Creating Blocks

The next step is to define the different kinds of blocks that will be used in the experiment. For this experiment, two block elements will be defined, one for practice trials and the other for data collection.

First, let's define the practice block element. 

<block practice>
/ bgstim = (pleasantreminder, unpleasantreminder)
/ preinstructions = (intro1, intro2, intro3)
/ trials = [1-40 = noreplace(pp, pu, up, uu)]
/ errormessage = (errormessage, 200)
/ blockfeedback = (latency, correct)
</block>

The block is called "practice".

The bgstim attribute tells Inquisit to keep the pleasantreminder and unpleasantreminder on the screen during the block. Remember these stimulus elements were defined previously, we wanted to keep "a=unpleasant" and "5=pleasant" on the screen during the trials in the upper left and right quadrants respectively.

The preinstructions attribute refers lists some of the instructions pages created in the previous section. This command tells Inquisit to display the pages named intro1, intro2, and intro3 at the beginning of the block.

The trials attribute defines trials (40) for this practice block that are randomly without replacement selected from the four trial types: pp, pu, up, uu. This guarantees that each trial type will be presented 10 times.

The errormessage attribute indicates that when the participant responds incorrectly in this practice block, the errormessage text stimulus (previously defined) will be displayed for 200 ms. Giving feedback during a practice trial is a good idea because you generally want the participant to learn the right way to perform their task. As you'll see, we remove this feedback in the data collection blocks.

The blockfeedback attribute specifies that after the block is over, subjects will be shown their mean latency and percent correct.

Now, lets define a data collection block. 

<block data>
/ screencolor = (175, 175, 255)
/ bgstim = (pleasantreminder, unpleasantreminder)
/ preinstructions = (ready)
/ trials = [1-40 = random(pp, pu, up, uu)]
/ blockfeedback = (latency, correct)
</block>

This element is just like the practice element except that the participant is no longer given the feedback because we removed the errormessage attribute. Also, the block begins with a different instruction page called "ready".

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