▁when ▁they ▁attempt ▁to ▁recall ▁a ▁word ▁based ▁on ▁a ▁c ue ▁of ▁that ▁word ▁pair . ▁In tr us ions ▁tend ▁to ▁have ▁either ▁semantic ▁attributes ▁in ▁common ▁with ▁the ▁correct ▁word ▁not ▁re called ▁or ▁have ▁been ▁previously ▁studied ▁in ▁another ▁word ▁pair ▁on ▁the ▁current ▁list ▁or ▁a ▁previously ▁studied ▁list ▁or ▁were ▁close ▁in ▁time ▁to ▁the ▁c ue ▁item . ▁When ▁two ▁items ▁are ▁similar , ▁an ▁intr usion ▁may ▁occur . ▁Professor ▁K ah ana ▁and ▁Marie ke ▁V ug t ▁at ▁the ▁University ▁of ▁Pennsylvania ▁exam ined ▁the ▁effects ▁of ▁face ▁similarity ▁for ▁face - name ▁associations . ▁In ▁the ▁first ▁experiment , ▁they ▁wanted ▁to ▁determine ▁if ▁performance ▁of ▁recall ▁would ▁vary ▁with ▁the ▁number ▁of ▁faces ▁in ▁the ▁study ▁set ▁that ▁were ▁similar ▁to ▁the ▁c ue ▁face . ▁F aces ▁were ▁similar ▁if ▁the ▁radius ▁of ▁the ▁faces ▁were ▁within ▁a ▁range . ▁The ▁number ▁of ▁faces ▁within ▁a ▁radius ▁is ▁called ▁a ▁neighborhood ▁density . ▁They ▁found ▁that ▁the ▁recall ▁of ▁a ▁name ▁to ▁face ▁exhib ited ▁a ▁lower ▁accuracy ▁and ▁slower ▁reaction ▁time ▁for ▁faces ▁with ▁a ▁greater ▁neighborhood ▁density . ▁The ▁more ▁similarity ▁that ▁two ▁faces ▁have , ▁the ▁greater ▁the ▁probability ▁for ▁inter ference ▁between ▁the ▁two ▁faces . ▁When ▁cu ed ▁with ▁face ▁A , ▁name ▁B ▁may ▁be ▁re called ▁if ▁face ▁A ▁and ▁B ▁are ▁similar , ▁which ▁would ▁sign ify ▁that ▁an ▁intr usion ▁has ▁occurred . ▁The ▁probability ▁of ▁correct ▁recall ▁came ▁from ▁the