When a subject came the first time for this measurement he was instructed in the following words:

"Our task now is to discover how small an electrical shock you can feel. Understand, the shocks will be very small indeed; none of them will be painful. In fact, most of them will be so small that you will have to give closest attention to feel them at all. In the beginning they will be strong enough so that you can feel them rather easily. From this strength they will be made gradually weaker and weaker. Your problem is to attend as carefully as possible and respond every time you feel a shock by pressing this button in your left hand. The shocks are produced by the action of this pendulum. You will notice that a shock comes in a particular relation to the noises which the pendulum makes. The shocks will never come at any other time but just at that position, so when you hear the 'click,' 'click' of the pendulum, as if it said 'ready, now,' then attend very carefully and respond if you feel the shock. The shocks will not always come through to your fingers; there are some blanks when no shocks are given. Of course you will be unable to tell the difference between blanks and those times the shocks are too weak to bo felt so your only problem is to give most careful attention and respond every time you believe you feel the shock. Let your hand and fingers be relaxed and as comfortable as possible. The tips of the fingers should rest lightly on the bottom of the glass vessel. You may find it best to look at the hand during the experiment".

The operator first made a rapid survey to ascertain the range of the threshold. After this he recorded the voltage of every shock and whether or not it was responded to by the subject. He also recorded the position of blanks, several of which were used with every series, and he indicated if the subject responded at such times. If the subject was right-handed, the first and second fingers of the right hand were usually employed as receptors. If there happened to be an abrasion on one of these fingers which would be immersed in the salt water, another finger was substituted.1