Randomising the Fixation duration

[David McFarlane]

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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!!

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