The expt element defines the sequence in which blocks are run. For our picture IAT, the expt element is defined as follows:
<expt> / blocks = [1=attributepractice; 2=block2; 3=block3; 4=block4; 5=block5; 6=block6; 7=block7; 8=block8; 9=block9] / postinstructions = (summary) </expt>
The expt element is pretty simple. The blocks attribute specifies a sequence of 9 blocks. The first block is "attributepractice" block in which subjects practice classifying the good and bad word stimuli. Blocks 2 through 9 are set to between-subject variables named "block2", "block3", "block4", "block5", etc. When the script is run, these variables will be set to the names of real blocks depending on the subject number that is assigned. By using between-subject variables, the script counterbalances the order in which the test blocks are run across subjects so that half our subjects run the compatible pairing first, and the other half runs the incompatible pairing.
The between-subject variables are defined as follows:
<variables> / group = (1 of 2) (block2=targetcompatiblepractice; block3=compatiblepractice; block4=compatibletestinstructions; block5=compatibletest; block6=targetincompatiblepractice; block7=incompatiblepractice; block8=incompatibletestinstructions; block9=incompatibletest] / group = (2 of 2) (block2=targetincompatiblepractice; block3=incompatiblepractice; block4=incompatibletestinstructions; block5=incompatibletest; block6=targetcompatiblepractice; block7=compatiblepractice; block8=compatibletestinstructions; block9=compatibletest] </variables>
The variables element defines between-subject variables based on the subject number that was entered when the experiment is run. The first group attribute specifies the variable values for odd numbered subjects (i.e., the first of every two subjects). For odd-numbered subjects, block2 is targetcompatiblepractice, block3 is compatiblepractice, block4 is compatibletestinstructions, and so on. Thus, odd numbered subjects perform classifications with the compatible pairing first. For even-numbered subjects, the incompatible pairing comes first.
By default, Inquisit will save a lot of data to the data file, much of which isn't relevant to the IAT. Although there's not much harm in having this data around, we can save ourselves some time and disk space by telling Inquisit to save just the data we care about. We do this in the data element as follows:
<data> / columns = (date time subject blockcode blocknum trialcode trialnum response correct latency stimulusnumber1 stimulusitem1 stimulusnumber2 stimulusitem2) </data>
The columns attribute lists the data columns to save. All other data columns will not be saved.
Finally, we'll specify some default settings that apply to this script using the defaults element.
<defaults> / screencolor = (0,0,0) / txbgcolor = (0,0,0) / txcolor = (255, 255, 255) / fontstyle = ("Arial", 5%) </defaults>
The screencolor attribute sets the color of the screen throughout the experiment to black. The txcolor and txbgcolor attributes specify the foreground and background colors for text stimuli as white text on a black background. The fontstyle attribute specifies that all text elements should be presented in Arial font at 5% of the screen height unless otherwise specified.
Our Picture IAT is now complete. You can run the experiment by selecting the "Run" command on the "Experiment" menu.
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