Many experiments require counterbalancing sequences of trials. For example, I’m currently running an experiment on serial dependence1. In my experiment, participants report the orientation of a grating2 stimulus on each trial. The serial dependence effect is how their responses on one trial depend on either the orientation of the previous trial or their response on that trial. To tease apart the effects of prior stimuli from prior responses, I’m manipulating the visual contrast of the gratings ( Michelson contrast ).
It may be the case that Amazon Mechanical Turk WorkerIDs are not anonymous. Lease et al., 2013 describe at length how personally identifying information may be exposed when a researcher shares WorkerIDs. It is unclear to me the extent to which Amazon constructs their WorkerIDs at present, given that one of their striking demonstrations did not apply to my WorkerID. That is, they describe simply googling the WorkerID and receiving a picture of the participant, along with their full name.