I have a question about calculation of response bias for a old/new recognition memory task I've done. In this task participants memorized 12 red shapes and 12 blue shapes first. Then, in the next phase of the task, they were presented with those 24 items and 24 new items and responded whether they were old or new. Importantly, all the shapes in the recognition phase were black colour. I'm investigating whether the recognition accuracy differ for red and blue items at encoding stage, but I have a problem with calculating false alarm and response bias. Since there was no colour distinction at recognition stage I cannot calculate false alarm separately for the red and blue items.
Is there any way to correct response bias for this task?
Thank you.