Expectancy effect

The expectancy effect (or experimenter effect) arises in science when a researcher or subject expects a given result and therefore unconsciously manipulates an experiment or misinterprets data in order to find it. The effect is so powerful that the expensive and complex double blind methodology is needed to combat it.

It is often a cause of "odd" results in many fringe experiments, notably in paranormal investigation. One example was the horse Clever Hans, who seemed to be performing arithmetic, but in reality took unconscious cues from his trainer. At another time children were given rats and told that some were bred for intelligence, some for dullness. In reality, the rats were chosen at random, but the children reported that the "smart" rats learned mazes faster.

Another example of the theory can be demonstrated in the more recent activity of music backtracking. Some people expect to hear hidden messages when reversing songs, and therefore hear the messages. To others these may sound nothing more than random sounds.

External links and references

• Skeptic's Dictionary on the Experimenter Effect
• The rat study
• An article that speaks of Expectancy effects in paranormal investigation
• Another article by Rupert Sheldrake