The Withgott effect is a phenomenon in the study of phonology, relating to the pronunciation of stops in American English.
Speakers of American English pronounce the sound [t] in characteristic but complex ways. Many have noted that the words “latter” and “ladder” are nearly homophonous, and such examples once led linguists to characterize t-flapping, where [t] sounds like [d], as occurring between two vowels where the first vowel is stressed (accented). This would correctly rule out a flapped-t in, for instance, “Mathilda” but not “Matty.”
In a dissertation in 1982, M.M. Withgott demonstrated that speakers’ behavior is a good deal subtler in what has come to be known as the Withgott effect. Notably, words seem to be chunked into pronunciation units she referred to as a foot, similar to a metrical unit in poetry. Such chunking was said to block flapping in the word ‘Mediterranean’ ([[Medi[terranean] ], cf. [ [sub[terranean]]). How a word is chunked relates to its morphological derivation, as seen by contrasting morphologically similar pairs such as the following (where the vertical bar shows where Withgott argued there is boundary between neighboring feet):
The medial t in càpitalístic can be flapped as easily as in post-stress cátty [ˈkʰæɾi], in contrast to the medial t in mìlitarístic, which comes at the beginning of a foot, and so must be pronounced as [tʰ], like a t at the beginning of a word.
Long, seemingly monomorphemic words also are chunked in English for purposes of pronunciation. In such words [t]’s — as well as the other unvoiced stops — are pronounced like initial segments whenever they receive secondary stress or are at the beginning of a foot:
Navra tilóva
Abra cadábra
Ala kazám
Rázz matàzz
But:
Fliberti gibety
Humu humu nuku nuku apu a‘a