Millisecond Online Community

Dear IAT-experts,

I have an acute problem concerning the number of target and attribute stimuli for a "classical IAT" as presented on this internet page (e.g. the insect- and flower-iat):

I am currently programming an IAT with 25 names (Group A) and 25 other names (Group B) as well as 25 attributes (positive) and 25 attributes (negative) with the "standard block procedure" -

20 trials target discrimination

20 trials attribute discrimination

20 trials combined target / attribute discrimination (practice block)

40 trials critical combined target / attribute discrimination (measurement 1)

20 trials reversed target discrimination

20 trials combined reversed target / attribute discrimination (practice block)

40 trials critical combined reversed target / attribute discrimination (measurement 2)

My problem: I found out that the 50 names-stimuli are shown twice throughout the whole experiment, but that the attribute-stimuli are not - the number of trials above uses 40 attribute-stimuli because there is not a second "training block" for the attribute stimuli which would lead to an equal presentation.

Does this mean to be a problem for my experiment? Is it recommended to show both the names and the attributes stimuli equally often (by reducing the number of trials or implementing another trial)?

I have scanned through a lot of IAT-publications, but none of them made clear how they figured this problem out - could it be that it does not matter and I am just too concerned about it?

It would be great to get a response since my first volunteer participants will take place in the experiment this friday!

Thank you very much in advance,

David

Hi David,

The sequence of blocks you are using is the standard IAT sequence. There is no need to practice the attribute stimuli a second time because the association of the attribute categories with the left and right keys does not switch (whereas it does switch mid way through for the target categories).

However, because you are using 25 stimuli in each category, not all of the stimuli will appear in the practice trials. Thus, the participant will be seeing some of the words for the first time in the test blocks. That doesn't strike me as a problem if the mapping between each word and its category is obvious.

Nevertheless, if you are concerned, you could address this by creating more practice trials in the first two blocks. Specifically, you would need to run 50 target practice trials and 50 attribute practice trials to ensure that participants had practice with each item.

Hope this helps,

Sean