Why CAN’T you tickle your­self?

It’s one of Na­ture’s quirks. And the sci­ence be­hind it has fas­ci­nated ev­ery­one from Aris­to­tle to Freud

Daily Mail - - Femail Magazine - By An­to­nia Hoyle

TICK­LING can give ba­bies their first gig­gle, lull a trout into a trance and prove erotic enough a dis­trac­tion to lure a lady away from her good in­ten­tions. Yet it re­mains a bizarre and baf­fling phe­nom­e­non — loathed or loved — which con­tin­ues to in­trigue the best minds in sci­ence.

ear­lier this month, re­search pub­lished in the sci­ence jour­nal con­scious­ness And cog­ni­tion re­vealed that — con­trary to ex­perts’ pre­vi­ous un­der­stand­ing, that has stood since Greek philoso­pher Aris­to­tle laid claim to the sub­ject — it is pos­si­ble for some peo­ple to tickle them­selves.

here we in­ves­ti­gate the sci­ence be­hind the sensation.

WHY ARE WE TICK­LISH?

TICK­LING hap­pens when the skin’s nerve end­ings are stim­u­lated, send­ing a mes­sage through the ner­vous sys­tem to two sep­a­rate re­gions of the brain: the so­matosen­sory cor­tex, the area pri­mar­ily re­spon­si­ble for analysing touch, and the an­te­rior cin­gu­lated cor­tex, an area to­wards the front of the brain that con­trols emotion. com­bined, this cre­ates the tickle sensation.

TWO TYPES OF TICKLE

There are ac­tu­ally two types of tick­les: knisme­sis and gar­gale­sis. The for­mer is as­so­ci­ated with low lev­els of stim­u­la­tion to sen­si­tive parts of the body, and can be trig­gered by a light touch or by a light elec­tric cur­rent.

Knisme­sis can also be trig­gered by crawl­ing in­sects or par­a­sites, prompt­ing scratch­ing or rub­bing at the tick­lish spot, thereby re­mov­ing the pest.

‘For­tu­nately, our brains have evolved to block our re­sponse to the sensation when we are able to pre­dict what it will feel like — oth­er­wise some­thing as sim­ple as putting on our socks would turn us into a ner­vous wreck,’ says Dr emily Gross­man, an ex­pert in molec­u­lar bi­ol­ogy

Gar­gale­sis refers to harder, laugh­ter-in­duc­ing tick­ling, and in­volves the re­peated ap­pli­ca­tion of high pres­sure to sen­si­tive ar­eas.

SEN­SI­TIVE SPOTS

The soles of the feet are most peo­ple’s peak tickle spots be­cause they are filled with highly sen­si­tive nerve re­cep­tors. The armpits — an­other tick­lish area — have nu­mer­ous veins and ar­ter­ies that make them ex­tra sen­si­tive.

Our most tick­lish zones are coin­ci­den­tally our weak­est spots, such as the neck and stom­ach, and evo­lu­tion­ary bi­ol­o­gists be­lieve we laugh when th­ese ar­eas are touched as a de­fence mech­a­nism to sig­nal sub­mis­sive­ness.

‘re­search sug­gests that laugh­ter is an in­stinc­tive re­sponse to pro­tect us,’ says Dr Gross­man. ‘We’re show­ing we’re not a threat. It is a way of dif­fus­ing the sit­u­a­tion.’

BABY BAN­TER

NEU­RO­SCI­EN­TISTS be­lieve tick­ling to be an im­por­tant form of pre-ver­bal com­mu­ni­ca­tion. It al­lows ba­bies to cre­ate a dis­tinc­tion be­tween them­selves and oth­ers and can be a bond­ing ac­tiv­ity be­tween par­ent and child that also helps es­tab­lish a re­la­tion­ship of trust. ‘Tick­ling can pro­vide a so­cial func­tion to con­nect us to loved ones,’ says Dr Gross­man. ‘It makes us feel good be­cause phys­i­cal touch re­leases happy hor­mones such as oxy­tocin and dopamine, as does the laugh­ter that tick­ling trig­gers.’

Tick­ling of­ten con­tin­ues through­out child­hood be­tween sib­lings, as a way for younger teenagers to as­sert their dom­i­nance over one an­other and re­solve ar­gu­ments with­out re­sort­ing to vi­o­lence.

DE­GREES OF TICKLY

EV­ERY­ONE with func­tion­ing nerve- end­ings is sus­cep­ti­ble to the sensation of be­ing tick­led, but, as ir­ri­tat­ing as it is for any­one who re­calls los­ing out to a sib­ling in a tickle- off dur­ing child­hood, some of us are bet­ter at sens­ing when we are about to be tick­led than oth­ers, prompt­ing the cere­bel­lum — the part of the brain that pre­dicts the sen­sory con­se­quences of move­ments — to block the rest of the brain’s re­sponse to the tickle.

WHY CAN’T I TICKLE MY­SELF?

