Episode 3

Episode 3


So far we have learned how to present stimulus, but usually we want our participants to be active in the experiment. 
Let's learn how to do this.


We try to create script in which participants schould press spacebar each time when they see B letter.


In this episode we discuss letter's (stimulus) presentation and in episode 4 we add some interaction.

Below, you can find simple script presenting A and B letters, press "run the script" green button above to see how it works, 
and then we go through them to figure out how it works.

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First, we creat two text's elements: text element called A and text element called B, which are our sitimulus, 
in addition we define stimulus fonts types: size and colour, using fontstyle attribute.
(Tips: you can learn more about elements by clicking on them and pressing F1)
<text A>
/ items = ("A")
/ fontstyle = ("Arial", 10%, true)
/ txcolor = (255, 0, 255)
</text>

<text B>
/ items = ("B")
/ fontstyle = ("Arial", 10%, true)
/ txcolor = (55, 100, 255)
</text>
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Second, by trial elements we organize how to present our A nad B stimulus.

<trial show_text_A>
/stimulustimes = [0=A]
/timeout = 550
/posttrialpause = 100
</trial>

<trial show_text_b>
/stimulustimes = [0=B]
/timeout = 550
/posttrialpause = 100
</trial>

Try to figure out how post-trial pause attribute works, press F1 and find a decription.

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Next, we organize previously defined trials in blocks using block elements.

<block block_all_a>
/trials = [1-5=show_text_b]
</block>

<block block_A_and_B>
/trials = [1-5=noreplace(show_text_b,show_text_A)]
</block>


block_all_a presents only trial show_text_b, and does this 5 times.

block_A_and_B as well presents 5 trials BUT shows trial show_text_b OR trial show_text_A.

We use noreplace () function to handle random selection of trials. 
Noreplace () function randomly selects without replacement from a set of values placed in brackets.
This means that every time block_A_and_B starts one of its 5 trials, the trial will be randomly chosen from a set of two trials (show_text_b,show_text_A).
Additionally, noreplace selects without replacement, so e.g. after choosing show_text_b, only show_text_A left in a set, so it will be next.


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Finally, we link blocks of trials in one experimental procedure using expt element.

<expt >
/blocks = [1=block_all_a;2=block_A_and_B]
</expt>


In this script you can see how simple sequence of stimuli presentation in Inquisit can be organized.
This structure is quite universal and you will use it almost all the time when creating scripts.

As you probably have noticed, we have: text, trials, blocks and expt elements - using these elements you can create your own script.

text element 
The text element defines a set of text stimuli and determines how items are selected and displayed on the screen.

trial element
The trial element controls the timing and the content of stimulus presentation. 

block element
The block element defines a sequence of trials and instruction pages to be run.

expt element 
The expt element defines a sequence of blocks and instruction pages to be run. 


This script is quite boring, let's go to episode 4 to add some interaction!