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The Feel of a Phantom

Posted on September 30th, by amoeboar in classes, pcomp. No Comments

From Donald Hoffman, Visual Intelligence

Hoffman argues in his book Visual Intelligence that ”everything you see you construct,” and not just sight but what you hear, smell, taste and feel. According to Hoffman, all of our sensations and perceptions are constructions.

Oftentimes, we look to touch to ground our beliefs in reality. Illusions and optical tricks are common for things we see, and being able to touch it, knock on it, wave our hand through it is what settles and dispels the illusion.

The argument Hoffman makes here is that touch is no less “constructive” than other senses. When we touch something and make out its properties, we are going through a creative process that is as active as when we “carve our visual field into distinct visual objects” (like feeling around for things to make out what they are). Considering phantom limb, we continue to create all these “feels” even in the absence of a “feeler”.

The region of the brain responsible is the somatosensory cortex, the portion devoted entirely to processing touch and related sensations. Certain sections of the cortex, when stimulated, will create sensations in specific parts of the body. Interestingly, a linear path can be “mapped” along the edges of the cortex. The section of the cortex representing the hand might be the “linking” section between the face and arm, which might explain why in the absence of a real hand, sensations might still be passed across this section of the brain when either the arm or face are stimulated.

So then, if it can be assumed that we construct all that we feel, and that we should be able to construct feeling in any body part, even if it amputated, what about the converse? If a body part is intact, but our constructive processes are not, should we have trouble with touch?

A study on a stroke patient in the early nineties showed that she had damage in a region of the parietal cortex of her left hemisphere. Afterwards, she complained that her right thumb felt numb, and that she had trouble recognizing objects in her purse using her right hand. This is known as tactile agnosia, the inability to recognize objects by touch (her left hand had no problem recognizing objects). She also had perfectly normal sensorial capabilities using her right hand; she could feel vibrations, discriminate sandpapers, approximate stick lengths, judge weights of objects, she just couldn’t put it all together to form recognizable constructs of these objects. [gn_pullquote align="right"]Your power to create what you feel is the foundation for many high-tech products now entering the market, from arcade games that place you not only in virtual visual worlds but also in virtual tactile worlds, to surgical simulators in which surgeons not only see but also feel the tissues of the virtual body on which they practice their techniques.[/gn_pullquote]

How is this related to technology? We are entering into an era of virtual touch. If the goal is to provide an experience for the user, tactile experience continues to be an important aspect to consider (I’m noticing a trend here). More than just sensory experiences such as hot or cold, tactility also refers to how my sweater might feel if one of its threads got snagged on a handrail. Instead of considering how heavy an object feels relative to another, we might consider how much resistance it creates on our palms as gravity pulls it downward.

The additional considerations to take into account are that these tactile elements extend so much farther beyond those things we touch with our hands: they include what our “guts” feel, what our minds feel, what our bodies think they feel, based on what we’re used to feeling and what we’re not familiar with feeling and what we’ve never felt before. Feeling, in this sense, has a huge role in bringing the message home. How can we re-create that lurch our stomachs feel on a roller coaster, or how the hairs on the back of our necks stand up when we catch a chill, or that unmistakable and hard-to-describe tingle we feel when we hear the scratch of fingernails on a chalkboard?

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