BE­CAUSE tick­ling only works when you aren’t ex­pect­ing it, most peo­ple can­not tickle them­selves.

‘As our hand moves to­wards our skin the cere­bel­lum can make its own ac­cu­rate pre­dic­tion of what it will feel like which blocks the brain’s re­sponse,’ says Dr Gross­man.

‘sim­ply watch­ing some­one else’s hand com­ing to­wards us isn’t enough to pre­dict how it’s go­ing to feel. but if you touch some­one’s hand as they’re about to tickle you it will al­low you to block the sensation as if it were your own hand and stop it tick­ling.’

... OR CAN I?

HOW­EVER, the sci­en­tists whose find­ings were pub­lished in con­scious­ness And cog­ni­tion dis­cov­ered that those dis­play­ing schiz­o­phrenic ten­den­cies — such as er­ratic be­hav­iour and the in­abil­ity to de­rive plea­sure from so­cial ex­pe­ri­ences — are more likely to be able to tickle them­selves.

re­searchers at the univer­sity of Lille in France se­lected peo­ple with schiz­o­phrenic traits to both tickle and tickle them­selves.

It emerged they didn’t find self-tick­ling to be any less tick­lish than be­ing tick­led by a third party.

This is be­lieved to be be­cause the process that tells the brain that the act of self-tick­ling is vol­un­tary is im­paired in such peo­ple, so they are more likely to re­act as if the tickle was from an ex­ter­nal cause or per­son.

NO LAUGH­ING MAT­TER

WHILE some un­doubt­edly en­joy the sensation of tick­ling, the ac­tion ac­ti­vates a part of the brain that con­trols fa­cial move­ment called the rolandic op­er­cu­lum, mak­ing you laugh even if you’re not re­ally hav­ing good time at all.

One re­cent sur­vey found 36 per cent of peo­ple ac­tively dis­liked the sensation of be­ing tick­led — and for those who aren’t fans it can be fright­en­ing and painful — so much so that it was used as a form of tor­ture by Nazi prison guards dur­ing World War II.

TICK­LED TO DEATH

‘A PHOBIA of tick­ling is quite rare — but un­der­stand­able,’ says Dr sandi mann, se­nior psy­chol­ogy lec­turer at the univer­sity of cen­tral Lan­cashire. ‘suf­fer­ers fear the lack of con­trol that comes from be­ing tick­led and the in­abil­ity to ar­tic­u­late their fear be­cause they are strug­gling to breathe. For them the say­ing “tick­led to death” is a truly scary con­cept.’

Tickle pho­bias are likely to be trig­gered by an event in child­hood, from a tick­ling in­ci­dent to some sort of bois­ter­ous horseplay. Dr mann says: ‘Treat­ment would in­volve grad­ual ex­po­sure to tick­ling to de­sen­si­tise the suf­ferer.’

TICKLE THROUGH TIME

The phe­nom­e­non has long trou­bled philoso­phers, and un­til the 19th cen­tury it was widely be­lieved tick­ling and hu­mour were linked.

charles Dar­win and psy­chi­a­trist ewald hecker con­sol­i­dated this the­ory with the Dar­win-hecker hy­poth­e­sis that stated hu­mans would only laugh when tick­led if in a good mood .

SLAP AND TICKLE

SIG­MUND Freud was fas­ci­nated by tick­ling and sex as part of his plea­sure-pain prin­ci­ple. he wrote a lot about the ‘rhythm ’ and the ‘rises and falls in the quan­tity of stim­u­lus’ in types of tick­ling.

sex ex­pert Lucy Jones says the neck, shoul­der and back are among the most pop­u­lar eroge­nous zones for lovers to tickle one an­other.

‘Not only does tick­ling re­lease feel­good hor­mones that help us bond with our part­ner, it serves as an in­tro­duc­tion to a phys­i­cal re­la­tion­ship; a com­fort­ing way of ex­plor­ing our bod­ies with­out be­ing overtly sex­ual,’ she says.

AN­I­MAL KING­DOM

ARIS­TO­TLE’s the­ory that only hu­mans are in­tel­li­gent enough to re­spond to tick­ling is not strictly true: some an­i­mals rely on knisme­sis to help them shake off other an­i­mals or in­sects that are a threat.

horses shud­der to get flies off their backs. Trout, mean­while, go into a trance when rubbed on their un­der­belly, as do rab­bits when turned on their backs and tick­led on their chest.

‘It is a stress re­sponse among prey species,’ ex­plains an­i­mal be­haviourist Dr huw stacey. ‘The rab­bit is keep­ing still be­cause it is scared, not be­cause tick­ling is en­joy­able.’

Gar­gale­sis is ex­pe­ri­enced by chimps, go­ril­las and orang­utans, our clos­est pri­mate rel­a­tives. The only other an­i­mal proven to re­spond to this type of tick­ling is, bizarrely, the rat. Neu­ro­sci­en­tist Jaak Panksepp found the ro­dents emit high­pitched noises — a laugh — in re­sponse to be­ing tick­led.

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