本研究之目的為探究時貌情態範疇之語形和其功能之間如何展現一種自然、非任意性的關係，主要以達悟語之時貌情態構詞法之間的互動關係為證據，檢測Bybee (1985) 所提出的iconicity 假設是否能合理解釋構詞法之形義相似關係。此項假設認為構詞法中語素和語素之
間的結合方式、先後次序和遠近關係不是任意的﹕凡是影響語根之語意變化最直接、最全面的語意範疇，在距離上一定最接近語根，相反的，影響語根之詞彙語意變化最小的語意範疇則遠離語根，所以衍生詞綴距離語根較近，而屈折詞綴距離語根較遠。同樣的，這些語意範疇也會依照對於語根之影響度大小，呈現出與語根溶合之不同緊密程度。
結果顯示達悟語之功能範疇與語根之間的關係雖然大致符合Bybee 的假設﹕表達及物性關係（亦即焦點）的詞綴最接近語根，其次為動貌、最外緣者為情態，然而Bybee 對於這些範疇的定義確不能完全適用於分析達悟語和一般菲律賓語言，因為在達悟語的動詞變化系統中，及物性關係和時貌情態詞綴緊密互動，所以在檢視詞綴與語根之距離關係時，無法將衍生詞綴與屈折詞綴完全分開，所以表達完成和未完成貌之焦點詞綴為“衍生＂詞綴，而表達祈使和虛擬之焦點詞綴為“屈折＂詞綴。

This study aims to investigate the relationships between the forms and functions of the Tense-Aspect-Modality categories. Bybee’s hypothesis (1985) was tested against Yami data to discover how the categories of tense, aspect, and mood interact to support the iconicity hypothesis. The morphemic order and the degree of fusion are not arbitrary, in that the categories that most affect the meanings of the stems occur closest to the stem, whereas those that have least impact on the lexical meaning of the stem occur in the periphery. Greater semantic cohesion of concepts is reflected in a higher degree of fusion in their corresponding expression units.
It was found that although the order of the functional categories follows Bybee’s iconicity principle, in that the valence affix is closest to the stem, while the aspect and modality markers are in the periphery, Bybee’s definition of terms is not entirely true of Yami and Philippine-type languages in general because there is a mixture of derivation and inflection in the Yami verbal system. The indicative focus affixes are
‘derivational’, but the non-indicative affixes are ‘inflectional’.