Record responses continuously over several trials (case 21114)

Hi,

I am trying to program a simple task. Images are presented one at a time for 400 ms each. They are separated by 200 ms blanks. Sometimes, an image is repeated twice in a row. When that happens, participants need to press the space bar. Any response that is recorded up to 3 seconds after the presentation of a repeated image is correct.

What I did is that I created different trials for each image and each blank. I used the min/max option (0-400 ms for images and 0-200 ms for blanks) and indicated "rt:57,-1,full" in the time column. I indicated that intervals should be of 0 ms.

My problem is that DirectRT does not always record my responses. My hypothesis is that it does not record a response when it is made between trials (i.e., during the intervals that must last at least 60-70 ms). Could that be right? If it is, do you have any suggestions about how I could program the task differently?

Thank you very much!

Catherine

[ATTACH]1842[/ATTACH]

The lack of data recording is most likely due to using a value of 0 in the Trial Interval field of your styles.drt file. This needs to be a non-zero number because it is the amount of time that must pass before your first stimulus of that next trial is displayed. Try using a value like 1000 and running your files again to see if all of the data appears if your run DirectRT. If you have any other questions about the Trial Interval field in the styles.drt file, please refer to this page of the DirectRT manual: [url]http://www.empirisoft.com/directrt/help/directrt_trial_interval.htm[/url]

I would also be happy to help you figure out how to program your task. How many consecutive images are displayed? Does some list keep playing if there is no pair response made? Also, consider using the stimlist feature of DirectRT in configuring the displaying of sets of images. See here in the DirectRT manual: [url]http://www.empirisoft.com/directrt/help/directrt_stim.htm[/url]

Hi Jason,

Thanks a lot for your answer!

If I remember correctly, I did try having longer intervals but I had the same problem. The thing is that I need to record responses for 3000 ms, whereas the images are presented for only 400 ms each and separated by blanks lasting 200 ms. Therefore, I need responses to be recorded during the presentation of 5 consecutive images, [U]including during the intervals separating the presentation of the images[/U] (5*400 + 5*200 = 3000). Is there a way that DirectRT can record responses [U]between trials[/U]?

To answer your questions, I have 12 images that need to be presented 26 times each in a pre-determined order, for a total of 312 image presentations. The images are presented continuously without anything changing when the participant makes a response (except that the response needs to be recorded). Please see the attachment in my first message if you think it can help you understand my task.

Thanks a lot for your help!

Catherine

You can put the 5 consecutive images on the same row of the .csv input file. You can also create a blank screen betwen them by simply typing ~ into a stim cell of that row. You can control the presentation time of the blank screen and allow for screen presses in the same way that you used for the images.

Furthermore, you can use the metacommand feature to limit the timing of that entire row. Take a look at this section of the DirectRT manual for information about the metacommand feature: [url]http://www.empirisoft.com/directrt/help/directrt_samples_v2006_meta_commands.htm[/url]