Randomising the Fixation duration

[Michiel Spape]

Hiya,
There's indeed nothing wrong with the code, but yes, it's more elegant to do David's suggestion, because you're at least sure it's also logged. There is also good reason to do the nested list with Duration, because you're never quite sure whether "random" isn't too random for your purposes. Suppose, for instance, that you constantly show each and every subject really short fixations? That will make an utter mess of your jittering purposes! It's unlikely, but still possible nonetheless - the joy of randomising with replacement. So, indeed, if you have a nice nested list with every random value (you can safely skip a few, because of screen refresh rates), you can be safe in the knowledge that at least you're sure no value is used twice (depending on the length of the list and the number of trials, of course). 

Best,
Mich


Michiel Spapé
Research Fellow
Perception & Action group
University of Nottingham
School of Psychology
www.cognitology.eu

Michiel Spapé
Research Fellow
Perception & Action group
University of Nottingham
School of Psychology
www.cognitology.eu


-----Original Message-----
From: e-prime at googlegroups.com [mailto:e-prime at googlegroups.com] On Behalf Of David McFarlane
Sent: 31 May 2011 15:57
To: e-prime at googlegroups.com
Subject: RE: Randomising the Fixation duration

Stock reminder:  1) I do not work for PST.  2) 
PST's trained staff takes any and all questions 
at 
http://support.pstnet.com/e%2Dprime/support/login.asp 
, and they strive to respond to all requests in 
24-48 hours -- this is pretty much their 
substitute for proper documentation, so make full 
use of it.  3) If you do get an answer from PST 
Web Support, please extend the courtesy of 
posting their reply back here for the sake of others.

That said, here is my take...

First, I agree that you would do well to work 
through Mich's E-Primer, as well as the Getting 
Started and User's Guides that came with E-Prime.

Now, the inline code method allows you to easily 
randomize down to the ms, and without using 
attribute references.  OTOH, the lack of an 
attribute reference means that the data log 
contains no record of the randomized fixation 
duration.  So I would modify Mich's example as follows:

c.SetAttrib "FixDur", Random(1500,3500)

Then, in my fixation object, I would set Duration to "[FixDur]".  Done.

But if you don't mind (or even prefer) a coarser 
grain (say, 1500 - 3500 ms in steps of 100 ms) 
then you can accomplish this without any inline 
code.  Just use a List, or perhaps a nested List, 
to hold all the possible fixation durations, and 
set the List Selection to Random.  Suppose we 
call that attribute (i.e., column) 
"FixDur".  Then, as before, in your fixation 
object set Duration to "[FixDur]".  Done.  (For 
more on nested Lists in particular, see Appendix 
C of the User's Guide that came with E-Prime.)

-- David McFarlane, Professional Faultfinder


At 5/31/2011 10:26 AM Tuesday, Michiel Spape wrote:
>It's actually somewhere in the E-Primer: 
>http://www.cognitology.eu/pubs/AnE-Primer2009.pdf 
>  as an example of what to do with line-in 
>stuff... I suggest going through the last 2 chapters, or earlier.
>But, then again, if you have a textdisplay 
>showing just a +, called FixationDisplay, and a 
>short inline before that: 
>FixationDisplay.Duration = Random(1500,3500) - you're done.
>Best,
>Mich
>
>Michiel Spapé
>Research Fellow
>Perception & Action group
>University of Nottingham
>School of Psychology
>www.cognitology.eu
>
>-----Original Message-----
>From: e-prime at googlegroups.com 
>[mailto:e-prime at googlegroups.com] On Behalf Of Krupa Sheth
>Sent: 31 May 2011 14:34
>To: E-Prime
>Subject: Randomising the Fixation duration
>
>Hi! I been totally baffled by this and I am sure there is a way where
>to over come this.
>
>Is there any function in E-Prime that allows the fixation point ("+")
>to appear for a random duration between 1500ms to 3500ms. I am sure it
>is possible but am so clueless how to do it.
>
>Many Thanks!!

-- 
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To post to this group, send email to e-prime at googlegroups.com.
To unsubscribe from this group, send email to e-prime+unsubscribe at googlegroups.com.
For more options, visit this group at http://groups.google.com/group/e-prime?hl=en.

This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please send it back to me, and immediately delete it.   Please do not use, copy or disclose the information contained in this message or in any attachment.  Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham.

This message has been checked for viruses but the contents of an attachment
may still contain software viruses which could damage your computer system:
you are advised to perform your own checks. Email communications with the
University of Nottingham may be monitored as permitted by UK legislation.

-- 
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To post to this group, send email to e-prime at googlegroups.com.
To unsubscribe from this group, send email to e-prime+unsubscribe at googlegroups.com.
For more options, visit this group at http://groups.google.com/group/e-prime?hl=en.