Psi missing is one of the most startling discoveries of modern parapsychology. At times, certain individuals persist in giving the wrong answers in psi tests. The accumulation of systematically wrong answers can be so flagrant that it suggests something quite different than a mere lack of psi abilities: it is as if people use psi to consistently avoid the target, unconsciously "sabotaging" their own results!

A number of different psychodynamics could conceivably lead to psi missing, but one of the most solidly established is quite simple: belief. In 1942, Gertrude Schmeidler, professor of psychology at City University of New York, set up a questionnaire to explore students' beliefs about psi. She used the term "sheep"  to refer to those who were confident about the reality of psi and "goats" for those who doubted its existence or its pertinence in the context of the test. After the questionnaire, she gave the students a classic psi test with ESP cards in which they tried to guess sequences of target- cards. Then Schmeidler compared the results of the psi test and those of the questionnaire. The remarkable conclusion was that the "sheep" had a significant deviation above chance, while "goats" were significantly below it.

This difference between believers and disbelievers, known as the "sheep-goat effect," has been confirmed by many other researchers. A meta-analysis by Lawrence (1992), covering 73 experiments by 37 different researchers, clearly confirms that subjects who believe in psi obtain, on the average, higher results than those who do not believe in it.

We all tend to select information which confirms our beliefs and avoid that which seems not to fit with them. Selective perception undoubtedly plays a role in our interpretation of apparently paranormal experiences. Skeptics are justified in stating that those who believe firmly in psi will tend to see its occurrence everywhere, even to the point of confusing their own interpretations with the actual events. On the other hand, disbelievers will also tend toward the complementary fallacy, always finding some so-called "rational" explanation for a psi experience, even when it happens to them. But the sheep-goat effect suggests that the differences run deeper than mere interpretation: one's attitudes toward psi affects the likelihood that such phenomena will occur in the first place. The more an individual harbors a reductionistic view of the world, the less chance such phenomena will emerge (let alone be witnessed by them); the more one is interested in interconnectedness, and open to psi experiences, the more likely the world will "respond" by creating such experiences.