This isn’t something specifically about MTurk, but rather about survey design itself. This study on creativity uses a method called the Alternative Uses Test, which is a valid measure used in creativity research and has been used for many years. Anyway, the study looks at different design elements:
“Using the Alternative Uses Task in an online survey, we demonstrated that scores on fluency, elaboration, and originality, core constructs of participants’ assessed creative ability, were systematically influenced by the visual design of the response boxes. The extent to which participants were susceptible to these effects varied with individual differences in trait conscientiousness, as several of these effects were seen in participants with high, but not low, conscientiousness. ”
Basically, people will have more ideas if you give them individual boxes to put their ideas in, rather than a big old text box. This makes sense given what we know about single boxes–that the bigger the single box, the more people will write.
Citation: Hofelich Mohr, A., Sell, A., & Lindsay, T. (2016). Thinking Inside the Box. Social Science Computer Review, 34(3), 347-359.