I am working on a project using the dot probe paradigm (i.e., participants see a threat and non-threat stimuli and then they need to press a key that appears on a certain side of the screen which is either an E or F). The task consists of 200 trials with 4 blocks in total meaning there is a total of 800 trials. Unfortunately, this would take about 100 minutes and in addition there is about 40 minutes of filling in questionnaires.
Is anyone aware if participant motivation or focus greatly drops after a certain time of testing, whether from personal experience or research on this question?
Actually, in cognitive psychology long experiments (even of 3 hours or more) are very common.
I think the most important question is whether you think motivation and focus are important for the process you're interested in. In fact, the effects may even be stronger when participants become tired and react more on their impulses. I would recommend building in some breaks in between the blocks, though.
I would concur with Anouk van der Weiden. If tiredness and drop in motivation does influence your results in an unwanted way, I would try and break the sessions in smaller units, so that participants can take adequate breaks.
Or, if you can, let them know in advance about the time they need to spend there, so that they can prepare. Still, I do believe that concentration drops after about 30 minutes or so, especially if the blocks are very similar to each other.
It all depend how how interesting the task is--long questionnaires may not be taken too seriously-
You could break your current test into two halves and do a small split-half reliability study to see if there is deviation between the first half (50 minutes) and second half of the test as is. If you find deviation, you may considering shortening the task.
Thanks for the suggestions everyone. Splitting the test into half and doing a split-half reliability test is a good way I think to find out if spending more time on the task affects the results.
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