is there voicing assimilation in English?, compare the behaviour of obstruent clusters with respect to voicing in voicing languages (like Hungarian, Spanish, Russian, etc.) vs. aspirating languages (like English)
neutralization in phonology, does complete neutralization exist?, neutralization phenomena (flapping, stops after fortis fricatives, vowel reduction, nasal place assimilation in English, voicing assimilation in Hungarian, etc.), the role of speech perception in potentially neutralizing positions
the role of Voice Onset Time in the laryngeal contrast of obstruents; the role of phonetic features other than vocal fold vibration in the contrast of obstruents (vowel duration, consonant duration, glottalization, release, etc.)
the laryngeal contrast of fortis vs lenis fricatives and affricates in English, what is their contrast based on?
phonological and non-phonological (social, stylistic, dialectal, frequency, etc.) factors in phonological variation (e.g., glottalization, glottalling, flapping, Linking/Intrusive R, the distribution of /j/, etc.)
different theoretical approaches to the analysis of Linking and Intrusive R (rule-based theories vs. phonetics-based vs. historical approaches vs. analogy-based analyses, etc.)
variation in the realizations of CUBE vowels, when are the diphthongs pronounced long (without glides), when are the long monophthongs (R-vowels) realized as long vs. diphthongized; phonological and nonphonological factors in broadening, smoothing, breaking, unbreaking