The next higher level of knowledge is “know-how” – i.e., knowing how to decide on an appropriate response to a stimulus. Such knowledge is required when the simple programmable relationships between stimuli and responses, which are the essence of “know-what” knowledge, are inadequate. This might be the case, for instance, when there is considerable “noise” in symp-tomatic information so that the direct link between symptoms and a medical diagnosis is uncer-tain. “Know how”-type knowledge permits a professional to determine which treatment or action is best, even in the presence of significant noise.