Unfortunately, naive explanations of behavior are usually ambiguous and often contradictory. But one should realize that there is often a considerable difference between the common-sense analysis of behavior and the scientific one. Aristotle reached the very sensible conclusion that a heavy object falls to the ground faster than a lighter one. He dropped objects of different weights and made precise observa tions of the time each one took to reach the ground. At any time during that 2000 years someone could have performed a similar experiment and discovered that weight has no effect on the rate of fall.
Introspective data are useful as long as one takes into consideration their limitations.
Information obtained from this type of investigation is called introspective data. No one can be sure that one person's inner perceptions are the same as another's, even though they may go by the same name. If we want to build a science of psychology only for Joe Smith, we want to know as much as possible about Joe Smith's inner states. But if we want to build a science which has some validity for everyone, we must seek evidence that is far more objective and public. We often hear references to inner perceptions advanced as evidence in support of an assertion.