Science Fact: Who has not wanted to be invisible, at least some time in their life? To be the fly on the wall observing some private moment. Gracefully avoiding an embarrassing situation. To experience the power of seeing without being seen. Or perhaps, to plunder Fort Knox?
If the meaning of life is for wishes to come true, being invisible is a wish to think about!
The Invisible Cat and the Invisible Fish
Some would put the power to be invisible on their short list of three wishes to ask of the Aladdin’s lamp genie. That might not be such a good idea. More than a hundred years ago, H. G. Welles wrote The Invisible Man. His book showed that being invisible brings with it some serious drawbacks. Nevertheless, modern writers have allowed their characters to become invisible whenever it suited their story line. Consider these examples:
– Gollum’s ring in The Hobbit.
– The Harry Potter Cloak of Invisibility.
– And the magic helmet (Tarnhelm) in Das Rheingold.
There are in fact scientists working to make people and human-scale objects invisible. Some of the newest work in China uses nothing more complicated than mirrors and glass prisms.
The Chinese illusion has very limited application. It only works in four or six directions, so that if you shift your position slightly the object is no longer invisible. Nevertheless, it is noteworthy that the researchers have managed to disappear and then reappear two living animals: a fish and a cat.
This blog post is not about how you can become completely invisible. Science is far from achieving that at this time. What science can now offer is how to make you feel invisible.
After we discuss the work, we’ll talk about its amazing potential applications. These range from help to amputees to the treatment of anxiety disorders, gender reassignment and long-distance intimacy.
The Rubber Hand Illusion
A noteworthy step toward feeling invisible was the rubber hand illusion. This phenomenon is the 1998 invention of Botvinick and Cohen, two psychologists at Carnegie Mellon University.
Here’s how we might duplicate their experiment today: Our volunteer, call him Victor, sits with his left arm resting on a table. On the table we put an upright screen large enough to hide Victor’s arm from his view. In front of him we put a life-sized rubber model of a left hand and arm.
Experimenter George sits across the table from Victor. George holds two small paintbrushes, one in each of his hands. He asks Victor to keep his eyes on the rubber hand while George uses the brushes to stroke both the rubber hand and Victor’s real hand. George strokes both hands at the same time, at corresponding positions on each hand.
How the Volunteers Reacted
In the CMU study, after ten minutes each volunteer completed a questionnaire. First, it asked for an open-ended description of their experience. Then the questionnaire asked them to agree or disagree with nine statements. Every one of ten test subjects agreed moderately or strongly with three of the statements:
– It seemed as if I were feeling the touch of the paintbrush in the location where I saw the rubber hand touched.
– It seemed as though the touch I felt was caused by the paintbrush touching the rubber hand.
– I felt as if the rubber hand were my hand.
More than half the volunteers also felt that the rubber hand began to resemble their own real hand, in terms of “shape, skin tone, freckles or some other visual feature.” Eight of the ten spontaneously expressed a feeling of “ownership.” They said things like “I found myself looking at the dummy hand thinking it was actually my own.”
To make the illusion work, the brush touches need to be synchronized in time and place. In addition, the rubber hand must be placed in a believable position relative to the volunteer’s body, that is, a position that his own hand might occupy.
The Out of Body “Body Swap” Experience
Neuroscience professor Henrik Ehrsson of the Karolinska Institute in Stockholm and his group have been studying how we sense and feel ownership of our own bodies.
Ehrsson’s group was able to extend the rubber hand illusion to the entire body with a clever experimental design using virtual reality (VR) goggles. The researchers made volunteers feel that they were outside their own body, or even housed in someone else’s body. This is the psychological version of the currently-impossible Head Transplant in an earlier blog.
How To Feel A Body Swap
Based on the earlier “rubber hand” work, the researchers believed that two elements would be essential for creating a strong illusion. The illusion required synchronous touch; and giving the subject a viewpoint that reinforced the illusion.
So they took a life-size male mannequin and mounted a pair of video cameras on its forehead, pointed down to view the mannequin’s body. The two video streams fed VR goggles worn by a volunteer, who tilted his head down toward his own body.
You can probably anticipate what came next. The researcher used two paintbrushes and simultaneously touched both the volunteer and the mannequin, in corresponding places: abdomen, lower arm, or lower leg and foot. Almost at once, the test subject felt that he was inhabiting the mannequin’s body.
The illusion worked just as well when another person took the place of the mannequin. The volunteer felt that he was that other person. Gender didn’t seem to matter! A male test subject had no trouble feeling housed in the body of a female scientist wearing the video cameras. In fact, the illusion persisted even when the volunteer, housed in the scientist’s body, shook hands with his own physical body!
However, the person or object that you are transferring your “ownership” to needs to resemble a person. It can be a human being, or a full-size mannequin, or even a miniature doll. The illusion is much weaker or nonexistent when the object is a box, chair or table.
