This paper provides a frame-based account of the inclusion of non-prototypical members in lexical categorization and semantic classification. It proposes that sense extensions based on metaphorical mappings can be viewed as frame-to-frame transfer, constituting an essential part of our lexical knowledge. Adopting the perspective of frame semantics (Fillmore and Atkins 1991), the study helps delimit and anchors the broad notion of 'domain,' a key concept in defining metaphors, into lexically-attested 'semantic frames' in a principled and systematic manner. Most metaphorical or extended meanings, such as the use of mo 'to touch' in wo mo bu qing ta de yong yi 'I don't understand his intension,' are often neglected by the existing databases. Literally, as a verb of touching, mo is classified as a contact verb, but the above usage of mo clearly indicates its affiliation with cognition verbs. By exploring a number of non-prototypical cognition verbs, kan 'to see', xiu 'to smell', mo, and chi 'to eat', this paper aims to propose a mechanism that allows an effective categorization of non-core members into the appropriate verb class by incorporating and redefining metaphorical extensions in a frame-based approach within the framework of frame semantics. In previous studies of lexical semantics, extended meanings are often excluded from the lexical database. For example, both Levin (1993) and Fillmore, Wooters & Baker (2001) fail to grasp the cognition-related meaning of buy 'to believe' as in I don't buy your story and that of catch 'to understand' in I just can't catch the idea of the book. However, the frequent association of the cognition sense with the two verbs still requires an explanation. In an attempt to account for the usages of various non-prototypical Mandarin cognition verbs, we propose that the usages can be viewed as metaphorical in nature and semantically, the conceptual transfer (cf. Lakoff and Johnson 1980) can be redefined as a partial transfer of frame elements from a source domain/frame to a target domain/frame. For instance, the meaning of kan in [wo/Cognizer] kan kan [yao bu yao bang ta /Issue] 'I am considering whether to help him or not,' belongs to the Cogitating Frame (Target Domain) through an extension from the meaning of kan in [wo/Perceiver] kan kan [zhe zhang zi tiao /Phenomenon] 'I take a look at this note,' in the Perception_active Frame (Source Domain). Through a convergence of frame elements, the key frame element in the Cogitating frame, the Issue, can be viewed as the corresponding frame element in the Perception frame, the Phenomenon. Syntactically, the non-prototypical cognition verb (e.g. kan) displays a similar range of lexical and grammatical collocations in its source domain (as a perception verb) as well as in the target domain (as a cognition verb). Based on lexical aspectual properties, it is shown that Mandarin cognition verbs may encode three different event types, viz. activity achievement and state (cf. Hu 2007). Examples are sorted by the three event types and operated in this paper. With clear operational mechanisms under the framework of frame semantics, metaphorically extended meanings of non-prototypical members can be readily included and well represented in lexical databases and verbal classification. The study ultimately provides a unified account of extended verb members in a grammatically-relevant and semantically-motivated way.