There are two different aspects to a reminder: the signal and the message. Just as in doing an action we can distinguish between knowing what can be done and knowing how to do it, in reminding we must distinguish between the signal-knowing that something is to be remembered, and the message-remembering the information itself. Most popular reminding methods typically provide only one or the other of these two critical aspects. The famous "tie a string around your finger" reminder provides only the signal. It gives no hint of what is to be remembered. Writing a note to yourself provides only the message; it doesn't remind you ever to look at it. The ideal reminder has to have both components: the signal that something is to be remembered, and then the message of what it is.
( Donald A. Norman )
[ The Design of Everyday Things ]
www.QuoteSweet.com