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masked priming experiment

jens — Sun, 14 Jan 2018 02:19:20 GMT

Hello,

I am programming a masked priming experiment in which a forward mask precedes a prime which is replaced by a target. However, so far I needed to present a blank screen (actually a rectangle shape of size = 20%,10%) to "overwrite" the mask and the prime. Otherwise letters of the mask and the prime are visible when the target appears.

/stimulusframes = [1 = fixation; 30 = mask; 59 = blank; 60 = primes; 63 = blank; 64 = targets]

This solution, however, prolongs the temporal availability of the prime and seems to reduce the masking effect of the mask. Is there any way to get rid of the blank and prevent any "shine through" of the mask and prime? At the moment all stimuli, except the blank, are text stimuli with prime being in lower case and targets being in upper case.

Best wishes Jens

RE: masked priming experiment

jens — Sun, 14 Jan 2018 02:19:20 GMT

[quote]

[b]Dave - Friday, January 12, 2018[/b]

[quote]

[b]jens - Friday, January 12, 2018[/b]

[/quote]

Overwriting any previously displayed stimuli with some kind of "blank" stimulus is the way to go (cf. the "How to erase stimuli" topic in the documentation: https://www.millisecond.com/support/docs/v4/html/howto/howtoerase.htm ).

I don't understand why you don't simply display the blank and the replacement stimulus in the same frame, though. You can display as many stimuli as you want / need in a given frame (i.e. at the same point in time), you are not limited to a single stimulus per frame:

/stimulusframes = [1 = fixation; 30 = mask; 60 = blank, primes; 64 = blank, targets]

Beyond that, if you _don't_ want an extra <shape>, simply /size <text primes> and <text targets> identically and make sure both are set to a solid /txbgcolor. One will fully overwrite the other then.

<text primes>
...
/ size = (20%, 10%)
/ txbgcolor = black
/ vjustify = center
</text>

<text targets>
...
/ size = (20%, 10%)
/ txbgcolor = black
/ vjustify = center
</text>

with

/stimulusframes = [1 = fixation; 30 = mask; 60 = primes; 64 = targets]

[/quote]

Thanks a lot. I did not know it that one can display two stimuli at the same frame. Regarding, the size of prime and target. It is an essential part of the experimental procedure that primes and targets come in different cases.

Best wishes Jens

RE: masked priming experiment

Dave — Fri, 12 Jan 2018 09:59:09 GMT

[quote]

[b]jens - Friday, January 12, 2018[/b]

[/quote]