Stroop3b Specs
Stats: Greg Zarow
Changes from Stroop3:
* Timing is now based on the onset of the response, rather than on when the response was recognized.
The following are the specs for Stroop3:
Basic Task: This is a Stroop task. On each trial, subjects see a string of letters in one of four colors (Red, Green, Blue, and Yellow). They should be easily discriminable colors against a black background, large letters (about 16 point), centered in a box in the middle of the screen. The box should always remain present.
The subject’s task is to name the color of the ink (not the word) aloud. We are interested in both reaction time and errors.
There are three trialtypes (conditions that vary between trials): compatible, incompatible, and neutral. On compatible trials, the word is the same as the ink color (Red). On incompatible trials, the color and the word differ (Green). On neutral trials, the string consists of five Xs (XXXX).
Just select the ink color randomly from a set of four without replacement. Then if it’s compatible, make the word the same as the ink color. If it’s neutral, make the word XXXX. If it’s incompatible, randomly select one of the three words referring to some color other than the ink color.
There is another factor that varies between blocks. This is the timing of the presentations.
Here is the design. There are 4 blocktypes:
Blocktype Interval
from one trial to the next
1 Fixed 200 msec
2 Fixed 2000 msec
Before starting the experiment proper, have them do ten practice trials all with neutral XXXX’s. This should be done while the experimenter is in the room, to check that the voice recognition is working. We will have some non-native speakers and people who speak very softly so I predict voice recog won’t work on some people.
There should be 10 blocks each composed of 100 trials per block. The blocks should alternate between blocktype 1 and blocktype 2. The subject’s order condition (1 or 2) should determine which blocktype they start with in block 1.
At the end of each block, put up a signal saying “Rest Period – click to resume” and then continue when they click.
Instructions to include in file:
Thank you for participating in our experiment. In this study, you will be seeing colored words or letter string on the screen. Your task is to name the color of the “ink” in which the word is printed as quickly as possible. If you see XXXX you would say “red!”. Sometimes the word will be confusing, e.g., Green. You should also say “red!” to this. We are interested in both speed and accuracy. Try to respond as quickly and as accurately as you can. You will do 10 blocks of trials, each lasting a few minutes. Your task is: as soon a word or letter string appears, just name the color of the ink as quickly and accurately as you can. Everyone makes some mistakes. Try to keep your eye on the box where the words will appear, even when there is a long pause. The blocks don’t last more than a few minutes. If you have any questions, please ask the experimenter now.
File Structure
In the R-file save the block number, trial number, blocktype (Fixed or Variable), trialtype (Compat, Incompat, or Neut), the number of seconds that passed from the previous trial, the word, the ink color, the subject’s response time, and their response identity.
Note on Voice Data
This assumes the voice-recognition is working. I suspect that subjects will often blurt out one thing and correct themselves midstream. Sometimes that will probably produce an unrecognizable combination (“Yell-red!”) and sometimes a sequence of two (“Yellow – no, Red”). If you can save “Unrecog” in the first case, and “Yellow – Correction” in the second, that would be perfect. The trial should be counted as an error in any case. To be counted right they must say the correct word and nothing else.