杏吧原创

Goggles that warp your vision might be the key to understanding the redness of red, the softness of velvet and the nature of consciousness itself

A MAN walks confidently towards an open gate but instead of going straight through he raises his knee very high as if he were stepping over a low wall. He strides forward, reaching out to shake a friend鈥檚 hand. But again he misjudges, and his friend draws back in alarm to avoid being punched in the nose.

This is Innsbruck, Austria, in the 1950s, and no, the man hasn鈥檛 been drinking too much schnapps. He is psychologist Ivo Kohler, and he is wearing a pair of goggles with a built-in mirror that turns his world upside down. that records his stumblings, the eternally surprised Kohler dives to catch a child鈥檚 balloon drifting skywards and turns a teacup upside down against a stream of water being poured from above.

Kohler is just one in a long line of researchers who have used inverting goggles to try to understand how we see. The latest to pass through the looking glass is a young philosopher called Jan Degenaar. For him, however, the experiment is not simply an exploration of vision. By stepping outside his normal perception of the world and seeing it in a different way, he thinks he has gained an insight into the so-called hard problem of consciousness 鈥� how to explain the feeling of sensation. How do our brains turn a set of signals into the redness of a rose, the softness of velvet, the pungency of raw onion, and all the rest? His experience supports a new theory about consciousness 鈥� that it is not merely in the mind, but extends beyond the boundary of the body. The idea is not just weird and esoteric, if correct it has ramifications in fields ranging from animal consciousness to robotics.

Turning your world upside down (Image: Darius Kuzmickast/cameraobscuraproject.com)

Degenaar鈥檚 foray into the hard problem of consciousness began with an interest in visual perception. Orthodox understanding of how this works dates back to the 16th century and French philosopher Ren茅 Descartes, who suggested that our brains construct an internal model of the world, which we then view like a cinema playing inside our heads. Degenaar is among a growing number of researchers who question this interpretation. In 2011, while studying for a PhD at the University of Groningen in the Netherlands, he was reading descriptions of experiments with inverting goggles when he noticed something interesting. While some experimenters described the mental image of the world flipping, others related how they learned to adapt their behaviour to the inverted image. Intrigued by the discrepancy, he decided to try the experiment for himself.

Degenaar鈥檚 goggles flipped the left and right sides of space by placing a right-angled prism in front of each eye. He wore them for an average of 4 hours a day for 31 days 鈥� earlier experiments having shown that you can adapt without wearing them all the time. With objects on his left now appearing on his right and vice versa, he immediately experienced a major conflict between the feedback from his visual system and other sensory input, especially touch. He became as clumsy as Kohler. Initially, however, the most disturbing aspect of the experience was his sense of visual instability. Each time he moved his head, the scene rushed past him and he couldn鈥檛 track anything in it. On the first day, the nausea this induced was so intense that he vomited.

The visual instability gradually eased and had vanished entirely by day 13. At that point, Degenaar could move his head while keeping his gaze fixed and see objects where he expected to see them. If he kept his head still, however, he had to think hard about which way to move his eyes to bring an object into the centre of his vision from the periphery. Other skills returned at different rates. Unable to orient a knife correctly with respect to a tomato on day 1, for example, he managed to cook a simple meal three days later. He developed strategies for walking that involved turning his head in the direction he wanted to go in. At first his path zigzagged but it gradually straightened out, and on day 15 he was able to walk home from the university, armed with a white stick 鈥� though it took him an hour rather than the usual 30 minutes ().

This piecemeal adaptation has been reported by others. American psychologist George Stratton was a pioneer of inverting glasses in the late 19th century. With one eye covered, he strapped a contraption over the other, inverting the world left-right and up-down. He reported that different elements of the scene 鈥渞ighted鈥� themselves at different times and in different contexts. In the 1960s, a volunteer working with psychologist James Taylor at the University of Cape Town, South Africa, got quite good at riding a bike around the campus wearing left-right inverting glasses. However, even when he could easily navigate between buildings, writing on signs on those buildings still appeared reversed, only becoming legible after he had practised reading with the goggles.

Illusion of reality

Everyone agrees that describing inversion effects to people who have never experienced them is extremely difficult, and researchers argue over the meaning of past accounts. In Stratton鈥檚 case, for example, what was 鈥渞ighted鈥� could have been either his visual experience, or his behavioural response to it. What is consistent in most reports, though, is the incremental nature of the adaptation. For Degenaar and his former mentor, Erik Myin at the University of Antwerp in Belgium, it represents a nail in the coffin of the Cartesian model of vision.

鈥淭here is no internal image in the brain, and nothing flips,鈥� says Degenaar. The real nature of visual perception is quite different, he says. At any given time we see only a tiny portion of the visual scene 鈥� the part our eyes are actively exploring. The impression we have of gazing out on a unified visual world is mere illusion, he believes, arising from the knowledge that we would see another portion of the scene if we were to move our eyes there. It鈥檚 our active, if partial, sampling of the scene that gives it the quality of reality. In his view, adaptation to inverting glasses involves learning a new set of relationships between our movements and the changes in sensory input they now generate. It therefore depends on how much a person has practised a certain action, which could explain the staged return of consistent, accurate visual judgement. 鈥淵ou start to see vision not as one capacity, but as a set of interrelated capacities,鈥� says Myin.

One person who agrees with this interpretation is Kevin O鈥橰egan, who is based, ironically, at Paris Descartes University in France, and in whose lab Degenaar works. 鈥淪eeing involves actively interacting with the world,鈥� he says. There is no Cartesian cinema playing inside our heads, just a mass of different interactions between our senses and our environment. 鈥淪aying that we have the impression of a coherent visual field is simply an abbreviated way of saying that we are comfortable with all the ways that we visually interact with the world.鈥� He gives an example the rest of us might just be able to relate to: shaving or putting on make-up in a mirror isn鈥檛 easy the first time you do it, but with practice you get better. You reach out with your razor or mascara wand to the right place on your face, and you do so automatically, without telling yourself to do the opposite of what feels right.

