Millisecond Forums

Hello there,

I have a question concercing the AAT. I modified the AAT script (see attachment). Now I conducted a pretest with 10 participants. Every participant had 10 pratice trials (grey rectangles) followed by 80 „real“ trials. The real trials were as followed: 2 groups of stimuli (20 highcaloric pictures vs 20 lowcaloric pictures) x 2 formats (every picture was presented once in portrait and once in landscape format). I have choosed „no replacement“ and a random order so that every stimuli should be presented once (40 highcaloric pictures in boths formats and 40 lowcaloric pictures in both formats). This means that having 10 participants, 800 reals trials should be run. And every „picture-format“ should be presented 10 times. I hope this is understandable.

Now I have analyzed the data and I saw that there are some pictures that are presented 11 times and some that are presented 9 times (see attachment). This would indicate that some participants have seen some stimuli twice and other stimuli not at all.

I am wondering why? Do I have an error in my syntax? In the old topic (https://www.millisecond.com/forums/Topic20225.aspx.) Dave gave me the hint  „Remove the invalid categories (5 to 8) from <list stimcats>“.
Now I realized that in the final version of the sequence generator, I haven’t deleted the categories 5 to 8 in the snytax. Could it be because of that that I didn’t get a balanced numbers of trials?

It would be really nice if someone could help me out.

Thanks a lot,