There are lots of good reasons to rent your body to science: the advancement of knowledge, the opportunity to help future generations - oh, who are we kidding? The bottom line is that by "volunteering" to participate in medical experiments (a.k.a. being a "human guinea pig"), you can pick up some well-earned cash.

Hundreds of thousands of Americans participate in varying levels of medical research every year - it can be as simple as a questionnaire or as risky as a new drug treatment that might make your hair fall out (though you'll be warned about such unwelcome side effects). And as a side benefit, you really will be advancing medical knowledge. You altruist you.

But before we strap on the electrodes, you must acknowledge one important note: before you volunteer to participate in ANY medical study, no matter how simple, you first must consider how far you're willing to go. Some experiments are more involved, time-consuming, and (gulp!) painful than others. However, we assure you that being a human guinea pig is very safe - you won't have a mad scientist brandishing a scalpel and cackling above you. In fact, there're so many requirements and regulations that there's virtually no chance that you'll wind up disfigured, dead, or even worse, addicted to The Real World. (Or at least without your explicit permission.) For lots of information about the safety of human subject trials, visit the Office of Human Subjects Research of the National Institute of Health (NIH), and the Office for Human Research Protections of the U.S. Department of Health and Human Services.

1. LEARN ABOUT SIMPLE EXPERIMENTS

Almost every study in which you participate will have some kind of requirement. No study, after all, wants to blow its grant money on subjects who they know will not fit their needs. Some studies will only want college-educated men between the ages of 30-32, and some studies will only want Polynesian grandmothers who have had at least 10 children. The more specific the requirements are, the more likely that you'll get paid a lot of money if you fit them.

Simple experiments are, by nature, simple to conduct and to find subjects for. These usually involve doing nothing to you per se, but just studying your current state. Questionnaires, quizzes, a blood test, an MRI: these are all relatively simple. Here are the three basic categories of simple experiments:

Questionnaires and interviews
Medical exams and/or interviews: Type I
Medical exams and/or interviews: Type II

Questionnaires and interviews

These experiments are easy, quick, but also the lowest paying. Psychologists, sociologists, anthropologists, and their lackey grad students usually run them, so if you can endure these armchair social reformers without falling asleep, you'll be able to find lots of experiments. These types of studies usually involve an interview or questionnaire for you to fill out, or in some cases looking at images and describing your feelings toward them (usually through multiple choice questions).

We'll tell you upfront that these are incredibly easy and a great way to make some extra cash. This is an especially attractive option for college students, since you can just walk around campus and find out what studies are taking place.

  • What it generally pays: Between $5-$20, depending on how long it takes. If you're in college, many professors will give you extra credit in lieu of cash for helping their grad students with a particular study.

  • Possible risks: Extreme boredom, and you sometimes have to return for follow-up sessions.

Medical exams and/or interviews: Type I

Many researchers are interested in the correlation between one's general health and his/her stress levels, anger management, or other mental factors - this is where you cash in. For Type I exams, you usually are subjected to a lengthier examination that will probably involve a general physical (height, weight, blood pressure, etc.), and then answer questions about your mental health.

(By the way, if you do become a human guinea pig, you'll hear the word "correlation" a lot - if researchers don't find a "positive correlation," they'll become the money-wasting Kevin Costners of the scientific community.)

  • What it generally pays: The range is wide, but you could pocket anywhere from $20-$100.

  • Possible risks: A cold stethoscope, the revelation of private information, and time.

Medical exams and/or interviews: Type II

The same as the Type I experiments above, except these may involve some more advanced procedures such as:

  • Blood tests: Not a big deal, but if a paper cut makes you queasy, you may want to stay away from this. Wimp.

  • EKG: Those white, circular stickers on you that measure heart function and brain response. It doesn't hurt at all, and you can pretend you're a cyborg.

  • MRI: A doctor will slide you headfirst into a coffin-like tube to see what's going on inside your organs. If you're claustrophobic, avoid these - you'll freak out. But they're so expensive you probably won't encounter this in a voluntary experiment.

  • Internal exams: These can involve vaginal exams and/or rectal exams. Need we say more?

This isn't an exhaustive list, but they are the major tests that'll you encounter. Remember, the more you allow to be done to yourself, the more money you'll probably make. But if the doctor wants to remove limbs or organs, we suggest that you take pause. All the money in the world does you no good without a brain. Just ask any celebrity.

  • What it generally pays: Usually a little more than the Type I experiments. It depends on the tests given, but the range is about $50-$100.

  • Possible risks: It's very rare, but you could have some weird reaction to a test. Also, after a blood test, you may feel light-headed or queasy.