On a $400,000 loan, for example, a buyer who made only minimum payments over the first five years would add more than $27,000 to the end of the loan, assuming short-term rates increase by one percentage point over the course of the loan, said Robert Binette, a mortgage broker with Hamilton Mortgage in Ridgefield, Conn. The monthly payment would jump from $1,718 in the final month of the fifth year to $2,580 after the loan was reset, a difference of more than 50 percent.

In other words, most investors tend to ignore events that are scheduled to happen more than five years into the future. They are like drivers who ignore warning signs about slippery pavement just around the bend, and instead wait until nearly the last second to apply the brakes.

Quite distinct from the oral damage done by other drugs, sugar and smoking, methamphetamine seems to be taking a unique, and horrific, toll inside its users' mouths. In short stretches of time, sometimes just months, a perfectly healthy set of teeth can turn a grayish-brown, twist and begin to fall out, and take on a peculiar texture less like that of hard enamel and more like that of a piece of ripened fruit.

All the researchers cautioned that any of these wired behaviors set by master genes will probably be modified by experience. Though male fruit flies are programmed to pursue females, Dr. Dickson said, those that are frequently rejected over time become less aggressive in their mating behavior.