Review by Walter Cummins
The title case study of neurologist Guy Laschziner’s exploration of “the strange and startling world of our senses” doesn’t appear until the final chapter. James, now in his sixties, has experienced synesthesia all his life. For him the two senses that merge are names and tastes. Words evoke distinct food flavors. His father’s name, Peter, tastes like tinned processed peas, his grandmother’s, Mary, like thick condensed milk. It’s not just people; place names have tastes too.
While most of the other people Leschziner considers in the book experience rare and unusual sensory perceptions before of illness or accident, James was born as a synesthete. Although shared by only a small number, according to Laschziner, the condition is not an abnormality but rather a normal condition on the spectrum of human perception, Two to four percent of the population experience one of the eighty types of synesthesia. Although writers and poets create synesthesia in their imagery, those combinations are more likely to be products of their imaginations than their perceptions, such as Keats’ “… deep-delved earth, / Tasting of Flora and the country green.” James is not imagining.
Leschziner devotes chapters to studies of people with a range of unusual sensory manifestations, most often patients he has known and treated. While their perceptions are clearly limited or idiosyncratic, they serve as dramatic extremes of the uniqueness of all our perceptions.
Paul, for example, can’t feel pain and has suffered many broken bones because of a nonfunctioning area of the limbic system, the anterior cingulate cortex, resulting from a change in a single gene called SCN9A. While all individual sensitivity to pain varies, Paul has the extreme of none, including psychological pain. He lacks the warning system that signals a danger to almost all of us.
Nina lost most of her vision from a flu at age two, later undergoing a series of surgeries that finally resulted in her seeing shapes that she calls cartoonish zombie faces. She understands that they are hallucinations in the category of Charles Bonnet syndrome, named for a Swiss lawyer who wrote a 1760 essay about the visions experienced by his grandfather after cataract surgery. While these visions mirror those pf psychosis, they are not example of madness but products of a malady in the workings of the brain.
Leschziner’s point in explaining the causal details of cases like James’, Paul’s, and Nina’s is to illustrate “the loose nature of the relationship between the physical world and our experience of it.” He considers how our senses are “our windows on reality, the conduits between our internal and external lives.” While the perceptual distortions of the people he considers in his chapters are rare, his purpose is not an exposure of freak show display but rather to demonstrate that all human perception is a “complex reconstruction” resulting from the workings of our individual minds and nervous systems:
What we believe to be a precise representation of the world around us is nothing more than an illusion. Layer upon layer of processing of sensory information, and the interpretation of that information according to our expectations.
Those expectations use our internal model for understanding the world to provide the most plausible interpretation what we think we are perceiving. And that model will differ to some degree for each of us. When sensory inputs are limited or distorted by physiological and neurological conditions our assumptions about the reality can become confused beyond the plausible. Even for those of us who are considered to possess “normal” perceptions, “reality and perception are two very different things.” Our perception of the physical world results from the distinct workings of our neurological systems. It can be dangerous to believe our personal knowledge of the world represents an absolute truth.
Leschziner, while considering a range of new examples, is not breaking new ground is this book. In fact, its very title seems a conscious emulation of Oliver Sacks’ The Man Who Mistook His Wife for a Hat. In that book Sacks offers an explanation of the differences between perception and reality that Leschinzer shares:
Every act of perception is to some degree an act of creation, and every act of memory is to some degree an act of imagination.
Sacks has said, “When people die, they cannot be replaced.” Yet their example can live on, and that is what Leschinzer achieves in writing books that continue Sacks’ work.