The subject will receive two asynchronous stimuli - one to each finger - in rapid succession. Determine which of the stimuli came first, and click on the corresponding box on the computer screen*.
Some people find it easier to remember which vibration came last, and then select the opposite side. The strategy you choose does not impact the efficacy of the test. Response time is not important for this test. If you cannot determine which stimulus came first, make the best guess possible.