That’s part of the very clever title of a new paper, “Turking Overtime: How Participant Characteristics and Behavior Vary Over Time and Day on Amazon Mechanical Turk” available here: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2836946.
“We find no time or day differences in behavior, but do find that participants at nights and on weekends are less experienced with online studies; on weekends are less reflective and worse at comprehension questions; and at night are less conscientious and more neurotic. These results are largely robust to finer grained measures of time and day. We also find that those who participated early on in the course of the study are more experienced, comprehending, reflective, and agreeable, but less charitable, than later participants.”
Interesting stuff–especially if you want to get more ‘naive’ workers. Nights might be better.