O鈥橰egan鈥檚 model is not simply about vision, it encompasses all forms of perception. A decade ago, when he began talking about his 鈥渟ensorimotor theory of perception鈥�, it was highly controversial. Today, enactivism 鈥� as variants of it are collectively called 鈥� is gaining in popularity. Enactivists believe that thinking and feeling arise in the dynamic interaction between an organism and its environment. Thus an organism 鈥渆nacts鈥� a world. And this insight might help crack one of the biggest mysteries of all 鈥� the hard problem of consciousness. In O鈥橰egan鈥檚 model, your subjective experience of being is created by your awareness of the myriad different ways your self interacts with the world as you move around and explore it.

If O鈥橰egan is correct, the particular senses with which you explore the world shape your subjective feeling of being. And that鈥檚 where inverting goggles come in. Degenaar had an insight into the hard problem of consciousness around day 30 of his experiment. Until then, he had found that coordinating his movements with what he saw required effort, and he had begun to worry that he would only ever be able to compensate for his impairment, never really adapt to it. That changed when he suddenly noticed that objects appeared to be where they actually were. In his write-up of the experiment, he describes what happened next: 鈥淎 few moments later, when I had not moved my head for a while, I fell back in the other way of experiencing the visual field again, so that the objects once again appeared to be in places where they were not actually located. But when I continued looking around again, by slowly moving my head, I could now see objects where they were.鈥� In other words, he now had access to two perceptual worlds, whereas most of us spend our whole lives trapped inside one.

Previous goggle-wearers have described a stage where they saw two versions of the same object, one more ghostly than the other, though with time the ghostly one became more substantial until it replaced the first. Degenaar鈥檚 experience was slightly different: his two 鈥減ercepts鈥� were rivals. He compares this bi-stable state to what people experience when they look at an ambiguous image such as the Necker cube or duck/rabbit illusion. 鈥淚t can鈥檛 be described as the flipping of an image,鈥� he says. 鈥淚t鈥檚 more like a gestalt switch.鈥� He was seeing the same objects, and nothing had moved, but the raw feel of seeing had changed. The reason, he thinks, is that his sensorimotor engagement with the world 鈥� the bodily act of seeing 鈥� had also been transformed.

鈥淗e was seeing the same object but the raw feeling of seeing had changed鈥�

Enactivism hasn鈥檛 won everybody over. One sceptic is Colin Klein, a philosopher at the Australian National University in Canberra. While impressed by Degenaar鈥檚 descriptive powers, he says they still leave room for different interpretations. The perceptual breakthrough he recorded on day 30, for instance, could have been the result of his brain learning to extract information from an inverted internal image 鈥� in the same way that a trained sonographer can decode an ultrasound image that appears to a patient as meaningless black and white splodges. 鈥淚n one sense they are seeing the same image, but one is seeing it with expert knowledge and one isn鈥檛,鈥� says Klein.

Jesse Prinz, a philosopher at the City University of New York, expresses similar reservations. When you look in a mirror, he says, 鈥淵ou know the image is reversed, but you develop the skills to cope with a world that has been turned backwards.鈥�

Both Klein and Prinz cite a study from 1999 that circumvents the problem of describing what it feels like to experience visual inversion. David Linden, then at the Max Planck Institute for Brain Research in Frankfurt, Germany, and colleagues, tested four wearers of up-down inverting goggles on a simple visual trick that involved showing them discs drawn on a flat, grey background and shaded vertically from white to black. Normally, observers assume that the discs are lit from above, and see those that are white at the top as convex and those that are black at the top as concave (see Illustration). Linden鈥檚 volunteers made this assumption too, but when they put the glasses on they reported that the discs they had originally seen as convex were now concave and vice versa. What鈥檚 more, this interpretation persisted throughout the 10-day experiment, despite the fact that they adapted behaviourally to the glasses ().FIG-mg29901301.jpg

For Klein and Prinz, this is clear evidence for a picture model of vision. The internal image is inverted by the goggles and does not adapt or flip; rather, behaviour adapts to the inverted image. For Degenaar and O鈥橰egan, it merely demonstrates that vision can be fragmented until a person relearns all the ways in which they can interact visually with their environment.

The two interpretations have different implications. A robot built on the picture model would passively register a photo-like image of the world, while a sensorimotor robot would learn to see the world by actively exploring it. More fundamentally, if the sensorimotor approach is correct, a newborn baby might have to learn consciousness. And the quality of another species鈥� consciousness might differ radically from our own, given that it explores the world with different senses, such as eyes on the side of its head or the ability to echolocate or sense magnetic fields.

O鈥橰egan鈥檚 ultimate goal is to understand how the brain mediates these sensorimotor interactions to create phenomenological experience: how, for example, it generates a feeling of redness across all the different conditions in which a red object can be observed. At root, he thinks, raw feel springs from something elementary and predictable 鈥� the laws of physics 鈥� but understanding how it does so could give us an insight into what it means to be human. Imagery, symbolism, metaphor and language 鈥� the things that set our species apart 鈥� are, after all, grounded in sensory experience.

The debate over the hard problem continues, and we surely haven鈥檛 seen the last of inversion goggles. Degenaar would like to repeat his experiment with a group of volunteers, having them describe their visual experiences while observers simultaneously record changes in their behaviour. So look out for people trying to spoon soup into their foreheads, or throwing themselves to the ground in an attempt to stand up straight. They will be doing it in a good cause.

This article appeared in print under the headline 鈥淕oggle eyed鈥