts of another classic experimental psychology paradigm, the Stroop
effect. Again, data collection will occur on computers. Each student will complete a 5-10 minute Stroop
experiment. The data will be analyzed and reported in a full APA style research report.
The main goal of this experiment is to provide a concrete example of a 2×2 Factorial Design. As well, we
will learn to relate theory and data. You will be taught about the horse-race model of Stroop, and you will
use this model to predict the data from the class experiment.
The class experiment has two goals. First, to replicate the Stroop effect. Second, to test a manipulation that
will reduce the size of the Stroop effect.
Stroop effect: Incongruent items- congruent items
In this case, the manipulation will be task. For half of the trials, you will identify the color, and for the other
half, you will identify the word.
In your research paper, you will be required to introduce the Stroop effect and explain the horse race model.
You will explain how the horse race model can predict which task will lead to the largest Stroop effect.
Finally, you will describe the methods and results. The results will be reported in a figure and a table.
NOTE: When you report the results, you MUST report all main effects, the interaction, and any necessary
posthoc tests.
Things you will learn:
Using reaction time as a dependent measure
2×2 Factorial designs
Reading and citing primary source material
Predicting data based on a theory
Control in experimental design
Background on the Stroop paradigm:
The Stroop paradigm involves the identification of a bi-valent stimulus. For example, you could be
presented with a word that is written in a particular color. Dimension 1 is the word (e.g., BLUE), and
dimension 2 is the color (e.g., RED). The resulting stimulus would look like this: BLUE. In this case, the
word and color do not match; this is called an incongruent stimulus. A congruent stimulus occurs when the
word and color dimension match (e.g., BLUE). In a standard Stroop experiment, you would be presented
with these kinds of congruent and incongruent items. The task usually involves identifying the color
dimension as quickly as possible while ignoring the word. The Stroop effect itself finds that reaction times
to determine the color dimension are faster for congruent trials (when the word matches) than incongruent
trials (when the word mismatches). The effect is interesting because people cannot ignore the word
dimension even though it is not part of their task. The Stroop effect is usually used to measure your ability
to attend to information in your environment selectively. The review paper by Macleod (1990) demonstrates
the popularity of Stroop research, and the many different ways that this task has already been studied.
Background readings:
Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental
Psychology, 18, 643-662.
Macleod, C. M. (1991). Half a century of research on the Stroop effect: An integrative review.
Psychological Bulletin, 109, 163-203.
-Pages 187-188 describe the horse-race model (it is termed the relative speed of processing account).
Writing the paper
1. Use the same general APA formatting rules that you learned in Paper 1.
2. Create a suitable title for the paper
Abstract
-no more than 250 words (between 150-250 words)
-The aim is to very briefly describe the main experimental aims, how they address the theory at hand, and
the basic pattern of results and conclusion.
The introduction (around 2 double-spaced pages)
The goal of the introduction is to put the research into a broader context and then narrow the focus to
describe the specific research aims.
A. Opening section: (starting broad) about 1 paragraph
-Define the general problem of selective attention.
-Give an anecdote that describes a real-world situation involving the need to select task-relevant from
irrelevant information
-Link this real-world situation to the Stroop paradigm (this provides an argument that the Stroop paradigm
can be used to understand how selective attention works.)
B. Middle section: (discussing prior work, previous articles)
-Define the Stroop paradigm (1-2 paragraphs) Cite Stroop (1935)
-Describe the basic features of a Stroop experiment
-Describe the assumptions of the horse-race model (1-2 paragraphs)
-e.g., the model assumes color and word information have different processing times Mention that the
purpose of the experiment is to test predictions of the model.
C. Final section: (narrowing down to the aims of the experiment)
-Explain that the specific aim of the experiment is to test the horse-race model of the Stroop further effect.
-Briefly describe the independent variables that will be manipulated Congruency (congruent vs.
incongruent)
-Task (color vs. word)
-Does the model predict a main effect of congruency?
Rationale behind the hypothesis!
-Does the model predict a main effect of task?
Rationale behind the hypothesis!
-Does the model predict an interaction between Congruency & Task?
Rationale behind the hypothesis!
-Briefly explain what participants will do in your experiment.
Concerning the last part of the rubric, as I mentioned, there are
three hypotheses you need to emphasize:
For the main effect of congruency, whether reaction times for
incongruent items are expected to be longer than those for congruent items.
For the main effect of the task, whether reaction times for the
color tasks are expected to be longer than those for the word task.
For the interaction effect between congruency and task, whether
reaction times for the difference between the incongruent and
congruent items for the color task are expected to be bigger than the
difference between those for the word task.
In terms of automaticity and selective attention, you
need to clarify why you expect each hypothesis to be based on the Horse Race Model. This will
explain the rationale behind each hypothesis.
Methods (1-2 pages)
The methods section should be a complete recipe that anyone could follow to replicate your experiment. At
the same time, you should be as brief as possible.
-Participants
-How many people- Where did they come from?
Materials
Link
How many words, how many colors
How were they combined to make congruent and incongruent items
How many congruent items
How many incongruent items
Stopwatch/ timer
-Refer to Appendix A and Appendix B
-Procedure
-The research design (within or between), IVs, DV, levels of IVs?
-Describe the trial-sequence
Results
The result section is used to report the patterns in the data and the statistical support for those patterns. Refer
to the lab manual for help on reporting statistics from a factorial design.
Describe the statistical analysis
e.g., mean RTs from each condition were submitted to a 2 (Task: word vs. color) x 2 (congruency:
congruent vs. incongruent) Two-way ANOVA with repeated measures.
-Tell the reader where they can see the data.
-e.g., the results of experiment 1 are presented in Table 1 and in Figure 1
-You will have to make a table or figure to display the data in your paper
Describe the pattern of each main effect
-The main effect of the task was
-The main effect of congruency was
-Describe the Congruency X Task interaction
Discussion
The discussion can briefly restate the pattern of the most important results and then relate the results to
theory and ideas developed in the introduction.
a. Introduction to the discussion (Paragraph 1)
Summarize the results (the main effect of task, the main effect of congruency, the interaction effect between
task and congruency) in everyday, easy-to-understand language.
(No statistics, no numerical values! Just a summary of the main findings)
b. Interpretation of the results (Paragraph 2)
Discuss how the Horse Race Model can explain the data.
Discuss whether or not the model accurately predicted the patterns of data.
Discuss whether the results have been interpreted concerning the hypothesis
Explain whether the present findings are consistent with the previous studies (Macleod, 1990; Stroop,
1935).
Compare your findings with the previous research findings. Please explain how your results are similar to
the previous research findings (e.g., Stroop, 1935) and how they differ from them! If they differ from the
original paper, we replicated and explained how they are different and why.
c. Further discussion (Paragraph 3)
Discuss the possible limitations and potential problems with the current research (e.g., order effect, practice
effect, lack of counterbalancing, lack of random assignment of the order of tasks, and other potential
confounds).
Discuss the shortcomings of your study.
Were there problems with the stimuli, testing conditions, previous participant experience that could have
affected the outcome?
Does this finding create new questions? Clarify future directions.
References
-Include citations used in the paper
Table
Figure
Appendix
