A few years ago, I was lying sick in bed when I received a very nice email. A neuroscientist named David Linden had sent me a link to his blog entry that referenced an essay I’d written remembering my father. Ten seconds of Googling later, I was pretty impressed with my new friend, the author of two best-selling brain books, “The Accidental Mind” and “The Compass of Pleasure: How Our Brains Make Fatty Foods, Orgasm, Exercise, Marijuana, Generosity, Vodka, Learning, and Gambling Feel So Good.” I read both, smitten with Linden’s combination of storytelling, humor and amazing things you didn’t know about the brain.
We spent the next year becoming close, during which time he began working on his latest book, “Touch: The Science of Hand, Heart, and Mind.” I, on the other hand, began working on a dating memoir called “Highs in the Low Fifties,” in which he appears as The Brainiac.
Like David’s other books, “Touch” uses personal anecdotes to introduce scientific concepts. Given the topic, these stories are often pretty hot. But since I recently played a role in setting him up with his current girlfriend, the food editor of this magazine, I didn’t think she’d mind if we talked about, um, sex.
MW: I was just rereading Chapter 3, which opens with a story about when you had jury duty in Baltimore City on an intensely serious trial, which arose from an alleged sex criminal literally being “rubbed the wrong way.” Why do some caresses drive us crazy in a good way and others the opposite?
DL: We humans are highly evolved for social interaction. We can interpret in exquisite detail the tone of someone’s voice, the direction of their gaze or their facial expression. The same is true of social touching. When asked to rate caresses on the arm, most people zero in on the same ideal: a caress delivered with light-to-moderate force at a speed of about one to two inches per second.
MW: That’s pretty precise!
DL: That’s because the features of an ideal caress are not determined in the brain but in a special type of caress-sensing nerve ending [called C-tactile fibers] found only in hairy skin. These fibers send their signals to a part of the brain which is specialized for interpreting the emotional content of touching.
MW: Hairy skin? But aren’t most of our erogenous zones pretty smooth?
DL: Even seemingly smooth spots like the cheek, inner arm and inner thigh are covered in fine hairs. The C-tactile nerve endings wrap around the hair follicles to sense hair deflection during a caress. The nerve endings responsible for sexual sensation are a different type, found in the hairless skin of the genitals and to a lesser degree in the lips and the nipples. It’s called a mucocutaneous end-organ…
DL: In German it’s even better: Genitalnervenkörperchen.
MW: And yet we can’t read Braille with our genitals, I seem to remember.
DL: If readers of my book retain one fact for cocktail party chatter, it’s that. Although the hairless skin of the genitals is very sensitive—it can detect a very light touch—it cannot locate the touch with great precision. It’s similar to the cornea of the eye in that respect. A tiny bit of grit in the eye will hurt like hell but where it is can be hard to determine.
The portions of the skin that have fine resolution of texture and form, like the fingertips, lips and tongue, have a different nerve ending, called a Merkel complex, specialized for that job. The clitoris and glans penis almost completely lack Merkel endings and so they fail at Braille reading.
MW: Yet who can fault them when they are so good at other things? On another note, one of the pleasures of our friendship has been talking about books. What writers have influenced you?
DL: One of my favorite science writers is Olivia Judson, a former Baltimorean and the author of “Dr. Tatiana’s Sex Advice to All Creation.” Judson’s shtick is that she’s a sex advice columnist for animals: “Dear Dr. Tatiana, I’m a Madagascar stick insect female and this male has been on my back mating with me for three days. Why does he do it and how can I get him to stop?” She uses this comic device to get at some rather sophisticated issues in the evolutionary biology of sex.
Science books are fun, but I mostly read contemporary fiction. I have particularly enjoyed some of the recent novels that have had scientists as their main characters like Elizabeth Gilbert’s “The Signature of All Things” and Lily King’s “Euphoria.”
MW: A man who knows his way around a bookstore AND a nervenkörperchen… sigh.
David Linden will be reading and signing books at the Ivy Bookshop (6080 Falls Road, Baltimore) on Wednesday, Feb. 11, at 7 p.m. theivybookshop.com