Why

Chapter 2. Psychology

How do people learn about causes?

In 1692, two girls in Salem, Massachusetts, started behaving strangely. Abigail Williams (age 11) and Elizabeth Parris (age 9) were suddenly overcome with fits and convulsions. With no apparent physical cause, their doctor suggested that their odd behavior might be the result of witchcraft. Soon after, several other girls were afflicted with the same condition, and more than a dozen people were accused of witchcraft.

Explanations for the resulting Salem witchcraft trials have centered on mass hysteria and fraud, but nearly 300 years later a new hypothesis emerged: ergot poisoning.¹ When ergot (a type of fungus that can grow on rye and other grains) is consumed, it can lead to ergotism, a disease with symptoms including seizures, itching, and even psychological effects. The arguments made in favor of the ergot hypothesis used weather records from the time to suggest that the conditions were right for it to grow and that the rye would have been harvested and consumed around the time of the accusations. While this seems to imply that many other people would have eaten the rye without being affected (weakening the case for this hypothesis), children are more susceptible to ergotism, making it plausible that only they would experience the ill effects. Further, another historian found correlations between areas with witchcraft trials, and rye prices and harvest times.²

Ergot seemed like a plausible explanation, but there was some ...