▁dogs ▁of ▁ 1 6 4 ▁different ▁bre eds ). ▁Five ▁consistent ▁and ▁stable ▁" n arrow ▁tra its " ▁were ▁identified , ▁described ▁as ▁play ful ness , ▁curiosity / f ear less ness , ▁ch ase - pr on eness , ▁soci ability ▁and ▁ag gress iveness . ▁A ▁further ▁higher ▁order ▁axis ▁for ▁sh yn ess – bold ness ▁was ▁also ▁identified . ▁ ▁D ogs ▁presented ▁with ▁images ▁of ▁either ▁human ▁or ▁dog ▁faces ▁with ▁different ▁emot ional ▁states ▁( h appy / play ful ▁or ▁angry / ag gress ive ) ▁pa ired ▁with ▁a ▁single ▁vocal ization ▁( vo ices ▁or ▁b arks ) ▁from ▁the ▁same ▁individual ▁with ▁either ▁a ▁positive ▁or ▁negative ▁emot ional ▁state ▁or ▁brown ▁noise . ▁ ▁D ogs ▁look ▁longer ▁at ▁the ▁face ▁whose ▁expression ▁is ▁con gru ent ▁to ▁the ▁emot ional ▁state ▁of ▁the ▁vocal ization , ▁for ▁both ▁other ▁dogs ▁and ▁humans . ▁ ▁This ▁is ▁an ▁ability ▁previously ▁known ▁only ▁in ▁humans . ▁The ▁behavior ▁of ▁a ▁dog ▁can ▁not ▁always ▁be ▁an ▁indic ation ▁of ▁its ▁friend lin ess . ▁This ▁is ▁because ▁when ▁a ▁dog ▁w ags ▁its ▁tail , ▁most ▁people ▁interpret ▁this ▁as ▁the ▁dog ▁express ing ▁happiness ▁and ▁friend lin ess . ▁Though ▁indeed ▁tail ▁w ag ging ▁can ▁express ▁these ▁positive ▁emot ions , ▁tail ▁w ag ging ▁is ▁also ▁an ▁indic ation ▁of ▁fear , ▁in security , ▁challeng ing ▁of ▁domin ance , ▁establish ing ▁social ▁relationships ▁or ▁a