The Stroop Test: Teacher Overview

Objectives

  • The interpretation of linear equations obtained from data
  • The use of these equation in marking predictions, interpolation and extrapolating
  • Comparison of related data sets
  • Finding a linear equation from the coordinates of points
  • Manipulating linear equations

Materials

  • 3 stop watches
  • graph paper
  • rulers
  • Stroop overheads
  • Uncooked spaghetti

Directions

The teacher places one list on the turned-off overhead projector without letting the subject know whether the list is matching or nonmatching. The teacher makes sure the timers and the subject are ready and turns on the projector. The student must immediately state the color of the ink for each word as quickly as possible. A mistake should be corrected before the student moves on. The timers keep time from the moment the overhead is turned on until the list is completed. A dry run is helpful in letting all students understand the procedure.

Perform the experiment 20 times, matching lists, 10 nonmatching lists. Repeat some of the lists to have multiple points for the same list. Order matching and nonmatching lists randomly so as not to give a student the advantage of knowing beforehand.

If a student becomes flustered and takes an inordinate amount of time to complete a list, discuss the concept of an outlier and discuss the effect of such a data point on the analysis.

Starting with the matching data, have the students plot the points. Discuss how the average time is the dependent variable (y) and the list length is the independent variable (x). Plot the points on the transparency grid at the same time the students do. Using the spaghetti, ask a student to place it so that it best fits the data. Allow some discussion. As soon as the class decides on the best placement, have the students draw in the line with their rulers. Repeat the point plotting with the nonmatching data but use small squares instead of dots.

Have the students write the equations of the two lines using slope intercept form. Estimate the slope and y intercept for each. Using the graphing calculators, enter the data and compute a linear regression on one of the data sets. How close was your equation to the one the calculator found?

Have the students finish their worksheets.

The Stroop TestName______

One of the main uses of data is to make predications about real-world situations. We are going to perform an experiment from cognitive psychology, which is the branch of psychology that tries to understand and explain how the human brain works. The experiment is named after thee man who first performed it, J.E Stroop.

  • Each student will look at a list of color word -red, green, black, or blue. Each list is a

different length. Each word will be written in red, green, black, or blue ink.

  • The student will be asked to say the color of the ink for each word. The time needed to completed each list will be recorded by three timers and the average noted.
  • Two different list will be used: one on which the color of the ink matches the color word, for example, red written in red ink, and a second on which the color of the ink does not match the color word, for example, red written in blue ink. The first type is called matching, the second, nonmatching.

Answer the following questions before we begin:

  1. What do you think we’ll find when we perform these experiments how will the matching

data differ from the non-matching data?

  1. What question would a cognitive psychologist be trying to answer by performing the

experiments?

  1. Why do we use three timers? Wouldn’t one suffice?

Matching NonMatching

List Length / Time 1 / Time 2 / Time 3 / Avg Time / List Length / Time 1 / Time 2 / Time 3 / Avg Time

Graphing

  • Construct a graph that displays the points for the matching experiment using dots for your points. Graph the length of the list on the horizontal axis and the time on the vertical axis.
  • Draw a line for the matching data that best fits these points. It should pass as close to the data points as possible, with some points above and other below
  • Repeat this procedure for the nonmatching data points but use small squares instead of dots.

Equations

Find the equations of your lines in slope intercept form (y = mx + b).

y = ______(Matching)y = ______(Nonmatching)

Graphing Calculators

Using the graphing calculator, enter list length into L1 and the average time into L2 using the matching data. Perform a linear regression and record the equation you found. Repeat for the nonmatching data.

y = ______(Matching)y = ______(Nonmatching)

How close are these to your equations?

Discussion

  1. What are they y-intercepts of your lines? In what unit are they measure?

What would these points mean to a cognitive psychologist?

  1. What are the slopes of your lines? Compare these slopes and discuss what that would mean to a cognitive psychologist.
  1. Making predictions: using your graphs or your equations, estimate how long it would take to name the colors in a list of 25 words. How long would it take for 10 words? Explain how you arrived at these conclusions.
  1. Using your equations, estimate how may words you could name the color of in two minutes. Explain…
  1. Using your equations, estimate how many words you could name the color of in one hour, in one day, in one year. What are you assuming? Do you trust the answers you obtained? Why or why not?
  1. What conclusions would cognitive psychologist draw from this experiment?

Discussion

  1. What are they y intercepts of your lines? In what unit are they measure? What do these points mean to a cognitive psychologist?
  1. What are the slopes of your lines? Compare these slopes and discuss what that would mean to a cognitive psychologist.
  1. Making predictions: using your graphs or your equations, estimate how long it would take to name the colors in al list of 25 words. How long would it take for ten words? Explain how you arrived at these conclusions.
  1. Using your equations, estimate how may words you could name the color two minutes. Explain…
  1. Using your equations, estimate how many words you could name the color in one hour, in one day, in one year. What are you assuming? Do you trust the answers you obtained? Why or why not?
  1. What conclusions would cognitive psychologist draw from this experiment?

Matching NonMatching

List Length / Time 1 / List Length / Time 1