Attitude changes in those who receive messages can be affected by the conditions of explicitness and effort under which the messages are transmitted. Messages produced under conditions of "publicness" will change more attitudes among receivers than those produced under more private conditions. Likewise, subjects who receive messages under a condition of high effort will change their attitudes more readily than those operating under a condition of low effort. If the two factors of explicitness and effort are additive in producing commitment, then messages produced under conditions of both "publicness" and high effort will result in the greatest amount of attitude change. Results of a study supported these hypotheses, although they did not support the theory that messages received under both conditions of "privateness" and low effort resulted in attitude changes that were significantly different from those in the two groups, "high effort-privateness" or "low effort-publicness." (RN)