Stroop Experiment Software
Overview
The program STROOP runs a version of the Stroop paradigm. On each trial, the subject is presented with a string of
letters printed in color. The subject's task is to respond to the COLOR in which the word is printed by pressing the
correct key as quickly as possible. 
The appropriate key to press for each color is as follows: red = z, green = x, blue
= ., yellow = /. If the response was incorrect, or if an invalid key was pressed, a short tone is presented. Three
conditions are presented in separate blocks. In condition 1 the letter string is composed of X's. In condition 2 the
letter string is the word 'red', 'green', 'blue', or 'yellow' printed in a color different from the named color. In condition
3 the letter string is the name of the color that the letters are printed in. An example of possible stimuli from each condition is shown to the right. Raw
data from the experiment are placed in the file DSTROOP.DAT. An analysis program (STRPANAL) reads the data
file and computes means and standard deviations of the reaction times for correct responses in each of the three
conditions. The output of the analysis is placed in the file ASTROOP.ANL.
Running the experiment
To run the experiment, type STROOP and hit "Enter". When asked to "Press any key to begin", pressing the 'P'
key will allow the user to change various parameters that determine the design of the experiment and the timing of
trial events. Pressing a key other than 'P' will cause the program to begin the first trial immediately. The parameters
that can be safely changed are listed below, along with their probable default values.
1. Number of trials per block (must be multiple of 12):
(default=36)
2. Number of test blocks per session (mult of 3):
(default=6)
3. Number of initial practice blocks under condition 3:
(default=1)
5. Inter-trial interval (msec):
(default=1500)
6. Duration of error tone (msec):
(default=500)
7. Interval between cue and stimulus (msec):
(default=500)
20. Maximum allowed RT (msec):
(default=1500)
Note. The order of conditions across blocks, and the order of trials within a block are determined randomly.
Analyzing the data (You will need analysis program available below)
Simply type STRPANAL and hit "Enter" from the directory in which the experiment was run. When asked
"Number to trim from each end" the user has the option to exclude the desired number of extreme reaction times from
the analysis. Hitting "Enter" will not exclude any data. To view the means from each condition TYPE or PRINT
the file ASTROOP.ANL. If you want to view the raw data, TYPE or PRINT the file DSTROOP.DAT. Each time
that STROOP is run, the program will destroy all previous DSTROOP.DAT data files. Each time that STRPANAL is
run, it will destroy all old ASTROOP.ANL files. Therefore, be sure to look at the data before the experiment is run
again.