What is a Penile Plethysmograph?

The purpose of the Penile Plethysmograph is to collect information on what makes you become sexually aroused. It is a way to collect information just like taking a test or doing an interview. This procedure is to provide a patient and his therapist with information about what arouses. It is not to classify the patient as a homosexual, heterosexual, pedophile, rapist, or anything else.

Why is the Penile Plethysmograph useful?

Many clinicians value arousal over interest as a measure of risk. Some clients shy away from the plethysmograph because it exactly reveals the triggers for one’s sexual behavior. But, the plethysmograph is not a method for classifying one’s sexuality. It is also not part of the Deregistration initiative – meaning it is not used to “Deregister” individuals as sex offenders. It is, however a very useful diagnostic of where an individual is in their sexual response cycle. This information is useful for risk determination and treatment planning.

The Penile Plethysmograph Procedure

Of course, exact procedures may vary by clinician to a degree, but this is an account of common practices, including those at our own clinics.

How Sexual Arousal is Measured by the Penile Plethysmograph

The Plethysmograph equipment keeps track of when you are sexually aroused by continuously measuring the change in the size of your penis as you listen to different stories and see different pictures. A strain gauge will measure changes in the size of your penis. The gauge is a strip of thin metal which is curved in the shape of a “C”, and fits around your penis. The person in charge of giving the test, the Clinician, will show you the room where the test is conducted and you will place the gauge on your penis in complete privacy.

As your penis gets larger, the gauge will expand, and as your penis gets smaller, the gauge will contract. The changes in the gauge
size will send a signal to the computer to measure how much of the erection has occurred, and the computer records and prints these changes. When the session is over, the Clinician will be able to look at the printouts to see what types of stories were more arousing to you than others.

What if I am Aroused by a Stimulus that I have Never Thought of Before?

Remember that you can become aroused by a particular type of story even if you never have or ever will do anything like that story. It just means that this type of story can be arousing to you. That is important for you to know. During the session, try to sit back and relax. If you find yourself becoming aroused, just let that happen unless you are asked otherwise. If you do not become aroused, that is okay too.

Is There Anything Else Measured Other Than My Erection during the Penile Plethysmograph?

You will also have curved discs velcroed to two of your fingertips. These discs are the connectors for the galvanic skin response (GSR). When you become anxious, your skin sweats and increases your GSR. A belt will be placed across your chest to monitor your breathing. These gauges are used to monitor arousal, movement, and attempts to fake responses.

Will Someone Be Able to See Me During the Penile Plethysmograph Assessment?

No. During the session, the Clinician will be in the room next to you. During the procedure, the Clinician will monitor and control the equipment. The Clinician will make notes on your movements, comments, and other information that is important.
What Types of Stories Will Be Used?

The 22 stories you will be listening to were written and recorded specifically for the procedure. These stories have been used in many sex offender treatment programs. The stories are told by one person but are interactions the speaker is having with another person. As you are listening to each story, you should picture yourself as the person telling the story.

Imagine the things the speaker is seeing and feeling. Before each story begins, you will hear a beep. You will hear some additional beeps during the story. You will be asked to press a button each time you hear a beep. After each story, there will be a pause. Some pauses may be longer than others. The stories won’t be given in particular order. In other words, you won’t be able to tell what the next story will be based on what you just saw and heard. The Clinician may ask you to count forwards or backward during the test.

Can I Receive an Electrical Shock From the Penile Plethysmograph Equipment?

There is NO danger of receiving an electrical shock from the equipment. Safeguards are built into the equipment to prevent an electrical shock, similar to other kinds of medical equipment.

Is the Penile Plethysmograph Procedure Sanitary?

The gauges are reusable and are thoroughly disinfected after every use. When the session is over, you will be instructed to carefully remove the gauge from your penis and drape the gauge and wire over the arm of your chair. The Clinician will place the gauge in a disinfectant solution for 10 minutes as prescribed, rinse it in water, and store it away until its next use. The solution is recommended by the Centers for Disease Control and will kill any sexually transmitted disease.

Is the Equipment Sensitive?

The gauge and the recorder are very sensitive. That means they detect very small variations in the size of your penis. In fact, they will detect and record changes in your penis size even before you notice them. Your penis actually begins to get larger before you are aware of it. This equipment will detect and record even these small changes.

What if I Have to Move Around or Cough During the Penile Plethysmograph Procedure?

The equipment will also detect and record changes by the accidental movement of your body. Accidental movements are things like sneezes, coughs, deep breaths, yawns, or fidgeting in the chair. These things can cause changes in the printout. It is a good idea to tell the Clinician that you have shifted in the chair or yawned so that it can be documented.

Is There a Way to Beat the Penile Plethysmograph Test?

There are many ways that you could try to fake your responses during the test. Remember the equipment is very sensitive. Faking attempts make very distinctive lines on the printout, all of which can be identified. If you try to influence the results by faking, it will be the first thing noted in the Clinician’s report to your therapist. If you attempt to fake your responses, it can be assumed that you have something to hide. You may be required to take the test over. Think of it this way: If you have to go through something a uncomfortable as Penile Plethysmograph, you might as well be honest and get the most information from it that you can the first time.

What Should I Do Before the Test?

Please make sure that you read through all the information provided to you. Do not masturbate for 24 hours prior to taking the test. Just before coming in for the session, make sure you go to the bathroom. Additionally, the Clinician will give you a questionnaire to complete before the test is administered.

What Happens When I Come to Take the Penile Plethysmograph?

When you come in for the Penile Plethysmograph, the Clinician will go over your responses to the questionnaire. You will be asked questions to make sure you understand what is going to happen. You will be asked if you have any questions about what is going to take place during the session. You will read and sign consent forms before the Penile Plethysmograph is administered. After all of your questions have been answered and you have indicated your consent for the Penile Plethysmograph, the GSR and the Respiration Belt will be placed on you by the Clinician. You will be asked to measure your penis with a small strip of paper in private. An accurate measurement of the girth of your penis is needed.

What Happens When I go into the Room By Myself?

After going to the bathroom, you will enter the Penile Plethysmograph room. You will slide your pants and underwear down around your knees or to your ankles. Do not take your clothes off. Sit in the chair and make yourself comfortable and tell the Clinician that you are ready.

What Happens After I am Seated in the Chair?

You will be asked to sit back and relax briefly while the Clinician does the final setup of the equipment. You will be asked to put the gauge on your penis. The gauge is smaller than your penis, so you will have to very gently expand the gauge open and place it around the middle part of the shaft of your penis with the wire facing away from you. The gauge should be placed midway between the tip and the base of your penis. Be very careful when you are fitting the gauge as expanding it too much will destroy it. The gauge may feel a bit cool but it will warm up. It should fit so that it does not “clamp” onto your penis, but it should not be loose either.

When you are seated with all three gauges in place, the Clinician will make necessary adjustments before starting the test.

What Happens When the Penile Plethysmograph Procedure is Complete?

When the procedure is over, you will carefully remove the gauge from your penis and let it drape over the arm of your chair. The Clinician will then come into the room to retrieve it to disinfect it. The GSR sensor and the Respiration belt will be removed, and you can then get dressed.

The Clinician will spend a few minutes with you talking about the procedure. You will be given a list of questions to answer. When you are finished, return the answer sheet to the Clinician.

For more information about assessment, treatment and Deregistration issues call
Bruce W. Cameron M.S., LPC-S, LSOTP-S,  @ 214-431-2032