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As far as I am concerned, typically one error vector is sufficient and more or less the "standard". One might consider modeling different error vectors if the assumption is that, let's say, incompatible errors differ from compatible ones, e.g. in such they are committed faster (please note that I made that up for the example). If you are not going to look at the errors, I'd leave them in one vector, which in your case would result in 5 total. I'd be interested if there are other opinions on this, though. Hope that helps, Franziska -- Franziska M. Korb, Ph.D. Postdoctoral Associate (Egner Lab) Center for Cognitive Neuroscience LSRC Building, Room C03D, Research Dr Box 90999 Duke University Durham, NC 27708 phone: ++1-919-684.1034 http://sites.google.com/site/egnerlab/ On 6/15/2011 3:12 PM, Gaab, Nadine wrote: > > Thanks! One follow-up question: If I have 4 conditions (let's say: > congruent, incongruent, neutral, fixation), do I model 8 (4 conditions > x correct and incorrect) or 5 (four conditions correct plus one with > all incorrect trials)? Thanks, nadine > > -- > > "If we knew what it was we were doing, it would not be called > research, would it?" A. Einstein (1879-1955) > > Nadine Gaab, PhD > > Assistant Professor of Pediatrics > > Harvard Medical School > > Member of the Faculty of Education > > Harvard Graduate School of Education > > Children's Hospital Boston > Department of Medicine > > Division of Developmental Medicine > > Laboratories of Cognitive Neuroscience > Office 611 > 1 Autumn Street, Mailbox # 713 > Boston, MA 02115 > > [log in to unmask] > <mailto:[log in to unmask]> > > phone: (857)-218-3021 > > Main Lab: 617-355-0400 > > fax: 617-730-0518 > > http://www.childrenshospital.org/research/gaab > > or check out: > > http://www.childrenshospital.org/research/gaablab > > or take a look at our new study for INFANTS: > > www.babymri.org <http://www.babymri.org> > > *From:*MCLAREN, Donald [mailto:[log in to unmask]] > *Sent:* Wednesday, June 15, 2011 2:21 PM > *To:* Gaab, Nadine > *Cc:* [log in to unmask] > *Subject:* Re: [SPM] regressor versus condition for incorrect responses > > Nadine, > > It is recommended that you model the two event separately. You'll have > a correct condition and an incorrect condition. > > The general idea of modelling is to model as much of the variance as > possible in the signal, since you know that you have two types of > conditions, you should model both. > > Best Regards, Donald McLaren > ================= > D.G. McLaren, Ph.D. > Postdoctoral Research Fellow, GRECC, Bedford VA > Research Fellow, Department of Neurology, Massachusetts General > Hospital and > Harvard Medical School > Office: (773) 406-2464 > ===================== > This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED > HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is > intended only for the use of the individual or entity named above. If the > reader of the e-mail is not the intended recipient or the employee or > agent > responsible for delivering it to the intended recipient, you are hereby > notified that you are in possession of confidential and privileged > information. Any unauthorized use, disclosure, copying or the taking > of any > action in reliance on the contents of this information is strictly > prohibited and may be unlawful. If you have received this e-mail > unintentionally, please immediately notify the sender via telephone at > (773) > 406-2464 or email. > > > On Wed, Jun 15, 2011 at 2:15 PM, Gaab, Nadine > <[log in to unmask] > <mailto:[log in to unmask]>> wrote: > > Hi list! We have a quick question. We are analyzing an event-related > design in SPM8 and have correct and incorrect responses. We don't care > about the incorrect responses and would like to model only the correct > responses. Do people recommend doing this via a regressor (with 0 for > incorrect and 1 for correct responses) or by modeling the incorrect > and correct responses as separate conditions (but ignore the incorrect > responses in the contrasts)? > > Thanks > > Nadine > > -- > > "If we knew what it was we were doing, it would not be called > research, would it?" A. Einstein (1879-1955) > > Nadine Gaab, PhD > > Assistant Professor of Pediatrics > > Harvard Medical School > > Member of the Faculty of Education > > Harvard Graduate School of Education > > Children's Hospital Boston > Department of Medicine > > Division of Developmental Medicine > > Laboratories of Cognitive Neuroscience > Office 611 > 1 Autumn Street, Mailbox # 713 > Boston, MA 02115 > > [log in to unmask] > <mailto:[log in to unmask]> > > phone: (857)-218-3021 <tel:%28857%29-218-3021> > > Main Lab: 617-355-0400 <tel:617-355-0400> > > fax: 617-730-0518 <tel:617-730-0518> > > http://www.childrenshospital.org/research/gaab > > or check out: > > http://www.childrenshospital.org/research/gaablab > > or take a look at our new study for INFANTS: > > www.babymri.org <http://www.babymri.org> >