You Can Feel Invisible
It’s amazing how easily our minds sluff off a lifetime of body awareness. We can readily believe that we are somewhere else, and someone else! So perhaps it’s not surprising that we can also believe that we are completely invisible.
The Ehrsson group decided to repeat the mannequin experiment without the presence of a mannequin. The video camera would be looking at a body-shaped region of empty space rather than viewing the mannequin’s body.
Conducting such an experiment is not as easy as it sounds. The lead investigator, Arvid Guterstam, first practiced brush pokes on a mannequin, using environmental visual cues to help him position the brush. Once he calibrated himself as to where the invisible body would be located, he was able to deliver brush touches to the correct body locations to create the illusion.
The researchers then repeated the mannequin experiment, without the mannequin present. The experimenter would touch the volunteer’s body with a brush. Through the VR goggles, the volunteer saw a brush touching empty space. After a few touches on different parts of the body, the volunteer had the strong experience that his body was in fact invisible.
The subject’s feeling of inhabiting an invisible body was confirmed not only by what he reported, but also more dramatically. The researcher used a knife to stab toward the abdomen of the invisible body! The volunteer flinched, and sensors detected that his wrists became sweaty, as if he were under a physical threat.
Being Invisible Reduces Social Stress
The researchers then showed that being invisible reduces social stress. A scientist slowly lifted the volunteer’s chin until he was facing straight ahead. At the same time, the VR display played a pre-recorded video showing the room coming into view. The room contained a large group of serious-looking people looking directly at the volunteer.
Standing close to a crowd of strangers who are staring at you is uncomfortable for many people. Thus, this provided a stressful situation to test how an invisible person would react.
The results showed that the illusion created was quite convincing:
– In the absence of touching that caused the volunteer to relocate his sense of self, confronting a room full of strangers caused increased stress, as reported by the volunteer and as shown by an increased rate of heart beat.
– When the volunteer felt that he inhabited a naked mannequin’s body, the stress he reported upon facing the strangers was even higher, which is perhaps not surprising.
– When the volunteer inhabited an invisible body, he felt relaxed and showed a lower heart rate.
Thus the stress of a social confrontation significantly changed, up or down, by the convincing feeling of being either a naked figure or an invisible person.
Science Speculation: The ease with which we can be fooled into inhabiting another body, and also an invisible body, is more than a parlor trick. Here are some of the practical applications, in increasing order of speculativeness.
Phantom Limb Pain in Amputees
Individuals who have a leg or an arm amputated still have the lifelong experience of having the limb, plus the neuromuscular connections leading up to the stump. Typically, amputees experience feelings, including pain, associated with the missing limb. These may be classed as “stump” or “phantom limb” sensations, depending on whether the person perceives the feelings as originating in the stump or in an invisible arm or leg.
When a patient feels phantom limb pain as a clenching or painful position of a missing arm, one of the treatments that can help is the use of a “mirror box.” A mirror creates the illusion of both arms being present. The patient may be able to gain relief from discomfort by clenching and unclenching the arm he still has, while trying to duplicate the motion with the missing arm. Arm massage in the mirror box may also help. However, in general, total cures for phantom limb pain are still unknown.
The Ehrsson experiments effectively create a phantom limb, or even an entire phantom body, in non-amputees. Researchers have used stroking or stretching of an invisible limb to treat phantom limb pain in amputees. In addition, they have added functional MRI imaging of the participants’ brains in their studies of non-amputees. By understanding how the brain creates the phantom limb illusion, the group hopes to learn how to re-train the brains of amputees to help them reduce the discomfort associated with the missing part.
Anxiety No More
Another potential application of the “invisible body” effect is the treatment of anxiety. Anxiety disorder is the most common mental illness in the US, affecting almost one-fifth of the US population.
The Swedish researchers have already shown that inhabiting an “invisible body” reduces symptoms of stress in volunteers. There is the possibility of using this effect to relieve certain forms of clinical anxiety. The therapist begins with the invisible body illusion. The transparency of the body then gradually decreases until the patient gains better control of his symptoms.
It might also be possible to train a patient to recall and re-experience a feeling of partial or total invisibility at will. This could give him a tool with which to manage stressful situations.
I am tempted to assert that most people are accepting of their socially-assigned gender (male or female). Alas, I searched in vain for the results of attitude surveys that might prove or disprove this assumption. Instead, what I found was a significant bias toward explaining, justifying or complaining about people who do not accept the label given to them by society. I failed to discover statistics concerning personal acceptance or rejection of gender labels, perhaps because no one has been interested enough to ask the question!
I am reduced to saying that most people whom I know seem to be accepting of their apparent gender. However, it’s also true that there are many people who feel out of place or mislabeled, and aspire to be something else.
