▁His ▁ 1 9 9 7 ▁article ▁gives ▁an ▁over view ▁of ▁the ▁I - R ▁theory ▁that ▁describes ▁it ▁in ▁terms ▁of ▁five ▁gover ning ▁principles : ▁▁ ▁Reg ist ral ▁direction ▁ ▁Inter v all ic ▁difference ▁ ▁Reg ist ral ▁return ▁ ▁Pro xim ity ▁ ▁Cl os ure ▁▁ 1 . ▁Reg ist ral ▁direction ▁ ▁Small ▁intervals ▁imply ▁continu ation ▁of ▁pitch ▁direction ▁ ▁Lar ge ▁intervals ▁imply ▁a ▁change ▁of ▁direction ▁▁ 2 . ▁Inter v all ic ▁difference ▁ ▁Small ▁intervals ▁imply ▁similar - s ized ▁realized ▁intervals ▁ ▁When ▁the ▁reg ist ral ▁direction ▁changes , ▁a ▁" small " ▁realized ▁interval ▁is ▁defined ▁as ▁the ▁original ▁interval ▁size ▁+ /- ▁ 2 ▁sem it ones ▁ ▁In ▁the ▁absence ▁of ▁direction ▁change , ▁a ▁" small " ▁interval ▁is ▁the ▁original ▁interval ▁+ /- ▁ 3 ▁sem it ones ▁ ▁Lar ge ▁imp lic ative ▁intervals ▁imply ▁smaller ▁realized ▁intervals ▁▁ 3 . ▁Reg ist ral ▁return ▁This ▁is ▁the ▁mel od ic ▁arch et ype ▁ab a ▁or ▁ab a \' ▁where ▁the ▁second ▁tone ▁of ▁a ▁realized ▁interval ▁is ▁very ▁similar ▁to ▁the ▁original ▁pitch ▁( with in ▁ 2 ▁sem it ones ). ▁This ▁arch et ype ▁describes ▁symmetric ▁or ▁near - sym metric ▁patterns ▁such ▁as ▁C - G - C # . ▁Pattern s ▁are ▁less ▁arch et yp ical ▁as ▁they ▁devi ate ▁more ▁from ▁this ▁symmetry . ▁▁ 4 . ▁Pro xim ity ▁ ▁Small ▁realized ▁intervals