▁to ▁walk ▁on ▁an ▁elev ated ▁cross ▁which ▁offers ▁both ▁a vers ive ▁and ▁prefer able ▁conditions ▁( in ▁this ▁case , ▁two ▁arms ▁were ▁lit ▁and ▁two ▁were ▁dark ). ▁C ray fish ▁which ▁experienced ▁an ▁electric ▁shock ▁displayed ▁en hanced ▁fear ful ness ▁or ▁anx iety ▁as ▁demonstrated ▁by ▁their ▁preference ▁for ▁the ▁dark ▁arms ▁more ▁than ▁the ▁light . ▁Furthermore , ▁shock ed ▁c ray fish ▁had ▁relatively ▁higher ▁brain ▁ser ot on in ▁concentr ations ▁couple d ▁with ▁elev ated ▁blood ▁gl uc ose , ▁which ▁indicates ▁a ▁stress ▁response . ▁ ▁Moreover , ▁the ▁c ray fish ▁cal med ▁down ▁when ▁they ▁were ▁inject ed ▁with ▁the ▁ben z odia ze pine ▁an xi ol yt ic , ▁ch l ord ia ze po x ide , ▁used ▁to ▁treat ▁anx iety ▁in ▁humans , ▁and ▁they ▁entered ▁the ▁dark ▁as ▁normal . ▁The ▁authors ▁of ▁the ▁study ▁concluded ▁"... str ess - indu ced ▁avoid ance ▁behavior ▁in ▁c ray fish ▁exhib its ▁striking ▁hom ologies ▁with ▁verte br ate ▁anx iety ." ▁ ▁A ▁follow - up ▁study ▁using ▁the ▁same ▁species ▁confirmed ▁the ▁an xi ol yt ic ▁effect ▁of ▁ch l ord ia ze po x ide , ▁but ▁moreover , ▁the ▁intensity ▁of ▁the ▁anx iety - like ▁behaviour ▁was ▁dependent ▁on ▁the ▁intensity ▁of ▁the ▁electric ▁shock ▁until ▁reaching ▁a ▁plate au . ▁Such ▁a ▁quant itative ▁relationship ▁between ▁stress ▁and ▁anx iety ▁is ▁also ▁a ▁very ▁common ▁feature ▁of ▁human ▁and