This is called the Stroop effect or the Stroop task named after J. R. Stroop, who developed the experiments based on this task in the 1930s. With the Stroop task, you are confronted with an interference situation: on the one hand, the word spells out a particular color, such as red; on the other hand, the color of the word is a color such as green. Since reading is so highly practiced, it is hard to suppress the spelled-out word and report the color name.

On the following page, we present an experiment that makes use of the Stroop effect. In this experiment, you will be given two blocks of trials. In both blocks, you need to type the first letter of each color name. If the word is printed in red, hit the letter 'r.' Remember, it doesn't matter what the word says. If you see red, type the letter 'g' because it is the first letter in the color name, green.

Please respond as quickly as possible, though you should try not to make mistakes. This is a reaction time experiment: the object is to test your reaction time to a problematic stimulus.

Each block of trials will have the following sequence:

1. First you will be given a very brief set of instructions which recapitulate the instructions given here. Once you have read these instructions, you hit a key.

2. Following the instructions are two sets of trials, 20 trials in each set. At the beginning of each block of trials, there will be a prompt which waits for you to hit a key in order to proceed to the trials for that block. Each succesive trial begins only after you have responded to the last one.

3. Once you have completed both blocks of trials, a box will come up with a link to a temporary results page. This page is generated from your data, and you may wish to save the results to a local file or print them out for later reference.

NOTE: you will be pressing the following keys: 'r', 'b', 'g' 'y', 'p', and 'o'. We suggest you place your fingers on the normal "home" keys and type the letters as quickly as possible from there.