Stroop's Task: An Experiment in Cognitive Psychology
Students in this experiment will look at words and say out loud the color of the ink in which the word is written. Other students will time how long it takes the student to identify all the colors on a list of words. Each list will have a different number of words. No tricks: each word will be written in red, green, purple or blue ink. You just have to name the color.
1. Before you begin, write down your thoughts about this experiment. What kinds of questions do you think we should be trying to answer? What do you expect will happen?
2. Class experiment
Description
Half of the class will read matching lists. On these lists, the words blue, green, black, and red are written in the matching color. Psychologists call these words "congruent." The other half of the class will read nonmatching lists. The same words are written in a color that does not match the word. For example, the word black may be written in red ink. Psychologists call these words "incongruent."
Data Collection Procedures
A checker has the list of the colors for each list. As the students name the colors the checker says "no" if they don't name the right color and the student must name the correct color before proceeding to the next word. The checker also says "start" and "done" for the timer. One student uses a stopwatch to find the total time required to name all the colors on each list. A recorder fills out the attached data collection sheets on the overhead and each student copies the data onto their own sheets.
Data Analysis
Students will construct scatter plots of length of the list versus time for the matching and non-matching lists. Using a piece of spaghetti, students will draw a line that they feel best represents their data. Students will calculate the slope and y-intercept for their line and write the equation for their line in slope-intercept form. They will use the equation or graph to interpolate and extrapolate from their data.
Data Analysis Directions (Do the following for both matching and non-matching data.)
1. Construct a scatter plot for your data, using the length of the matching list in column A (x) and the time in column B (y). Put the length of the non-matching list in column C (x) and the time in column D (y). Note: When you are setting up your chart, choose axes, select x-axis, and set the minimum to 0 and the maximum to 25. This will allow you to see the y-intercept on your scatter plot. Include a heading at the top of column A and column C that identifies the different experiments.
2. Draw a line that you think fits these points the best.
3. Identify two easy to read points on your line. Use these points to compute the slope of your line. What are the units of measure for the slope? What does the slope of this line mean?
4. Identify the y-intercept from your graph. What does the y-intercept mean in this experiment? Does this match what you think it should be? Explain any differences.
5. Write the equation of your line in slope-intercept form on the line on the scatter plot.
6. Interpolate (finding a value between two data points) using your graph or your equation: How long would it take to read a list of 19 colors that match the word? How does this compare to a list of 19 colors that do not match the word? How long would it take to read a list of 10 colors that do not match the word? How does this compare to a list of 10 colors that match the word?
7. Extrapolate (estimating beyond your data) using your graph or your equation: How long would it take to read a list of 25 colors that matched the word? How long would it take to read a list of 25 colors that did not match the word? How are these different?
3. Individual Experiments: Supposing you were J. R. Stroop (the cognitive psychologist who designed this experiment), what questions do you still have about this experiment? Design your own experiment to answer a specific question related to the class experiment. Perform your experiment on your family or friends. Follow the format for the class experiment, analyze your own data and compare it to the data collected in class.
4. Your report: Organize the report using an experiment format: (Use the bold titles as headings in your report.)
Investigation Question (What are you investigating? Be specific: address both the class experiment and your individual experiment.)
Hypothesis (What was your guess to answer your question(s) before you did your experiment?)
Method (Description of how your experiment was done)
Data (Organized in tables and scatter plots)
Data Analysis (Follow the directions above for data analysis. You must do those items at a minimum. You may add additional information if you like. What are the similarities and differences between the two different experiments?)
Conclusions (Can you answer your original question? How does it compare to your hypothesis? Are the results of the matching and nonmatching experiments what you had expected? Why do you think these results occurred? What would you change if you did another experiment? What did you learn?)
Before you hand in your report:
1. Review the rubric. How does your report measure up against the criteria?
2. Make sure you addressed all the topics in the data analysis directions.
3. Check that this is your own very best work.
References:
Hadley, William S., "Experiments from Psychology and Neurology", Mathematics Teacher, Vol 89, No 7, October 96, pp 562-565.
Bower, Bruce, "Brother Stroop's Enduring Effect", Science News, Vol 141, May 9, 1992, pp 312-313, 316.
MacLeod, Colin M., "The Stroop Effect", Psychological Bulletin, Vol 109, m March 1991, pp 163-203.
Incongruent (non-matching) Lists
Data Collection Worksheet
Matching Experiment
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Nonmatching Experiment
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