switch = peripheral?

Context:


The control group performed the 50-minute task without breaks or diversions.
The "switch" group and the "no-switch" group memorized four digits prior to performing the task, and were told to respond if they saw one of the digits on the screen during the task. Only the switch group was actually presented with the digits (twice) during the 50-minute experiment. Both groups were tested on their memory of the digits at the end of the task.

More:
http://www.sciencedaily.com/releases/2011/02/110208131529.htm