Folk illusions – more than child’s play

Have you ever seen a rubber pencil? We wager you have, though it probably was not a real rubber pencil. In a performance of Rubber Pencil, a pencil or pen is grasped between the index-finger and thumb and then wiggled in such a way that its translational and rotational movement creates the visual illusion of a rubbery pencil bending back and forth.

We have observed children as young as seven performing Rubber Pencil. Upon seeing an older playmate perform the trick, one five-year-old in Bloomington, Indiana – who had not yet developed the necessary coordination and dexterity to perform it himself – exclaimed confidently, 'That's an optical illusion!' In their play with Rubber Pencil, children and youths challenge the correlative folk idea: seeing is believing. This raises an important question: What does the fact of children's awareness that seeing is not always believing tell us about perception and perceptual illusions more generally?

Naive amazement?

In the scientific, philosophical and popular literature about illusions, writers generally imagine that the average person on the street responds to the experience of a perceptual illusion in one of two ways. The first stems from a supposed deep-seated naivety as to the nature of perception.

Consider these examples. In his chapter on sensation and perception in the 2012 Handbook of Psychology, Stanley Coren writes: 'Most people have a naïve, realistic faith in the ability of our senses to convey an accurate picture of the world to us. For the proverbial "man on the street," there is no perceptual problem. You open your eyes and the world is there.' And in The Science of Illusions, Jacques Ninio writes: 'One illusion, possibly the strongest of all, is the one that makes us believe that we have a direct hold on reality. The work of interpretation conducted by perception never comes to light and leaves no other trace than its final result.'

In this line of thinking, when people experience illusory perceptions, their naivety manifests in crisis-like surprise. We see this in a report in The Psychologist of a wonderful hands-on public event at the British Psychological Society's 2016 Annual Conference: 'Visual and multi-sensory illusions made people question their senses, the velvet hand illusion produced, in many people, an odd feeling of their hands melting into one another and the Beuchet Chair allowed people to have fun with forced perspective… Visitors left wondering whether they could trust their senses, not quite believing their eyes and questioning reality.'

Our work with folk illusions leads us to conclude that illusory experiences – even these carefully planned illusions performed at the Society's public event – do not force people to question their realities in a serious way. They express surprise and delight, and may even admit that they can't believe everything they see, but they do not change their immediate behavioural patterns in unusual ways. They will grab their friend's arm without fear of their hand melting into it, or drive their cars without doubting the size or location of other vehicles. Rather, the broad pattern we have recognised from observing and talking to people about folk illusions is that we respond to illusions by adding a specific new context to our general understanding that reality can be complex and elusive. Anyone who has had their nose 'pulled off' by a trickster uncle or who has tried to pat their head while rubbing their belly will know quite well that the body can be strange. The joy and amazement psychologists witnessed at the public event was not so much a response to the whole phenomenon of illusion but to the specific illusions that had never before been experienced, all surrounded by the allure of science!

The gaps between perception and conception

The second response to illusory experience is more philosophical – extending back at least to Aristotle, for whom illusion was a tool for helping people understand how perception works more generally. Psychologists are familiar with illusions' usefulness in illuminating the mechanisms of perception. As Richard Gregory teaches, 'The brain's perceptual knowledge-base is not the same as its conceptual knowledge-base.' Illusions uncover the gaps between perception and conception. We have learned that these gaps are just as recognisable in folkloric activities like Rubber Pencil as they are in the scientist's lab. This second response – rather than naive amazement – more accurately characterises how people situate illusory experiences within the panoply of everyday perceptions.

Kids, for example, play with a variety of tactile illusions focused on the hands, similar to the Velvet Hand illusion displayed at the fair. In one we call Touching Invisible Glass (see photo above, demonstrated by Aoife, age 8), the actor is instructed to place her hands in front of her chest with palms facing each other, fingers splayed, and only the fingertips touching together. She then pumps the palms of the hands closer together and farther apart rapidly in succession, always keeping the fingertips touching. After about 15–30 seconds of activity the actor feels as though something invisible, like 'a pane of glass' or 'a force field', obstructs the fingertips from touching.

Another well-known form is Dead Man's Hand. Two kids face each other and press one palm flat against the opposite palm of their partner with fingers aligned. The director rubs the dorsal side of the two middle fingers vertically with his free index finger and thumb. The actor's fingers feel as though they are a part of the other's body and they feel coarse and numb – or 'dead'. Participants usually take turns acting as director so each one can feel the macabre sensation.

We have collected 15 different haptic illusions featuring the fingers and/or hands. Kids delight in this play. Because every form involves peculiar bodily positions – performance positions in our terminology – that lend themselves to unusual actions, the associated perceptions are not categorised with other perceptions that result from more familiar or mundane behaviours. There is no need to question reality when in fact illusions are themselves a normal sort of perception.

Piercing the veneer of perception

As traditional forms of child's play, folk illusions must be easily transmittable from person to person, so performance positions are largely achievable anytime and anywhere that kids gather for free play activities. Basic props are not rare, but any technologies employed in a folk illusion must be simple and use easily accessible materials. We have recorded, for example, uses of empty toilet-paper or paper-towel tubes, rocks, tables, and chairs. The more elaborate a prop needed for an illusion, the less likely children will have the technical skills, time or motivation to create it. What impresses us, however, is that children – making the best of their situation – are capable of piercing the veneer of perception in ways as sophisticated as illusions devised by philosophers and scientists.

