▁unknown . ▁Un ambigu ous ▁experimental ▁evidence ▁for ▁the ▁existence ▁of ▁the ▁T ark han ov ▁regular ity ▁in ▁human ▁sexual ▁behaviour ▁has ▁never ▁been ▁obtained . ▁ ▁Another ▁explanation ▁of ▁sexual ▁ar ous al ▁is ▁offered ▁by ▁the ▁approach ▁which ▁Kaz im ierz ▁Im iel i ński ▁calls ▁the ▁" ps ych oh yd ra ul ic ▁model ▁of ▁sexual ity ." ▁This ▁point ▁of ▁view ▁lik ens ▁human ▁sexual ity ▁to ▁a ▁steam ▁bo iler , ▁with ▁bi ological ▁processes ▁or ▁internal ▁ir rit ants ▁creating ▁sexual ▁t ension . ▁If ▁the ▁level ▁of ▁this ▁t ension ▁reaches ▁threshold , ▁sexual ▁ar ous al ▁occurs ▁as ▁the ▁expression ▁of ▁necessity ▁to ▁let ▁off ▁steam . ▁Gary ▁F . ▁Kelly ▁( Cl ark son ▁University ) ▁describes ▁this ▁model ▁as ▁follows : ▁ ▁The ▁" ps ych oh yd ra ul ic ▁model ▁of ▁sexual ity " ▁has ▁been ▁form ulated ▁most ▁definitely ▁in ▁ps y cho analysis : ▁ ▁After ▁a ▁certain ▁time , ▁the ▁same ▁process ▁begins ▁an ew . ▁Such ▁an ▁approach ▁assumes ▁sexual ▁ar ous al ▁to ▁be ▁a ▁sp ont aneous ▁desire ▁that ▁appears ▁period ically ▁like ▁sens ations ▁of ▁hung er ▁and ▁th irst . ▁Draw ing ▁a ▁parallel ▁between ▁these ▁sens ations ▁and ▁sexual ▁exc itation ▁is ▁widely ▁accepted ▁now : ▁" Every one ▁must ▁experience ▁sexual ity ▁in ▁some ▁way ▁to ▁surv ive .   ... ▁In ▁this ▁sense ▁sex ▁is ▁a ▁necessity ▁of ▁life , ▁just ▁as ▁air , ▁food , ▁and ▁warm