At a convention of biological scientists one researcher remarks to another, "Did you know that in our lab we have switched from mice to lawyers for our experiments?"

"Really?" the other replied, "Why did you switch?"

"Well, for three reasons. First we found that lawyers are far more plentiful, second, the lab assistants don't get so attached to them, and thirdly there are some things even a rat won't do. However, sometimes it very hard to exterpolate our test results to human beings."