What is a Penile Plethysmograph?

Pronounced “pla-thiz-mo-graf”. The purpose of the Penile Plethysmograph (“PPG”) is to collect information on what and who you find sexually attractive. This information can then be used in a psychosexual evaluation that can help determine what kind of a risk a person accused or convicted of a sex crime might pose for the future (if any). It is also often used in treatment planning for probationers. 

How is sexual arousal measured by the penile plethysmograph?

The Plethysmograph equipment keeps track of when you are sexually aroused as you listen to different erotic stories. It continuously measures the change in the size of your penis as you listen to different stories and see different pictures. A “strain gauge” is a thin rubber ring that you will place around your penis.  The strain gauge is connected to a computer that will measure changes in the size of your penis. The person in charge of giving the test (the Clinician), will show you the room where the testing is done and you will place the gauge on your penis in complete privacy.

Once the testing commences, your penis circumference will change (call “tumescence”). 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 an erection has occurred. When the session is over, the Clinician will be able to better understand what types of stories were more arousing to you than others.

What if I am aroused to a stimulus that I have never thought of before?

You can become aroused to a particular type of story even if you never have or never will do anything like that story. It just means that this type of story can be arousing to you. During the session, try to sit back and relax. If you find yourself becoming aroused, just let that happen. If you do not become aroused, that is okay too.

Is there anything else measured other than my erection during the PPG?

You will also have a rubber belt placed across your stomach to monitor your breathing. And you will be sitting on a “pressure cushion” that will be measuring movement and tightening of your muscles.  These gauges are used to monitor arousal, movement, and attempts to fake responses.

Will someone be able to see me during the PPG 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, and make notes on your movements, comments, and other information that is important.

What types of stories will be used?

The 27 narratives you will be listening to were written and recorded specifically for the PPG. The stories are told by one person about the 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. 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 heard. 

Can I receive an electrical shock from the PPG?

There is NO danger of receiving an electrical shock from the equipment. 

Is the PPG procedure sanitary?

The PPG is an FDA-approved medical device and we follow sanitizing guidelines by the Center for Disease Control.

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 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 PPG?

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 with 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 as 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?

Do not masturbate or have sex for 24 hours prior to taking the test. Just before coming in for the session, make sure you go to the bathroom. Once the testing begins, you won’t be able to have a comfort break for 1.5 hours. Tell the clinician any medications you have taken during the past 24 hours. The Clinician will give you a questionnaire to complete before the test is administered. Please make sure that you read through all the information provided to you. 

What happens when I come to take the PPG?

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. 

What happens when I go into the room by myself?

After all of your questions have been answered, you have indicated your consent for the Penile Plethysmograph, and after going to the bathroom one last time; you will enter the testing room. The Respiration Belt will be placed on you by the Clinician. After she leaves the room, you will slide your pants and underwear down around your knees or to your ankles. Do not take your clothes off. You will be given a hand towel to cover your genitals. Then you will 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 set up of the equipment. You will be asked to put the gauge on your penis in privacy. 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 break 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 the gauge in place, the Clinician will make necessary adjustments before starting the test.

What happens when the 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 and remove the Respiration belt, and you can then get dressed. The Clinician will spend a few minutes with you talking about the procedure.