▁by ▁O at ley ▁and ▁Jenkins ▁who ▁see ▁emot ions ▁as ▁having ▁three ▁stages : ▁( i ) ▁app rais al ▁in ▁which ▁there ▁is ▁a ▁conscious ▁or ▁un cons cious ▁evaluation ▁of ▁an ▁event ▁as ▁relevant ▁to ▁a ▁particular ▁goal . ▁An ▁em otion ▁is ▁positive ▁when ▁that ▁goal ▁is ▁advanced ▁and ▁negative ▁when ▁it ▁is ▁imp eded ▁( ii ) ▁action ▁read iness ▁where ▁the ▁em otion ▁gives ▁priority ▁to ▁one ▁or ▁a ▁few ▁kinds ▁of ▁action ▁and ▁may ▁give ▁ur gency ▁to ▁one ▁so ▁that ▁it ▁can ▁interrupt ▁or ▁comp ete ▁with ▁others ▁and ▁( iii ) ▁phys i ological ▁changes , ▁fa cial ▁expression ▁and ▁then ▁behaviour al ▁action . ▁ ▁The ▁structure , ▁however , ▁may ▁be ▁too ▁broad ▁and ▁could ▁be ▁used ▁to ▁include ▁all ▁the ▁animal ▁kingdom ▁as ▁well ▁as ▁some ▁plants . ▁ ▁Mechan istic ▁The ▁second ▁approach , ▁mechan istic , ▁requires ▁an ▁exam ination ▁of ▁the ▁mechan isms ▁that ▁drive ▁emot ions ▁and ▁search ▁for ▁similar ities ▁in ▁animals . ▁ ▁The ▁mechan istic ▁approach ▁is ▁util ized ▁extens ively ▁by ▁Paul , ▁Hard ing ▁and ▁M endl . ▁Rec ogn izing ▁the ▁difficulty ▁in ▁studying ▁em otion ▁in ▁non - ver bal ▁animals , ▁Paul ▁et ▁al . ▁demonstrate ▁possible ▁ways ▁to ▁better ▁examine ▁this . ▁Ob ser ving ▁the ▁mechan isms ▁that ▁function ▁in ▁human ▁em otion ▁expression , ▁Paul ▁et ▁al . ▁suggest ▁that ▁concentration ▁on ▁similar ▁mechan isms ▁in ▁animals ▁can ▁provide ▁clear ▁ins ights ▁into ▁the ▁animal ▁experience