Most investigations of attitude change have dealt with the effects of some experimental manipulation on a given dependent variable. Studies on the elects on a persuasive communication are not usually concerned with the amount of change produced by the communication itself; instead, they may examine the relative effectiveness of, say, attributing the message to a high as opposed to a low prestige communicator. Similarly, studies dealing with the effects of active participation are usually not concerned with the amount of change produced by the participation experience, but rather with the relative effectiveness of, for example, paying the person different amounts of money for his participation, over the years, a large number of such variables have been manipulated in attempts to identify the most effective means of producing change. Almost without exception, these variables have not been found to have a systematic effect on the amount of change produced. In the following discussion we shall outline some basic principles of change that may help to explain these inconsistent findings