positioning variables in specific locations in E-prime

[amelia...@gmail.com]

Hello,

I need help finding specific resources that will help with coding my experiment. In general, I think the experiment is relatively simple (I'm a beginner at this).

1. I need to display a single two-digit  number on a single trial that is at one of four specific distances from the left side of the screen (and in the center of the screen - meaning only the x coordinate will change). On number will be shown on a single trial and will be randomly drawn from 10 to 99. The number displayed on each trial will change. Where can I find specific location about XY coordinates in E-prime so that I can control where the number will be displayed? 

I created a list that has the random number for each trial (var 1) and the specific locations (var 2) that a given number should be displayed on a single trial. So far, I can get the number to display using the InLine coding, but it's always in the center of the screen. How can I display each at a specific x coordinate? I haven't found any useful examples or descriptions of this.

Thanks for the help.

[David McFarlane]

You want to use a Slide object. Slide sub-objects (e.g., SlideText)
placed on a Slide have properties for X and Y position (look at the
Frame tab of the properties pages), and these accept attribute
references from a List or inline code.

-- David McFarlane

[Amelia C . Warden]

Thank you, David McFarlane! This worked for that part of the task. I also realized that I probably do not even need to use the InLine code to do this given that I can set the Slide to have specific X and Y positions based on a List variable (which I can randomize). 

There is another part of this task that requires there to be an object (such as a fixation cross) that always appears at the same location on the left side of the screen throughout the task. Do you have a reference example for how to make this object occasionally jitter or rotate or flash on/off (something to indicate that it moved)? Or, will something like this require hard coding an object using the InLine feature so that it will randomly move on some trials but not others (akin to a continuous monitoring task)? 

Thank you again! Sincerely, Amelia 

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Amelia C . Warden

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[David McFarlane]

Amelia,

I might need more details on what you want here. Do you want the
fixation cross to jitter from one trial to another, but remain in a
fixed location during each trial? Or change position during different
specific phases of a trial, in time with other things that happen? Or
do you mean for the fixation to change position according to some
schedule during a trial? Some of these scenarios are easy, others are
harder. Perhaps you could begin with an explicit outline of a trial.

-- David McFarlane

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[Amelia C . Warden]

Hi Dr. McFarlane, 

The original goal is to have the fixation cross continuously displayed at the same time that a number appears in one of four horizontal locations (y=center of the screen). I think based on your questions I want: the fixation cross to sometimes jitter 1 or 2x OR not at all during a single trial before the 2-digit number appears. Currently, I have the task spread out across several slides to do this - so it visually does what I want but I think that some issues (collecting responses) may arise given that I have used so many slides. Below is (hopefully) a better description and a mock up of what I'd like a single trial to look like. 

During a single trial, the red fixation cross may jitter (slight movement back and forth) one or two times or not at all. This continuous monitoring task is to ensure that they maintain fixation at the left side of the screen because I want to get a measure of scan time from the fixation to the number when it appears on the display some degrees of separation from the fixation.

 

During the same trial a number will appear at 1 of 4 horizontal locations from the left side of the screen. This was accomplished by setting the x-position of the random number variable in the List to one of four predefined locations.

 

Currently, I have four separate slides with a fixation cross. The x-position of the fixation cross on each slide is linked to one of two list variables to either make it move to the right then back to the left or stay in the same place. Each of these four Slides lasts 1 s, then a slide with the cross and random number appears for 1 s, followed by a response Slide that is infinite until they enter the 2-digit number. The slides with the fixation cross accept ‘spacebar’ as a response because people are supposed to hit the spacebar if they see the cross move. I am currently considering each trial lasting a total of 3 seconds (it is currently not at 3 s because it’s distributed across several slides). 

 

I feel like having so many slides may cause an issue with collecting the data. I need to record any time that they hit ‘spacebar’ when they see the fixation cross move AND the time that they enter the first digit of the 2-digit number. Maybe this can be accomplished with multiple slides. Do you think it can be done on a single slide? 

Thank you again for your time and the great work you put into this forum.

Sincerely, 

Amelia

To view this discussion on the web visit https://groups.google.com/d/msgid/e-prime/1a62b54b-0c2b-1e27-cbd9-476635133ba3%40msu.edu.

[David McFarlane]

Amelia,

Your manner of presentation using multiple Slides looks sound to me, I
would probably do something like that myself.

What remains is the matter of collecting responses. You want one RT
from the onset of the trial to the press of the space bar when the
subject notices the fixation cross move, and another RT for when the
subject enters the first digit of the stimulus (RT from the onset of the
digit stimulus or from the start of the trial?).

Instead of collecting a response to each one of the intervening fixation
cross displays, you should use Extended Input -- see the tutorial for
this in the E-Prime Users Guide (the NestingXRT example). So you would
set up an input mask in the first fixation cross with a Time Limit that
extends across all of the fixation crosses, and that will take care of
that. Or, if it makes more sense, use a Wait object with Duration 0 at
the start of the trial and use that for the Extended Input across the
following fixation crosses.

If you want the RT for the digit stimulus from the onset of the stimulus
then that makes things easier, otherwise you might want to use a Wait
object with Extended Input as just described. Note that if you use an
increased MaxCount and/or a Termination Response to collect a 2 digit
response then the RT will reflect the *final* entry, not the first
digit. In that case, to get at the data from the first digit you would
have to delve into some tricky inline code, see the Multiple Response
Collection example that you may download from the PST website.

Finally, if you want the total time of each trial to stay consistent
while ignoring timing discrepancies from individual objects, use
Cumulative timing mode instead of Event timing mode. For more details
on this, see the Critical Timing section of the Users Guide (or take my
online course!). (In more intricate cases I use SetNextTargetOnsetTime
in inline code to realign objects to some timing standard -- for more
info on that, see that topic in the E-Basic Help facility, or search
this Group for discussions of SetNextTargetOnsetTime.)

-- David McFarlane (btw, thanks for the honorific, but no Ph.D. here,
merely an M.S. in Biophysics & Theoretical Biology)

> Amelia C . Warden