Instructions for the Stroop Experiment

STUDENTS	INSTRUCTORS
Your instructor may have given you instructions on how to set up your experiment. If so, please use the settings given to you by your instructor.	If you would like your students to do the same Stroop experiment, you will need to give them the settings you want them to use. Download a sample handout.

Background

The Stroop effect is a classic cognitive psychology experiment discovered and first studied by J. Ridley Stroop (Stroop 1935/1992). In this classic study, if the person is trying to name the font color of a word, it takes longer if the word is also a color word, but a different color. So it takes more time to name the color blue if the word is “red”. For example, naming the font color of the word BLUE is easier than naming the font color of the word RED.

Quickstart Instructions

To run this classic study, the link at the bottom of this section will take you to the experiment setup screen.

The default experiment has the two classic conditions of the Stroop experiment: Congruent words, where the color word and the font color of the word match (e.g., BLUE), and incongruent words, where color word and the font color of the word are different (e.g., BLUE). In both conditions of this default experiment, your task is to respond to the font color of the word by pressing a key associated with that color (e.g., if the word is BLUE, you would press "r" for red).

Running the Experiment

At the bottom of the Experiment Setup Screen, press the "Done" button.

The Stroop experiment screen will appear. In the middle of the screen, brief instructions will be presented. Pay careful attention to whether you are to respond to the color of the font or the word itself. Note that the order of the conditions will be randomly determined by the experiment.

Press the button at the top of the page or the space bar to begin the experiment. A fixation mark in the middle of the screen will be presented. It will be removed when the words (or strings of Xs) are presented. When the word (or string of Xs) is presented, respond to the color of the font or the word itself as indicated in the instructions. You can do this three ways:

press the relevant button at the bottom of the experiment screen.
press the following keys: 'r' for red, 'g' for green, 'b' for blue, 'y' for yellow, 'o' for orange, or 'p' for purple.
press the following keys: 'a' for red, 'f' for green, 'j' for blue, ';' for yellow, 'x' for orange, or 'm' for purple.

The stimuli are randomly selected but words are never repeated twice in a row.

At the end of the experiment, your results will be presented, both average reaction time and your accuracy. You can also get your trial by trial results. To submit your data to Online Psychology Laboratory, press the "Submit Data" button at the bottom of the screen. Closing your results window will take you back to the setup window where you can run another experiment using the same settings or select different settings.

Go to the experiment setup screen and start the experiment.

Customizing the Experiment

Students: If your instructor has given you settings to use, please select those when you get to the experiment setup screen.

If you do not change any conditions, your experiment will use the default settings (identified by bold print in the table below).

Figure 1. Image of the Experiment Setup Screen -- Each of these 5 variables is customizable and described in the following table.

Table 1. Setting Options for Each Variable

Variable

Settings (Default settings are in bold print.)

Number of Conditions to Test

1, 2, 3, or 4

Conditions

You may select as many conditions (1 - 4) as you identified above in "Number of Conditions to Test."

BLUE	Congruent Words -- font color and word same
BLUE	Incongruent Words -- font color and word different

XXXX	XXXXColored -- string of X's colored -- only available when you select "Respond to color" (see below)
BLUE	Word White -- only available when you select "Respond to word" (see below)

EULB	Congruent Reversed -- font color and word same but word backward
EULB	Incongruent Reversed -- font color and word different but word backward

BLXX	Beginning Congruent -- first two letters of the color word then x's in congruent color
BLXX	Beginning Incongruent -- first two letters of the color word then x's in an incongruent color

XXUE	End Congruent -- two x's then last letters of word in congruent color
XXUE	End Incongruent -- two x's then last letters of word in incongruent color

BULE	Middle Random Congruent -- first and last letter in correct position, the middle in random order in congruent color
BULE	Middle Random Incongruent -- same as above but in an incongruent color

BELU	End Random Congruent -- first letter in correct position, rest of letters in random position, in congruent color
BELU	End Random Incongruent -- same as above but in an incongruent color

UBLE	Beginning Random Congruent -- last letter in correct position, the rest in random position, in congruent color
UBLE	Beginning Random Incongruent -- same as above but in an incongruent color

(Some conditions are incompatible with other conditions. If you pick a condition that has a response conflict, you will be informed of this situation, and your choice will not be allowed.)

Colors to Use

Choose the colors and the corresponding words used in your experiment.

Red, Green, Blue, Yellow, Orange, and Purple

Respond to What?

Whether the participant is to respond to the color of the font or the word.

Example: BLUE (Respond to the color of the font? "Red" is correct. Respond to the word? "Blue" is correct.)

(Set automatically and not available in conditions XXXXColored, for partial words, and when the words are not colored).

Respond to Color, Respond to Word

Number of Words in Condition

The number of words that will be displayed.

How many words you can display is affected by the number of conditions you choose.

Number of conditions	Number of words to choose from
1	10-45
2	10-45
3	10-30
4	10-20

DEFAULT: 20

Data Format and Download

Once you have completed the experiment, you can download the data. Figure 2. shows the data in Excel.

Figure 2. View of the Data in Excel

References

Stroop, J. R. (1992). Studies of interference in serial verbal reactions. Journal of Experimental Psychology: General, 121, 15-23. (Original work published in 1935).