video being randomly skipped (case 6812)

I'm running an experiment which involves presenting a series of video and STRT during presentation. The design is: 2 short practice videos (< 1 min) at the beginning, followed by 4 experiment videos: stm1, stm2, stm3, stm4 (length ranging from 7 to 10 minutes) in this exact order. There is a black screen (with "continue" button on the bottom) inserted between every two adjacent videos. What happened sometimes in the experiment is that after showing the two practice clips, medialab went straight to stm2 and started showing from there through stm4 while the entire first video (stm1) was skipped. We are using 6 laptops for this experiment and although this problem has affected 5 up to today, it's never consistently associated with any one of them. At one time, medialab is performing fine with the presentation on all laptops; at another time, one laptop will give me trouble by skipping a video and at yet another time, the same problem will occur to a different laptop. It also seems random as to which video the program chooses to skip. Most of the time it was the first video, but I have had two incidents when the third video (stm3) was missed, one incident when the last video (stm4) was missed, and another incident when both stm1 and stm3 were skipped during presentation. Any idea about what might be going on? Our Medialab is the 2006 version. Thank you very much in advance!

Can you post a copy of your que file?

Thank you for your reply. Here it is.

Your input file looks fine. Can you also attach a zipped copy of an entire "data" folder from one of these machines so I can take a look at the output it's producing?

Here is the data collected from one of the computers. First video was skipped on subject 003, and both first and third video were missed on subject 016.

Oh, it's the probe data that is misssing, not the data from the regular medialab data files? In that case what may be happening is you have one probe running into another--this can happen if the probe durations can overlap and the subject does not respond to the first (or [I]n[/I]th) before the next one ([I]n[/I]th + 1). This can cause some chaos because the probe routine no longer know which probe is being responded to. I would have to see your probe input file to see, but that's my first hunch.

Hi, thanks again for your reply. I'm not sure though I quite understand what you said. The STRT data is the only data that's being collected throughout the videos, although we told our subjects that their primary task is to watch the video and secondary task is to respond to the beep tones whenever they hear one. We don't have a regular medialab data file. Also, I tried running the experiment on myself many times and if I missed a few beeps or ignored the STRT task altogether, later on the data file I saw "-1.00" values for whatever I missed rather than 0.00s, which seemed to be the values associated with the skipped video(s). I'm attaching the csv file here. Please let me know if you see anything wrong in it. Thank you!

Hello,

I saw your post and was hoping you could help me. We're running an experiment in which people are watching commercials and responding to an auditory probe. The probes are working just fine but all of our data in the resulting probes.sav file shows up as -1 for the var_t, var_k, and var_r variables. We've tried different probe parameters with no success. We have changed the key instructed to be pressed from space bar to K?, but still no luck.

Were you able to find a solution during your experiment?

Russell

Russell,

Did you ever find a solution to your use of probes?