A spate of arsons is rocking Los Angeles this week. More than fifty cars have been set on fire over the last three days. Authorities have detained a man identified as a “person of interest” in the case, but so far very little other information is available. What drives a person to set fires?

A 1994 study of 153 adult arsonists provides some insight. Some arsonists have obvious financial motives, but for many the urge to set fires is psychological. The survey found that most of the arsonists suffered from a mental illness, and many were mentally handicapped or had a history of special education (a finding noted in other studies as well). The most common motive cited was “revenge,” but even that factor was cited by only a third of the subjects surveyed. Still other experts cite misplaced sexual desire, a fascination with fire or control, or sadism, but each of these theories has detractors. That means authorities probably won’t be able to guess a motive until they can interview a suspect—the sooner, the better.