Hi,

I have this issue. I need to vary presentation time within a trial based on the accuracy of participant's responses. The thing is that I need to find a perceptual threshold for each individual participant. So within this trial:

<trial thresh_setup>

/ stimulustimes = [1 = fixation; 1001 = mask1; 1302 = noreplace(CS_neg, non_words); 1903 = mask2; 2204 = rect, Q_word, P_nonword]

/ validresponse = ("q", "p")

/ correctresponse = ("q")

</trial>

I am starting with 600 ms presentation of 'CS_neg' or 'non_words'. If a participant correctly answers, I need to reduce the presentation time by 50ms. And this reduction by 50ms should follow until participants cannot give a correct answer at the specific presentation duration, which would approximate their individual perceptual thresholds.

Can you give me any hints how to do that?

All the best,

Robert

You need to use the <trial> element's setstimulustime(), insertstimulustime() and resetstimulusframes() functions to do this.

Thanks, Dave! Helpful as always