▁rec ency ▁and ▁prim acy ▁effects , ▁or ▁the ▁ph on ological ▁similarity ▁effect . ▁ ▁The ▁Prim acy ▁Model ▁moves ▁away ▁from ▁these ▁two ▁assumptions , ▁suggesting ▁that ▁IS R ▁results ▁from ▁a ▁gradient ▁of ▁activation ▁levels ▁where ▁each ▁item ▁has ▁a ▁particular ▁level ▁of ▁activation ▁that ▁corresponds ▁to ▁its ▁position . ▁Research ▁has ▁supported ▁the ▁fact ▁that ▁immediate ▁serial ▁recall ▁performance ▁is ▁much ▁better ▁when ▁the ▁list ▁is ▁hom ogen ous ▁( of ▁the ▁same ▁semantic ▁category ) ▁than ▁when ▁they ▁are ▁heter ogeneous ▁( of ▁different ▁semantic ▁category ). ▁This ▁suggests ▁that ▁semantic ▁representations ▁are ▁benef icial ▁to ▁immediate ▁serial ▁recall ▁performance . ▁Short - term ▁serial ▁recall ▁is ▁also ▁affected ▁by ▁similar - s ounding ▁items , ▁as ▁recall ▁is ▁lower ▁( rem ember ed ▁more ▁poor ly ) ▁than ▁items ▁that ▁do ▁not ▁sound ▁al ike . ▁This ▁is ▁true ▁when ▁lists ▁are ▁tested ▁independently ▁( when ▁comparing ▁two ▁separate ▁lists ▁of ▁similar - s ounding ▁and ▁not ▁similar - s ounding ▁items ) ▁as ▁well ▁as ▁when ▁tested ▁using ▁a ▁mixed ▁list . ▁Alan ▁Bad de ley ▁first ▁reported ▁such ▁an ▁experiment ▁in ▁which ▁items ▁within ▁a ▁list ▁were ▁either ▁mut ually ▁dis similar ▁or ▁highly ▁similar . ▁ ▁There ▁is ▁evidence ▁indicating ▁that ▁rh ythm ▁is ▁highly ▁sensitive ▁to ▁compet ing ▁motor ▁production . ▁A ctions ▁such ▁as ▁pac ed ▁finger ▁t apping ▁can ▁have ▁an ▁effect ▁on ▁recall ▁as ▁the ▁dis rupt ive ▁impact ▁of ▁pac ed ▁finger ▁t apping , ▁but ▁lack ▁of ▁consistent