Rats! Turns out a kiss is just a kiss

Re­search an­swers Vic­tor ‘How did it hap­pen that Hugo’s 19th cen­tury ques­tion their lips came to­gether?’

Herald on Sunday - - Front Page -

THE ul­ti­mate ro­man­tic ex­pres­sion started out as a prim­i­tive, chem­i­cal form of com­mu­ni­ca­tion be­tween rat-like an­ces­tors of hu­mans, ac­cord­ing to Roger High­field, Daily Tele­graph Science Ed­i­tor.

A kiss is more than just a kiss. Kiss­ing is a sym­bol of ro­mance, love and af­fec­tion. A po­lite peck is an ac­cepted greet­ing be­tween friends and fam­ily. A hun­gry snog a sym­bol of base de­sire. In the Bi­ble, a sly smacker is even a sym­bol of be­trayal.

Now the re­sources of science are be­ing ap­plied to shed new light on this most pow­er­ful ges­ture.

The ques­tion of ‘‘what’s in a kiss’’ has taxed lovers, po­ets and sci­en­tists through­out the ages.

Dr Henry Gib­bons de­fined it as: ‘‘The anatom­i­cal jux­ta­po­si­tion of two or­bic­u­laris oris mus­cles in a state of con­trac­tion’’, while, in Cyrano de Berg­erac, Ed­mond Ro­stand said it was a ‘‘rosy dot placed on the ‘i’ in lov­ing’’.

The phys­i­cal na­ture of a kiss was first re­vealed a few years ago in de­tail by an an­i­mated scan of a ver­ti­cal cross-sec­tion through the head, made by Elaine Sas­soon, Annabelle Dytham, Robert Scully and Pro­fes­sor Gus McGrouther at the Rayne In­sti­tute in Univer­sity Col­lege Lon­don.

The scan re­vealed that a kiss is mostly due to the squash­ing of a pair of mus­cles with a J-shaped cross­sec­tion, draw­ing on all 34 fa­cial mus­cles for suc­cess.

‘‘Not only do you use your fa­cial mus­cles in kiss­ing, but ap­prox­i­mately 112 pos­tural mus­cles as well,’’ added Pro­fes­sor McGrouther, now at the Univer­sity of Manch­ester.

Kisses are an­cient, an echo of a more prim­i­tive, chem­i­cal, form of com­mu­ni­ca­tion, ac­cord­ing to stud­ies of mice by Kazushige Touhara and col­leagues at the Univer­sity of Tokyo.

The team has found non-volatile pheromones — sig­nalling mol­e­cules — se­creted from the eyes and trans­mit­ted by di­rect con­tact re­veal what sex a mouse is to its peers. Al­though mice and hu­mans are very sim­i­lar at a ge­netic level, the gene en­cod­ing this pheromone does not ex­ist in the hu­man ge­netic make-up.

‘‘We lost this gene some­where dur­ing evo­lu­tion,’’ he said.

But mice and men are thought to share a com­mon an­ces­tor that lived be­tween 75 and 125 mil­lion years ago, a rat-like crea­ture called Eo­maia scan­so­ria ( Eo­maia, Greek for ‘‘an­cient mother’’ and scan­so­ria, Latin for ‘‘climber’’) and Dr Touhara spec­u­lates that hu­mans may re­tain a ves­tige of ro­dent be­hav­iour be­cause we still like to kiss or rub noses, de­pend­ing on the cul­ture, to max­imise the chance of sam­pling an­other’s aroma, per­haps even to savour a non-volatile pheromone that sig­nals de­sire.

In other words, a smooch, peck or smacker may be an echo of the way our furry an­ces­tors once sig­nalled to each other.

One head-turn­ing ob­ser­va­tion of kiss­ing was re­ported re­cently by Pro­fes­sor Onur Gun­turkun of Bochum Univer­sity in Ger­many, who had watched 124 cou­ples in ac­tion at air­ports, rail­way sta­tions, parks and beaches across the United States, Ger­many and Turkey.

His sur­vey of 13 to 70-year-olds showed that twice as many peo­ple turned their heads to the right to kiss as to the left.

It is no ac­ci­dent that in Rodin’s mas­ter­piece The Kiss, the lovers also turn their heads to the right. This is one of many ex­am­ples of a righthanded pref­er­ence: use of the right foot, eye and ear are also pre­ferred with a ra­tio of 2:1.

