occasional skips

[philippe goldin]

Uisng Epimre v2, we have also observed that on a slide set to infinite time 
with a button press to terminate that slide, the slide will sometimes 
automatically terminate (without a button press) and advance to the next 
slide.  We have not been able to identify the source of this irrgular problem.

philippe



At 05:27 PM 8/10/2007 +0100, Caren Frosch wrote:
>Leisha Wharfield wrote:
>>Stimulus duration = infinite, Time limit = same as duration, End action = 
>>terminate?
>
>yes.
>
>I have a feeling it could have something to do with the pre-release on the 
>slide that appears prior to the skipped slide. Doruk mentioned something 
>about it and when I read up about it some more I realised that the fact 
>that I have pre-release on a slide which is terminated by response input 
>could be a problem (though it didn't specifically say that this could 
>cause skipping). I've taken the pre-release out and will have to see if it 
>happens again. As the skipping has never happened to me I need to wait for 
>my next participant on Tuesday.
>
>Thank you for your help.
>Caren
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>>Caren Frosch wrote:
>>
>>>I ran a few more participants today. For the first one everything ran 
>>>smoothly. For the second one, the slide that should be presented at the 
>>>end of the practice trial skipped. E-prime recorded the following data 
>>>for that trial:
>>>RT: 0
>>>RESP: (blank)
>>>OnsetTime: 0
>>>
>>>To me that looks like it just skipped, but I cannot work out why. Any 
>>>suggestions?
>>>
>>>Thanks,
>>>Caren
>>>
>>>
>>>
>>>Caren Frosch wrote:
>>>
>>>>Hi Leisha,
>>>>I hadn't been recording any data for those trials as they are only 
>>>>instructions trials, but I've switched it on now. For the last 
>>>>participant where it happened it recorded a RT of 0. The stimulus 
>>>>duration is 'infinite' and the allowable response for this slide is not 
>>>>an allowable response on the task trials.
>>>>
>>>>I'm testing a few more people today. I'll see if I can shed some more 
>>>>light on the issue.
>>>>
>>>>Thanks for your input!
>>>>Caren
>>>>
>>>>
>>>>Leisha Wharfield wrote:
>>>>
>>>>>"It's also not possible that participants are accidentally hitting
>>>>>the key that moves the slide on as I deliberately chose a key away
>>>>>from the keys they are using to respond to the trials (and I don't
>>>>>tell them which key it is)."
>>>>>
>>>>>Do the data bear this out? There are no entries for notaskproc; it 
>>>>>never launches? Have you tried, during testing, prematurely hitting 
>>>>>the key that moves the slide on to see what happens? In my experience, 
>>>>>if there is an unexpected way to proceed through the experiment, 
>>>>>subjects will find it (& that's probably a good thing, because it 
>>>>>leads to refinement).
>>>>>
>>>>>The key that moves the slide on should only be an allowable response 
>>>>>in notaskproc, therefore hitting it prematurely should do nothing. Is 
>>>>>this the case?
>>>>>
>>>>>Leisha Wharfield
>>>>>Decision Research
>>>>>Eugene, Oregon, USA
>>>>>
>>>>>Caren Frosch wrote:
>>>>>
>>>>>>
>>>>>>I'm running an experiment where I have divided a list into four 
>>>>>>blocks, that is, the list consists of 160 trials and after 40 trials 
>>>>>>it leaves the list to run another procedure which consists of one 
>>>>>>slide where participants are told whether or not to generate random 
>>>>>>numbers during the next block (actually one of 3 procedures: 
>>>>>>'taskproc' 'notaskproc', 'endproc'). It's all been running fine. But 
>>>>>>I have found that for some participants it occasionally skips this 
>>>>>>step and they therefore end up doing one big block (consisting of 80 
>>>>>>trials). Has anyone experienced this kind of thing before and do you 
>>>>>>have any suggestions as to what it might be? Could it be a hardware 
>>>>>>problem (e.g. the keyboard)?
>>>>>>
>>>>>>Any suggestions would be much appreciated as I just can't figure out 
>>>>>>why it's doing it. When I run through the experiment myself it's 
>>>>>>always fine. It's also not possible that participants are 
>>>>>>accidentally hitting the key that moves the slide on as I 
>>>>>>deliberately chose a key away from the keys they are using to respond 
>>>>>>to the trials (and I don't tell them which key it is).
>>>>>>
>>>>>>Thank you,
>>>>>>Caren
>>>>>>
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>
>--
>Dr. Caren Frosch
>Research Fellow
>School of Psychology and Clinical Language Science
>University of Reading
>Earley Gate
>Reading
>RG6 6AL
>
>E-mail: c.frosch at rdg.ac.uk
>Phone: 0118 3785538
>


**************************************************************
Philippe Goldin, Ph.D.
Department of Psychology
Stanford University
Jordan Hall, Bldg. 420, Room 126
Stanford, CA 94305

Tel: 650-723-5977
Fax: 650-725-5699
E-mail: pgoldin at stanford.edu
website: Clinically Applied Affective Neuroscience
http://www-psych.stanford.edu/~caan/