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 ).
Many cognitive experiments involve asking participants to answer questions that require circular responses (Figure 1). What was the color of the shape you just saw? In which direction was the arrow pointing? How tilted was the bar? The answers required by these questions differ fundamentally from the more common, categorical responses required to questions. Was the color green or red? Was the arrow pointing left or right? Was the bar tilted more than 45 degrees from vertical, between 45-90, or more than 90 degrees?