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. To gracefully avoid an embarrassing situation. To experience the power of seeing without being seen. Or perhaps, to plunder Fort Knox?
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 and 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 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, with some of the newest work in China using nothing more complicated than mirrors and glass prisms. The illusion is of 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, because science is far from achieving that at this time. What science has now achieved is to make you feel invisible. After we discuss the work, we’ll talk about its amazing potential applications, ranging over help to amputees, 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 invented in 1998 by Botvinick and Cohen, two psychologists at Carnegie Mellon University.
Here’s how we might duplicate their experiment today: our volunteer, call him Victor, would be seated 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 and 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, at the same time and at corresponding positions on each hand.
In the CMU study, after ten minutes each volunteer completed a questionnaire. It asked first for an open-ended description of their experience, then 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,” such as “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. They were able to extend the rubber hand illusion to the entire body with the clever use of virtual reality (VR) goggles, making a volunteer feel that he was outside his own body, or even housed in someone else’s body. This is the psychological version of the currently-impossible Head Transplant that we previously discussed.
Based on the earlier “rubber hand” work, the researchers believed that two elements would be essential for creating a strong illusion: 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 were sent to 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 was substituted for 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 that he was 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. However, 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 and 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 mannequin experiment was then repeated, 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, filled with 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, so 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 was strongly affected, 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, that are 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 phantom limb pain is experienced 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 is used to create 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 amputated 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. The 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, starting with an invisible body and gradually reducing its transparency until the patient feels in 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, giving him a tool with which to manage stressful situations.
I am tempted to assert that most people are satisfied with their socially-assigned gender (male or female), and I searched for the results of attitude surveys that might prove or disprove this assumption. Alas, what I found was a significant bias toward explaining, justifying or complaining about people who are not satisfied with 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 that anyone can experience being housed in the body of another person, someone who is considering a gender change has one more tool available to try out the feeling, to see how well it fits. There are some obvious limitations to the illusion, but 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 – long-distance friendship that you might consider to be either 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, but 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, especially those that need to function 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. Pre-publication alert: the next Evan Olsson mystery Death By Arbitrage (to be published in fall 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 and 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 we are confronted with them.
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 to be welcomed and commended.
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.