DUAL task experiment

[Francisco José Tornay]

Hello Zainab,

I'm not completely sure whether I got you right. If not, please correct me.

In my opinion there is only a little problem.

In the case where the SOA is longer than stim1 duration there is no problem.
In the other case (SOA < stim1) there is only a difference: the fappearance
of stim2 should not delete stim1 but it should wait for a period (which
equals stim1 - SOA) and only then delete stim1.
There are several possibilities: a simple one would be to use two different
procedures: one for trials on which SOA > stim1, the other for trials on
which SOA < stim1. The first one is clear enough.

Procedure for SOA < stim1. It is a copy of the other procedure except for
the following:

1) Stimulus 1 appears for an interval equals to SOA (whether fixed or
varied by an attribute)
2) Stimulus 2 appears without deleting stimulus 1 (set background property
to "transparent" and make 	sure both stimuli do not overlap, change the X
and Y properties). This object (textdisplay or 	whatever) would remain for
a period equal to SOA minus stim1 duration).
3) Stimulus 2 remains on screen while stimulus 1 disappears
	You can do this by presenting a new object, which would again present
stim2  but deleting 	the previous display (it would be a copy of the
previous object but with the background 	property set to "opaque"). This
would last for a period equal to stim2 duration minus SOA.

You may need to set up new attributes for the durations of the three above
mentioned objects (if they are variable).

I am not sure whether this has solved your problem and whether I made
myself clear. In case you have any doubt or problem, feel free to write again.

If you don't like the idea of using two separate procedures, it would not
be difficult to merge them into a single one by increasing the number of
the attributes.


Hope this helps,

		Francisco Tornay