On tonight's episode of Law & Order: Special Victims Unit, you'll hear the SVU squad talking about a topic few people do, something called tonic immobility. It sounds complicated, but it's one of the body's most basic responses?the "freeze response"?that happens when an individual is in danger. In today's post, Dr. Rebecca Campbell, professor of community psychology at Michigan State University, discusses tonic immobility in the context of sexual assault. We invite you to watch this episode tonight at 9/8c and learn more about tonic immobility, why it happens and why it's helpful for us to talk about it.

Fight, flight, or . . . freeze? Yes. Freeze.

Many people have heard of "fight or flight," which is a way our bodies respond to very threatening, stressful situations. It's a biological response in mammals, including humans, that involves gearing up the body to either fight back against the threat or flee from the threatening situation. When the mind recognizes a situation as very threatening to the physical well-being, emotional well-being or even the very survival of the organism, the brain triggers the body to release adrenal hormones, sometimes referred to as "stress hormones." These hormones are what give the body the energy and wherewithal to fight back or get away to safety.

But sometimes, the sudden release of high levels of stress hormones triggers an entirely different reaction: freeze. When this happens, the body can't move and won't move, arms and legs don't fight back and they don't carry the body away to safety.

Why? Why would the body freeze in a threatening situation?

Good question.

Research studies with animals have documented that sometimes the best way to protect the body is to freeze, to play dead, fighting back or fleeing would only prolong the threat and endanger the body even worse (maybe even risk death). In other words, sometimes the safest solution isn't fight-or-flight. The safest option is to freeze and so the brain and body work together?to hold the organism still until the threat has passed.

So, which one? When will the body fight? Flight? Freeze?

Researchers have not yet determined why animals or humans respond with which strategy—in which situation. What is clear is that all three are normal, biological responses to threatening encounters. Researchers have determined that these responses are autonomic, which means they happen automatically without conscious thought or decision making. In other words, we don't get to pause and think about these three different options; the brain picks one quickly and goes with it. It's not something we get to decide. It's not something we get to choose. Thinking it over?weighing the pros and cons might take too long?and that could endanger the survival of the organism, so the brain is hard-wired to make a decision and go with it.

The technical term for the "freeze response" is tonic immobility (TI).

During an episode of tonic immobility, a person enters into a temporary state of paralysis. Typically, this means that the individual can't move his/her arms, legs, hands, feet, etc. The person is frozen and may appear to be dead. Tonic immobility may last for only few moments, or for several minutes, or for much longer periods of time. During the episode, the person may be aware of what's happening to them and may also understand that he/she cannot move.

Recently, researchers discovered that some rape and sexual assault victims experience tonic immobility during the attack. Tonic Immobility can happen whether the assailant is a stranger to the victim, or whether it is someone she/he knows. Victims who experience tonic immobility during the assault freeze. They can't move, they can't fight back, they can't flee. And after the trauma, a person can have difficulty remembering specific details of the event, especially when they freeze while it's happening.

It's important to remember that tonic immobility is an autonomic response, victims don't decide to do this; it's an automatic response of the brain and body, working together to try to protect the survival of the organism.

Tonic immobility can be extremely frightening and confusing to rape and sexual assault victims. Why did I freeze? Why couldn't I move? Why couldn't I scream? Why didn't I fight back? Why was I just stuck there? It's not uncommon for victims to blame themselves for this response, often because they don't understand why they did what they did. And often, not remembering the details of how things happened can bring up feelings of shame, especially when questioned by others. Most people don't know about the "freeze response." Most people don't know that research now tells us that "fight or flight" is actually "fight, flight or freeze." The freeze response, also called called tonic immobility, has been documented in many research studies with sexual assault victims. It is very real, it is very normal, it is completely biological and it is not something victims can control. Nor is their fault.

In my career as a research psychologist, I have had an opportunity to interview many rape survivors who experienced tonic immobility during the assault. None of them ever knew why they froze and because of that, they carried within them tremendous guilt and confusion. When I've told them that what they experienced sounds like tonic immobility, and when I've described to them what tonic immobility is, they are astounded. Some survivors cry in relief, some have jumped up and hugged me, some have sat there in disbelief, asking me to explain it over and over again, just to be sure. To know that this is something normal—something that happens to many survivors and it's not their fault—is incredibly freeing and healing. It can help make one part of a terrible—traumatic crime a bit more understandable.

I have also had the opportunity to talk with police officers, detectives, nurses, doctors, and rape victim advocates about these issues. Many of these professionals are not aware of "fight-flight-or-freeze" or if they are, they don't know that research now shows that some rape and sexual assault victims experience the "freeze response" during the attack. Unfortunately, there are still too many instances where our helping professionals blame victims for tonic immobility and add to victims'shame, guilt, and self-blame. However, as legal and medical system personnel learn about Tonic Immobility, they are able to help victims understand what has happened to them and help them along their journey of healing.

Dr. Rebecca Campbell is a professor of community psychology and program evaluation at Michigan State University. Her research focuses on violence against women—specifically sexual assault and how the legal, medical, and mental systems respond to the needs of rape survivors. She is the author of Emotionally Involved: The Impact of Researching Rape (2002, Routledge), which won the 2002 Distinguished Publication Award from the Association for Women in Psychology. Dr. Campbell has been active in the anti-violence social movement since 1989 and has spent 10 years working as a volunteer rape victim advocate in hospital emergency departments.

For more information on tonic immobility and the body's response to trauma, Joyful Heart recommends the following resources:

In An Unspoken Voice: How the Body Releases Trauma and Restores Goodness

By Peter Levine

Body Breath and Consciousness: A Somatic Anthology

By Ian Macnaughton

Healing from Trauma: A Survivor's Guide to Understanding Your Symptoms and Reclaiming Your Life

By Jasmin Lee Cori