Dur­ing the fi­nal weeks in the womb, ba­bies de­velop a pref­er­ence for turn­ing their heads to the right and his find­ings sug­gested that this pref­er­ence lasts into adult­hood, and, by set­ting up bi­ases in move­ment and sen­sory per­cep­tion, may in­flu­ence other be­havioural asym­me­tries.

Now this fas­ci­nat­ing in­sight kiss­ing has been con­firmed.

‘‘A few weeks ago, an Ir­ish study ap­peared that could show that kiss­ing a doll’s face re­sults in the same asym­me­try as kiss­ing a per­son,’’ he said.

Armed with this data, and from a new study he is con­duct­ing, Pro­fes­sor Gun­turkun is able to pre­dict over­all kiss­ing suc­cess rate, as­sum­ing that the in­di­vid­ual kiss­ing ‘‘head-mo­tor bias’’ to the right is 2:1.

Of nine cou­ples, four would both have the right bias, en­sur­ing a suc­cess­ful kiss. One cou­ple would have a left bias, again en­sur­ing good ini­tial con­tact. How­ever, four cou­ples would clash noses as they at­tempted a left/ right kiss and fail to en­sure good ini­tial lip-to-lip con­tact.

A few days ago, an in­sight into the en­dur­ing nose prob­lem

into

in­trigu­ing was pub­lished in the jour­nal Na­ture Neu­ro­science by Martin Sereno and Ruey-Song Huang of the Univer­sity of Cal­i­for­nia, San Diego. Plant­ing a kiss on the lips, and avoid­ing the nose, re­quires ‘‘prompt, co­or­di­nated pro­cess­ing of spa­tial vis­ual and so­matosen­sory in­for­ma­tion,’’ said Dr Sereno. That co-or­di­na­tion goes on in our heads, where we and our sur­round­ings are rep­re­sented.

Neu­ro­sur­geon Wilder Pen­field is cred­ited with es­tab­lish­ing half a cen­tury ago that a map of the hu­man body ex­ists in the brain, with spe­cific ar­eas of the cor­tex pro­cess­ing in­for­ma­tion from dif­fer­ent body ar­eas. This is a to­po­graphic map of the body, where sig­nals from ad­ja­cent fin­gers map to ad­ja­cent parts of the brain. Other parts of the brain con­tain maps of the retina, first re­vealed by the ef­fects on vi­sion of gun­shot wounds to the head of World War I vet­er­ans. Us­ing a brain scan­ner method called func­tional mag­netic res­o­nance imag­ing, the Cal­i­for­nian team re­vealed changes in blood flow go­ing to a part of the brain called the ven­tral in­tra­pari­etal area. It in­te­grates in­for­ma­tion rel­e­vant to the face (as dis­tinct from the ‘‘fusiform face area’’ un­der the tem­po­ral lobe, that tells you whose face you are kiss­ing).

As they did this, they var­ied the an­gle of air puffs to the face or moved seg­ments of a video ( Xena: War­rior Princess) around on a screen close to the per­son’s face. They found aligned maps of touch and vis­ual stim­uli where nerve cells in the same re­gion of the brain re­sponded to ei­ther the touch or the sight of an ob­ject near the face, such as the brush of an­other’s lips on the up­per right cheek, or the sight of those lips in the up­per-right side of vi­sion.

That re­gion in the su­pe­rior part of the post­cen­tral sul­cus may play a cen­tral role in plant­ing a kiss, since it helps com­bine vis­ual and touch in­for­ma­tion about ob­jects.

‘‘The idea that the peo­ple who are clumsy with their head might have poorly tuned-up VIP/frontal cir­cuitry is a nat­u­ral hy­poth­e­sis given what we have found,’’ said Dr Sereno.

Now we can an­swer the ques­tion posed in the by 19th cen­tury by the French poet Vic­tor Hugo: ‘‘How did it hap­pen that their lips came to­gether?’’

We know ex­actly how. Ex­er­cise all 34 fa­cial mus­cles, an­other 112 pos­tural ones, turn the head to the right and move for­ward in one smooth move­ment to suc­tion.

Pay trib­ute to that 125 mil­lionyearclimb­ing-rat like mam­mal by savour­ing the non- volatile pheromones. It’s easy re­ally.

Tele­graph Group Ltd

SMOOCH: Plant­ing a kiss on the lips re­quires prompt, co­or­di­nated pro­cess­ing of vis­ual and sen­sory in­put. CUL­TURAL TRAIT: Rub­bing noses, like a kiss, is an an­cient prac­tice and a way of sam­pling an­other’s aroma.

PECK: Ge­net­i­cally mice and hu­mans are sim­i­lar, and both kiss.

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