Take, for example, the Beuchet Chair displayed at the Society's public event in Nottingham. This illusion requires fabricating chair parts of different sizes and placing them such that, from one perspective, a person appearing to sit in the chair looks much smaller than expected. A well-constructed Beuchet Chair creates a convincing illusion that teaches viewers, among other things, that: Others can create social perceptual contexts that force me to misperceive who is where. Consider the well-known tourist images of people holding the Eiffel Tower in their hand, or propping up the Leaning Tower of Pisa. Twenty-first-century internet variants of these pictorial illusions depend on well-timed, perspectival cues to mimic widely recognised images from popular culture – search 'Vadering' or 'Hadoukening' if you want to learn more about these kinds of digital folklore.

The same underlying idea is communicated in the folk illusion Who Is Touching You?, an attention-based illusion so elementary that the tongue-in-cheek website Uncyclopedia has dubbed it the 'Oldest Trick in the Book': 'In the year 10580 B.C.E. the Babylonian king, Hammurabi, reigned supreme over the Mesopotamian deserts. On February 30, during a long speech by Irhemhotep, he stood on Shamadad's right, and reached over and tapped him on the left shoulder. As a result, Shamadad looked to his left, where no one was standing. All would laugh…'

The agent who initiates this 'ancient' trick intuits that people normally connect the perception of an active social touch so closely with the location of the toucher that they will usually turn their head or body right away toward the side of the touch. The reaction often happens pre-consciously. Of course, the motivations for performing Who Is Touching You? vary, ranging from malicious intent to dupe a target to more benevolent initiation of rambunctious, flirtatious play with friends or romantic interests. Regardless, motivations are always coupled with traditionalised knowledge that the reliability of our perception makes us vulnerable to illusions like Who Is Touching You? Folk illusions show us that group awareness of these vulnerabilities does not lead to crisis or chaos; instead, individual vulnerabilities are re-interpreted by the group as a marker for dependence on community. Folk illusions may introduce children and youths to the strangeness of their bodies, but they simultaneously demonstrate for youthful performers that their bodies are known by their peers in just those strange ways. When friends tell a playmate that they can make their hands feel like they are touching glass, or that they can make one of their hands feel 'dead', the playmate senses that this possibility marks him as the same kind of being as his friends. This intersubjectivity at the heart of folk illusions serves not to weaken but ultimately to strengthen our sense of the reliability of our everyday perceptual processes, because those processes intimately involve the social groups of which we are members.

No strangers to illusion

We have catalogued over 70 stand-alone folk illusions, over 100 if we include variants of those forms. Folk illusions occur in every sense domain. Toddlers, witness to an older acquaintance's performance of the Detachable Thumb illusion or the aforementioned Got Your Nose trick, are engaged in traditional forms of illusory play from two years old and up. In surveys of freshmen and sophomores at Indiana University, about 88 per cent of respondents reported having played at least one folk illusion as a child. We have documented folk illusions from 11 different countries, and further research will study how widespread folk illusions are around the world. (We would be pleased to hear about more illusions – see box above.)

The pervasiveness of folk illusions indicates that most people are not strangers to illusion but only to particular illusions. The careful balance people ordinarily maintain between a working belief in plausible events and a healthy scepticism of implausible ones is fostered by the everyday coordinated interactions that people have with each other and the world. Folk illusions are set apart from the everyday world by being a recognisable genre of performance, within which it is not odd but normal and expected to experience oddities.

As folklore, children's play with illusions is based in the social. Performers of folk illusions pass along implicit knowledge embedded in the processes of transmission that is ultimately much more influential than the content of any individual folk illusion itself. So it turns out when you were amazing your friends with the rubber pencil, you were also showing them that seeing is not always believing, and that is just
plain fun!

Box: Rubber pencil

It wasn't until 1983 that experimental psychologist James Pomerantz first reported a study on the Rubber Pencil illusion, concluding that the illusion results from our tendency to use the persistence of afterimages to help categorise viewed objects.

An object moving across the visual field leaves a trace on the retina. The more rapidly the object moves, the less dense is its trace. Think of someone whirling a yo-yo around in a circle. If it is done slowly, the observer can see the individual yo-yo, but if it speeds up, the observer begins to see a single circular line that is the trace of the yo-yo's movement. At great speeds, of course, the yo-yo will almost disappear altogether. Pomerantz observed that a performance of Rubber Pencil involves two types of motion simultaneously: translational (the movement of the whole pencil up and down) and rotational (the movement of the pencil from an axis). The two movements conspire to produce the greatest density of afterimages along two curves that trace the top and bottom endpoints of both the translational and rotational movements. People fill in non-focal parts of objects that persist in vision – just the way that one sees a full circle when the yo-yo is being whirled around at the right speed – so viewers of the wiggling pencil experience a unified perception of a pencil bending.

Subsequent research, such as that led by Lore Thaler at the Ohio State University (see tinyurl.com/j794aoe) has suggested that additional factors can contribute to the perception as well. Like most illusions, the surprising perception actually results from our sensory systems' normal response to a relatively infrequent combination of conditions.

- Clai Rice is Professor of English at the University of Louisiana at Lafayette

- Brandon Barker is Lecturer of Folklore at Indiana University Bloomington

We invite readers to send us descriptions of illusions you have played at [email protected]