From Zeyao Wu:
I am intrigued by how the pronunciation of my nickname changed when I moved to Guangzhou [VHM: in the far south, formerly Canton] from Dongbei [VHM: the Northeast, formerly Manchuria].
In Dongbei, all my relatives and my friends called me Yáoyao 瑶瑶, with the second tone of the second syllable becoming neutral. [VHM: the base tone of yáo 瑶 ("precious jade") is second tone]
When I moved to Guangzhou, my friends call me Yǎoyáo 瑶瑶. It seems that this sort of pronunciation is not standard. I think Cantonese speak in this way because they pronounce Mandarin with the tones of Cantonese.
Here are some other examples (the first column is Pekingese [note the pattern of base tone on the first syllable and neutral tone on the second syllable] and the second column is Guangzhou-style Mandarin [note the pattern of base tone on the first syllable and full base tone on the second syllable, not neutral tone as in Beijing]).
dōngxi | dōngxī 东西 ("thing")
máfan | máfán 麻烦 ("trouble; bother")
shítou | shítóu 石头 ("stone")
yīfu | yīfú 衣服 ("clothing")
Judging from Zeyao's evidence, Cantonese-style Mandarin doesn't favor neutral tone for the second syllable of words. Conversely, northerners, especially Pekingese, seem to favor a very reduced neutral tone on the second syllable of words. When Zeyao said "déxing 德行" ("virtue; virtuous behavior; moral honesty / integrity / conduct; shameful; disgusting" — yes, in Pekingese colloquial, in its most mordant form as a condemnation, déxing 德行 means the exact opposite of its overt signification ["virtuous conduct", etc.]), there was hardly any vocalic quality left to the second syllable at all. So it came out sounding like "désh". I walked up right next to Zeyao and had her say it about five times in front of the whole class, and each time it came out sounding like "désh", with even nary a trace of nasalization. Already over 35 years ago, when I first heard it spoken by Beijing shopgirls, I was intrigued by this Pekingese colloquialism, both for the fact that they used it to convey an antonymous meaning, but also for the very unusual pronunciation. Dripping with vitriol, they would begin quite low in the register for a second tone, and then gradually glide upward — in a haughty, drawn-out way — on the first syllable to a rather high, attenuated pitch, then clip it off with a dismissive sibilant: deeéééé↗sh↓.
Comments by Neil Kubler:
Much of Southern China, also Taiwan, uses the pronunciations cited for Guangzhou. There are at least two reasons for this, I think: (1) Cantonese and Southern Chinese topolects in general don't have nearly so many neutral tones as Mandarin; (2) since Mandarin was learned as a second (foreign, non-native) language by these folks, and typically through character texts — which were often recited by the (typically herself not native) teacher with exaggerated tones, they picked up "reading pronunciations."
However, while I think the preceding is true, I think it's also true that (sadly, from my non-Chinese linguistic perspective), the number of neutral tones in Beijing speech is decreasing. More and more younger Beijing residents are speaking Putonghua rather than Beijinghua, and the emphasis of character texts ("reading pronunciations") is strong there also.
Your student said:
"my friends (in Guangzhou) call me Yǎoyáo 瑶瑶".
In Taiwan also there is a curious phenomenon where some personal names and also kinship terms — like baba, mama, gege, jiejie, didi, meimei — all change from their normal tone patterns (with the 1st syllable one of various tones and the 2nd syllable a neutral tone) to this pattern:
TONE 3 + TONE 2 (just like what your student described for her name in Guangzhou. So "daddy" becomes ba3ba2, and so forth.
I haven't been able to find a satisfactory explanation for why this happens.
Judging from Zeyao's evidence, Cantonese-style Mandarin doesn't favor neutral tone for the second syllable of words. Conversely, northerners, especially Pekingese, seem to favor a very reduced neutral tone on the second / final syllable of words. As I pointed out in my analysis of déxing 德行 ("virtuous / shameful conduct") above, when Zeyao pronounced this word à la Pekingese, there was hardly any vocalic quality left to the second syllable.