It’s hard to say whether Caitlyn Jenner and other highly visible instances of gender re-assignment represent a trend or a fad. Nevertheless, the work by Ehrsson’s group seems highly relevant. Now, anyone can feel the experience of being housed in the body of another person. Thus, someone who is considering a gender change has new tool available to try out the feeling, to see how well it fits.
There are some obvious limitations to the illusion. Nonetheless, it goes well beyond cross-dressing and enters the realm of visceral experience.
Telepresence: Long-Distance Communication & Intimacy
Now that the latest research is revealing what it takes to take ownership of another body, additional possibilities open up. As long as we can set up the synchronized perceptual cues that create and sustain the out of body illusion (perhaps with robotic brush-pokes at each location), there’s no reason that the body that hosts our presence needs to be in the same room. All that’s required is that any time delay in the communication be small enough to not break the spell.
Thus we could feel that we inhabit another person who is far away from us. This could facilitate a long-distance friendship that could either be very personal, or objectionably intrusive. We could also take sensory ownership of an avatar for multiplayer online games. Or we could inhabit a physical robot that could travel, participate in meetings, and even carry out a long-distance romance. We may not be quite ready for physical intimacy-at-a-distance. However, some companies are already hoping to benefit from a large market in “teledildonics” and robotic sex.
Besides long-distance communication, improved telepresence can enhance teleoperation of robotic vehicles. This would be especially useful if the vehicles operate in inaccessible environments such as deep underwater, inside nuclear reactors and other hazardous facilities, and in search and rescue. If the operator can convincingly inhabit the vehicle, more reliable control and better performance can be expected.
[Spoiler alert: the third Evan Olsson mystery Death By Arbitrage (published in September 2015) includes a dramatization of the benefits and the hazards of robotic immersion.]
The Ethics of Being Invisible
The Swedish researchers also hope to explore how people handle ethical dilemmas when they feel as if they are invisible. They note that Plato addressed this problem twenty-five hundred years ago with his story of the magical Ring of Gyges, which could make its wearer invisible at will.
We will sidestep the solution to the ethical puzzle that Plato ascribes to Socrates. We simply note that Ehrsson et al are concerned that advances in physical science may make true invisibility possible in the foreseeable future. Therefore, we should try to understand the ethical issues before they confront us.
I personally feel that convincing, practical invisibility will not occur very soon. Nevertheless, we the citizens of Earth have managed to misuse technology far too often. Therefore, any attempt by the social sciences to get ahead of the advancement of technology is something we should welcome and commend!
In the meanwhile, the practical applications above – pain control, anxiety, gender identity and telepresence – may offer additional tools for seeking the meaning of life.
Have you ever wished for, or had a dream about, being invisible? Do you wish to share it with other readers?
Image Credit: Adapted from “Modern Kitchen” and “Vendor,” from The Print Shop 2 Collection. Not for download or reuse.
Charles, you’re right that the military and intelligence agencies would be ready customers for invisibility technologies if they were efficient and portable. And even limited invisibility (such as invisibility to radar, or transparency in certain directions) might have practical value in certain scenarios. If significant steps forward are reported the physics of invisibility, I will want to blog about them, but at this moment the most intriguing work (in my opinion) is the Ehrsson group work on the psychological side.
Since you vote for Harry Potter’s cloak as a useful form, I would point out that if we can inhabit and control robots at a distance, the military might be able to fabricate robots that appear to be some familiar object but which can “come to life” and be controlled for passive surveillance or for acts of sabotage. A cloak with embedded nano circuits might be a convenient form for such a tele operated robot to take. Or — is that Coke can hiding an IED? No, it’s just a surveillance device dropped from a passing overhead drone, spying on us. Is your paranoia working yet?? – Art
You surprisingly don’t mention a primary desirer of true invisibility if it existed — the military. They would do just about anything to achieve or acquire invisibility for their operations and will no doubt be the primary funder of such research if it ever is achieved. Most of warfare indeed tries to simulate it as best they can, usually by camouflage but sometimes by misdirection. Submarines use a form of invisibility when they hide under a sonar-bounce layer such as a thermocline, and warplanes use another form of it when they use stealth coating.
The same desire to be invisible applies to many species that either operate under cover of darkness or adopt body coloration that effectively makes them invisible as long as they don’t move, or at least don’t move more than the natural background may be moving. Then there are chameleons who can actually change their body coloration on demand, a talent that has always been assumed (though perhaps not correctly) as a way of being invisible.
I’m voting for Harry Potter’s cloak-of-invisibility as the most likely and interesting solution on a personal level. It’s convenient, portable, transferrable, and not obvious when not being used for the intended purpose. Of course it requires magic to exist, which is something of a problem when we’re taking the scientific view of such things, but there’s always Arthur C. Clarke’s “out” for resolving that problem — magic exists until you can explain how something works, then it becomes science (taking the liberty of paraphrasing his wonderful statement).