Hi guys,
I have a problem and I am very stumped. I am trying to present an array of images for randomized durations of either 400, 600, 800, 1000, 1200, 400 or 1600 ms. Each picture is preceded by a fixation cross and is followed by a mask. Participants then make an alternative forced choice judgment about the length of each stimulus duration (by pressing either the left or right arrow key). There are 50 trials (i.e. 50 pictures shown) in each block. My code, however, does not appear to show the images for the time it says it does (note: when I create a data file for values.fixduration it lies and tells me it is showing the pictures for the correct amount of time).
Here are the relevant bits of the code:
<item trial_items1>
/1 = "1616.jpg"
/2 = "2220.jpg"
/3 = "2385.jpg"
/4 = "2487.jpg"
/5 = "2514.jpg"
/6 = "5532.jpg"
/7 = "6150.jpg"
/8 = "7170.jpg"
/9 = "7182.jpg"
/10 = "7207.jpg"
/11 = "3000.jpg"
/12 = "3102.jpg"
/13 = "3110.jpg"
/14 = "3140.jpg"
/15 = "3150.jpg"
/16 = "3266.jpg"
/17 = "3500.jpg"
/18 = "6230.jpg"
/19 = "6300.jpg"
/20 = "6370.jpg"
</item>
<picture neuneg_picture1>
/items = trial_items1
/select = noreplace
/position = (50,50)
</picture>
<trial neuneg_trial1>
/ontrialbegin = [values.fixduration = replace(400, 600, 800, 1000, 1200, 1400, 1600)]
/ontrialbegin = [trial.neuneg_trial1.insertstimulustime(picture.mask, 200+values.fixduration);]
/stimulustimes = [1=fixation_cross_text; 200=neuneg_picture1]
/validresponse = (203, 205)
/ontrialend = [values.presponse = trial.neuneg_trial1.response]
/ontrialend = [if(values.fixduration <= 850) values.correctresponse = "203"]
/ontrialend = [if(values.fixduration >=851) values.correctresponse = "205"]
/ontrialend=[if(values.correctresponse == values.presponse) values.trialoutcome = 1]
/ontrialend=[if(values.correctresponse != values.presponse) values.trialoutcome = 0]
/pretrialpause = (400)
/recorddata= true
/inputdevice= keyboard
</trial>
<block neuneg_block1>
/trials = [1-49=noreplace(neuneg_trial1)]
</block>
<expt expt_b>
/blocks = [1=practise_block; 2=trial_instructions_survey; 3=noreplacenorepeat(neuneg_block1)
</expt>
I am not sure what is wrong. Especially because the first picture appears to show for the correct time, and then the others do not.
Thanks a bunch in advance!!!!!!