key release output (case 8986)

I am wondering if DirectRT can provide information on whether the correct key was pressed before measuring the key release time. In the "key release" sample, the data output indicates the time at which the key pressed is released, and the subsequent key pressed & time.

However, there doesn't appear to be any information on whether participants actually press the correct key to begin with (i.e. [I]before [/I]the key release occurs). In the sample, this key would be the spacebar. If I press and release a key other than the spacebar prior to the stimulus, this information doesn't appear to be captured anywhere in the regular data or log files.

Is there a way to verify that participants are pressing the correct key prior to the key release?

Thanks for your help!

Hi cam15,

I think that I may have an answer that meets your needs. I did a slight modification to keyrelease.csv file from the DirectRT Samples folder where I changed the stim value for the "get ready" instruction screen from a 2000 ms display time to requiring that the space bar be pressed to move on (using rt:57). I've attached the file-"keyrelease_spacebarhold.csv" if you would like to look at it and try to run it yourself.

I also attached the log file for a single session that I ran so you can see if this is the information you wanted. You can see that there are two rows recorded for each trial. The first row confirms that the space bar is pressed in response to the "get ready" instructions. The next row will show how long it took to release the space bar, the key pressed, whether it was correct, and the total reaction time to press that new key.

Please let me know if this is what you were looking for or if you were looking for something different.

Cheers.

Jason

Hi Jason,

This is very helpful. Could you run through what the RT output indicates for me? I'm a little confused as to how the output works with multiple rows.

My guess is that...
Started@ = the "Get ready" screen displayed 2521 ms after session onset

[U]Row 1 of log file:[/U]
RT = 1513 ms after "Get ready" screen was displayed, the participant pressed the spacebar

TotalInt = 984 ms between the end of trial 1 and beginning of trial 2 (or is this between stimulus 1 of trial 1 and stimulus 2 of trial 1?)

Time 1 = the "Get ready" screen was cleared 1529 ms after the participant pressed the spacebar

Time 2 = 1546 ms - ??? not sure about this one

[U]Row 2 of log file:[/U]
Release = release of spacebar occurred 1351 ms after __??? (which event/stimulus?)

RT = ??? not sure

The rest of the row is the same as row 1, so I'm guessing you don't interpret this.

If you could clarify what the above output means in the log file w/the key release function, I would appreciate it. Thank you!!

The two rows in the log output file correspond to the two main parts of each row of the input file. The first row for each trial shows the relevant information about displaying the "get ready" instruction and pressing the space bar in response to that stimulus. The "x.01" in the "order" column and the "get ready" in the "Stim" column show that the "get ready" stimulus was indeed displayed first for each trial.

The most important information for this first part of each trial is from your original question about how you can be sure if a participant pressed the space bar at the start of each trial. We need three columns to show that: the "SPACE" value in the "Name" column" shows that the space bar is what is supposed to be pressed (remember the rt:57 in the input file), the "TRUE" in the "Correct" column confirms that the space bar was pressed, and the value in the "RT" column tells you how long it took to press the space bar from the when the "get ready" message first appeared.

The second row for each trial shows what happened for the second part of each of trial; this is reflected in the "x.02" value in the "Order" column. Here, we want to know that the participant started with the space bar pressed, saw a stimulus asking for a key press, that the participant released the space bar, pressed a key, and what key was pressed, if it was correct, and how fast it was pressed. Here is a breakdown of where to find this information:

1) Start with space bar pressed > this is not directly recorded in the data file, but is reflected in the difference between the numbers in the "Release" and "RT" columns. The bigger the difference between these two numbers is how long it took to press a key after letting go of the space bar. DirectRT doesn't accept a key press until the space bar is released; go ahead and give it a try for yourself and notice the corresponding difference in the values in these two columns.

2) Saw a stimulus asking for a key press > this is the value in the "Stim" column of these rows.

3) The participant released the space bar > this is the value in the "Release" column. This is the number of milliseconds that passed between the presentation of the stimulus asking for a key press and when the participant let go of the space bar that they pressed for the first part of the trial. Because the first part of each trial asks for the participant to press a space bar, that is why you see a value of 0 for each of the rows with "x.01" in the "Order" column.

4) What key was pressed > this is the value in the "Name" column. You can see that I pressed the INSERT key for every trial.

5) Was the key pressed correct > this is the value in the "Correct" column. If it is TRUE, the correct key was pressed.

6) How fast it was pressed > this is the value of the RT column. It shows the number of milliseconds that passed between the presentation of the stimulus for this second part of the trial and when the key was pressed. As I said in 1 above, the difference between this value and the value of the "Release" cell in the same row lets you know the number of milliseconds between when the space bar was pressed and the next key that was pressed.

That should give you all of the information that you need for the core parts of this task. If you need information about the other columns, take a look at the Output Files > Log Files _ More Data! section of the DirectRT manual.