The Test goes like this:
1. Select a variable you think the person might be maintaining at some level. In other words, guess at an input quantity.
2. Predict what will happen if the person is not maintaining the variable at a preferred level.
3. Apply various amounts and directions of disturbance directly to the variable.
4. Measure the actual effects of the disturbances.
5. If the effects are what you predicted under the assumption that the person is not acting to control the variable, stop here. The person is indeed not acting to control it; you guessed wrong about the variable.
6. If an actual effect is markedly smaller than the predicted effect, look for what the person might be doing to oppose the disturbance. Look for a cause of the opposition to the disturbance which, by its own varying, can counterbalance variations in the input quantity. That cause may be caused by the person's output. You may have found the feedback function.
7. Look for the way the person can sense the variable. If you can find no way the person could sense the variable, the input quantity, stop. People cannot control what they cannot sense.
8. If you find a means of sensing, block it so that the person cannot now sense the variable. If the disturbance continues to be opposed, you have not found the right sensor. If you cannot find a sensor, stop. Make another guess at an input quantity.
9. If all of the above steps are passed, you have found the input quantity, the variable the person is controlling. Read more »
