forecastingprinciples.com Reviews of Important Papers on Forecasting,
1985-1995 Reviews
Review of:

Blackmore, Susan and Tom Troscianko (1985), "Belief in the paranormal: Probability judgments, illusory control, and the 'chance baseline shift,'" British Journal of Psychology, 76, 459-468.


[Review written with J. Scott Armstrong]

A belief in paranormal effects is widespread. One study found that over half of a sample of students believed they do exist. Many of the believers are convinced that they have experienced it. This study explores two reasons for the belief in paranormal effects (psi). One is that psi actually exists. The other is that believers rnisperceive normal events as evidence of psi. Blackrnore and Troscianko conducted three experiments to compare believers (sheep) with non-believers (goats). Sheep performed poorer on tasks involving probabilities (e.g., "How many people do you need to have at a party to have a 50-50 chance that two of them will have the same birthday (not counting year)?" Subjects were to chose from three answers: 22, 43 or 98. Sheep also exhibited a stronger illusion of control over events (coin tossing). An important finding was that sheep tended to underestimate base rates; thus, events seemed more surprising to them. Finally, the researchers found no evidence that any of the subjects possessed paranormal powers.

[Conclusion by JSA: Forecasts by those who claim to have paranormal powers have no added value.]