Tone
Q theory offers new purchase on longstanding problems in the representation of tone. In representing segments as constituents of three subsegments, Q theory is able to represent contour tones both as units (at the segment level) and complex sequences (at the subsegmental level). This enables Q theory to model the autonomous behavior of subsegmental tone features, as Autosegmental Phonology did, while at the same time capturing the behavior of contour tones as units at the segmental level (useful when contour tones undergo assimilation or dissimilates as wholes, in morphophonological operations) (Inkelas & Shih, 2013 [PDF]), (Inkelas & Shih, 2016[PDF]), (Shih, Stephanie & Inkelas, 2014 [PDF]), (Shih & Inkelas, to appear [Prepublication Version]).
Nasal Contours
Additional evidence for a tripartite representation of the segments comes from two Brazilian Languages, Karitiâna (Tupí) and Kaingang (Jê), which possess a contrast in oral and nasal vowels, as well as a series of phonemically nasal consonants /m, n, ɲ, ŋ/. These consonants undergo partial oralization when they occur immediately before or after a phonemically oral vowel. Q-theory can has the representational stregth to capture these contrasts. In Kaingang, phonemically nasal consonants are realized as fully nasal only when they occur adjacent to nasal vowels and/or word boundaries (m m m); as post-oralized when they occur before an oral vowel (m m b); as preoralized when they occur after an oral vowel (b m m); and circumoralized when they occur between two oral vowels (b m b) (Garvin et al. 2018 [PDF]).
Diphthongs
Q-Theory captures the differences in segment strength between simple vowels and diphthongs. By proposing that a monophthong consists of three subsegments, e.g. (a1 a2 a3), but each component of a diphthong – only of two, e.g. (a1 a2 e2 e3), the theory predicts that one vocalic target of a diphthong is weaker (i.e. corresponds to fewer subsegments) than a monophthong. Since each subsegment may be independently subject to faithfulness constraints, diphthongs might show emergence-of-the-unmarked (TETU) effects (McCarthy and Prince, 1994), while monophthongs surface faithfully. This prediction is borne out by A’ingae postlabial rounding.
Geminates
Geminate consonants provide an excellent testing ground for the hypothesis that a phonologically long segment may support a representation with more than three subsegments. Geminates are by definition longer than singletons, though phonetically their duration is typically not double that of singletons. Geminates typically have a similar internal featural structure to their singleton counterparts; the transition into a geminate and the release of that geminate is typically the same as the transitional portions of a singleton. It is characteristically the closure phase of a geminate that is extended durationally and, arguably, ambisyllabic. Q Theory has the descriptive sensitivity to represent both the durational and the articulatory properties of gemination, which is captured by the following representation: (t1 t2 . t2 t3) (Garvin et al. 2018 [PDF]).
Segment Strength
Q Theory's descriptive capability to represent segments with greater than or less than three subsegments offers a more fine-grained and predictive way to capture the differences between vowels of varying phonological statuses -- from excrescent to epenthetic to phonologically long vowels. Making correspondence and markedness constraints stringently sensitive to the number of qs in a segment generates predictions regarding phonological behavior of the vowels. Vowels with fewer subsegments show weaker phonological status and are less likely to display full inventory contrasts, bear stress, head a syllable, or trigger phonological processes. (Inkelas & Shih, 2016[PDF]), (Inkelas & Shih, 2017[PDF]), (Garvin et al. 2018 [PDF]).
