▁The ▁only ▁way ▁to ▁recall ▁the ▁feelings ▁they ▁had ▁were ▁when ▁sir ens ▁of ▁police ▁vehicles , ▁fire ▁tr uck s , ▁and ▁amb ul ances ▁drove ▁by ▁their ▁house ▁they ▁feel ▁the ▁exact ▁feelings ▁that ▁were ▁in ▁effect ▁on ▁that ▁day . ▁▁ <0x09> Rec all ▁memory ▁is ▁active ▁when ▁a ▁familiar ▁sound ▁triggers ▁a ▁feeling ▁of ▁pain ▁from ▁a ▁past ▁event , ▁but ▁most ▁of ▁the ▁recall ▁is ▁shut ▁out ▁from ▁tra um atic ▁event . ▁It ▁is ▁similar ▁to ▁classical ▁condition ing , ▁when ▁a ▁dog ▁he ars ▁a ▁bell ▁it ▁begins ▁to ▁react ▁to ▁the ▁noise ▁rather ▁than ▁an ▁exterior ▁variable ▁like ▁food ▁or ▁an ▁electric ▁shock . ▁The ▁use ▁of ▁ther apy ▁is ▁constructed ▁for ▁a ▁person ▁with ▁this ▁problem ▁to ▁help ▁avoid ▁the ▁fear ▁associated ▁with ▁sounds ▁or ▁objects , ▁and ▁be ▁able ▁to ▁then ▁recall ▁other ▁pieces ▁of ▁information ▁that ▁happened ▁during ▁the ▁event . ▁ ▁Ph en omena ▁The ▁phenomen ological ▁account ▁of ▁recall ▁is ▁referred ▁to ▁as ▁met ac ogn ition , ▁or ▁" know ing ▁about ▁knowing ". ▁This ▁includes ▁many ▁states ▁of ▁conscious ▁aw aren ess ▁known ▁as ▁feeling - of - know ing ▁states , ▁such ▁as ▁the ▁tip - of - the - t ong ue ▁state . ▁It ▁has ▁been ▁suggested ▁that ▁met ac ogn ition ▁serves ▁a ▁self - reg ul atory ▁purpose ▁where by ▁the ▁brain ▁can ▁observe ▁errors ▁in ▁processing ▁and ▁act ively ▁dev ote ▁resources ▁to ▁resol ving ▁the ▁problem . ▁It ▁is ▁considered ▁an