RE: Random red dot, to measure participants attention level?

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RE: Random red dot, to measure participants attention level?

Random red dot, to measure participants attention level?

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SpoHo	SpoHo posted 11 Years Ago Topic Details Share Topic
Group: Forum Members Posts: 27, Visits: 115	Hi! At the beginning of our Experiment, we present 18 images (7.5 seconds each). To keep the participant interested, we want to give him a little extra task, like counting random red dots. So here's what we came up with: On random images, a red dot should appear in a random position on the screen. The task would be to count the number of red dots being shown during the presentation. So here are my questions: How can I show a red dot, in a random position? How can I count, how many times the red dot appeared, so I can give the participant a feedback wether he was right or wrong? (custom value++)? thanks a lot!! best regards, Manu
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Dave	Dave posted 11 Years Ago ANSWER Post Details Share Post
Group: Administrators Posts: 13K, Visits: 108K	#1: You display the dot-stimulus just like any other stimulus. Via a <trial>'s /stimulustimes or -frames. Alternatively you can 'inject' the dot-stimulus using the <trial> element's insertstimulustime(), etc. functions, details for which can be found in the language reference for the <trial> element. #2: /position attributes etc. accept expressions and the like. You can easily randomize a stimulus' onscreen position using <values>, <expressions>, <list>s and/or a bit of /ontrialbegin logic. Which approach turns out to be the most suitable depends on what exactly you want to achieve. A forum search will provide you with numerous examples regarding position randomization. #3: Whether you need <values> to count dot-instances depends on how you decide to implement them in the first place. But, in general, yes -- using values is a good idea and provides a lot of flexibility.
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