iction ▁ ▁The ▁H KB ▁model ▁states ▁that ▁dynamic ▁inst ability ▁causes ▁switching ▁to ▁occur . ▁H KB ▁measures ▁stability ▁in ▁the ▁following ▁ways : ▁ 1 . <0x09> C rit ical ▁slow ing ▁down . ▁If ▁a ▁perturb ation ▁is ▁applied ▁to ▁a ▁system ▁that ▁takes ▁it ▁away ▁from ▁its ▁station ary ▁state , ▁the ▁time ▁for ▁a ▁system ▁to ▁return ▁to ▁the ▁station ary ▁state ▁( local ▁relax ation ▁time ) ▁is ▁a ▁measure ▁of ▁the ▁system ' s ▁stability . ▁ ▁The ▁less ▁stable ▁the ▁pattern , ▁the ▁longer ▁it ▁should ▁take ▁to ▁return ▁to ▁the ▁established ▁pattern . ▁H KB ▁predict s ▁critical ▁slow ing ▁down . ▁ ▁As ▁the ▁parallel ▁pattern ▁los es ▁stability ▁as ▁frequency ▁is ▁increased , ▁the ▁local ▁relax ation ▁time ▁should ▁increase ▁as ▁the ▁system ▁approaches ▁the ▁critical ▁point . ▁ 2 . <0x09> C rit ical ▁fl uct u ations . ▁If ▁switching ▁patterns ▁of ▁behavior ▁is ▁due ▁to ▁loss ▁of ▁stability , ▁direct ▁measures ▁of ▁fl uct u ations ▁of ▁the ▁order ▁parameter ▁should ▁be ▁detect able ▁as ▁the ▁critical ▁point ▁approaches . ▁ ▁Equ ation ▁ ▁In ▁the ▁H KB ▁model ▁ ϕ ▁is ▁the ▁relative ▁phase ▁or ▁phase ▁relation ▁between ▁the ▁fingers . ▁ ▁The ▁parameter ▁k ▁in ▁the ▁model ▁has ▁a ▁correspond ence ▁to ▁the ▁cycle - to - cycle ▁period ▁of ▁the ▁finger ▁movements , ▁or , ▁the ▁inverse ▁of ▁the ▁movement ▁rate ▁or ▁oscill ation ▁frequency ▁in ▁the ▁experiment . ▁ ▁The ▁equation : ▁▁ ϕ <0xCB>