Have there been any studies done on say Mandarin native speakers who learn as adults other languages which have more lexical tones or which have lexical tones different to Mandarin?
I believe for instance that Mandarin has fewer or simpler tones than Cantonese, Thai, and Vietnamese.
Do we know if such second language learners typically have ease or difficulty acquiring these extra lexical tones compared to a learner whose native language entirely lacks lexical tone?
I found this article, which states that Mandarin Chinese natives and English natives when trained on recognizing lexical tones advanced about equally fast in their training but found different tones to be among the most difficult. Abstract below.
Two groups of listeners, one of native speakers of a tone language (Mandarin Chinese) and one of native speakers of a non-tone language (English) were trained to recognize Cantonese lexical tones. Performance before and after training was measured using closed response-set identification and pairwise difference rating tasks. Difference ratings were submitted to multidimensional scaling (MDS) analyses to investigate training-related changes in listeners’ perceptual space. Both groups showed comparable initial performance and significant improvement in tone identification following training. However, the two groups differed in terms of the tones they found most difficult to identify, and in terms of the tones that were learned best. Differences between the two groups’ training-induced changes in identification (confusions) and perceptual spaces demonstrated that listeners’ native language experience with intonational as well as tone categories affects the perception and acquisition of non-native suprasegmental categories.
I would not separate lexical tone here. There are many other lexical tools. Depending on your native and studied languages, you will (or will not) be able to hear when these tools are used and use it by yourself. Here are some examples:
t͡s, t͡ɕ or retroflex ɻ as they exist in Russian (to a certain proximity). At the same time, English speaker will have difficulties with them.ɯ and short u, but have no issue reproducing ɤ. Things are totally opposite for Russian speakers.The answer is common for all mentioned linguistic phenomenons.
Think if someone is telling a native English speaker about a language that has five more vowels: ɯ, ɤ, etc. — what would they answer? "Yes, other vowels do exist, so what?" They wouldn't be surprised there are languages with vowels. :) This is why it's important to learn many languages: the more you are aware of (not necessarily speaking fluently), the more tools you know and can use.
Let's get back to tones.
I have several Chinese friends who study Thai. Existence of lexical tones is something obvious for them. Since Thai has extra tones, comparing to Mandarin (namely, low and middle tones; plus, Mandarin high corresponds to Thai high-rising), those extra tones make some trouble to hear and reproduce for Chinese speakers, but no more than diphthongs or long/short vowels do, for example.
Also, several Thai friends of mine have studied Mandarin, one is a professional Thai-Mandarin translator. Being curious, I asked them about their study. They have never complained on Chinese lexical tones. What really makes them trouble is Mandarin consonants.
Personally, I have started with Mandarin Chinese, but then stopped my study for years. When it came to learning Thai, yes, my prior familiarity with Chinese tones helped me to skip several lessons of spoken Thai training. I would not say it was critical, however.
Update. One more thing, it seems to be related.
This observation came to me when I was listening to Chinese and Thai songs. Compare:
Chinese speakers tend to minimize phonetic distance between the tones. No, I don't say they ignore it. They only emphasize tones when needed (e.g., the context allows a different word pronounced in another tone).
Thai is the opposite. Native speakers highlight the tones pretty accurately.
Every language has some tones. The question is, to which degree they are relevant to a given language. Even Finnish language, which conventionally 'has no tones', actually marks the first stressed syllable with a falling tone, although there are no 'syntax tones', like in Russian.
I can distinguish Russian rising or falling tones (which are important for conversational syntax) and Spanish or Italian tonic stresses, and I can distinguish both tones for Swedish lexemes (which are either falling or falling-rising), but I cannot distinguish none of two tones in Lithuanian or, say, Tibetan. All these languages have 'common' tones, that is, the tones are distiguished by a universal tone scale.
On the other hand, I relatively easy distinguish four tones in Mandarin, but I cannot distinguish any of three Yoruba tones, perhaps because Yoruba, like Kpelle, is a language with 'private' and not 'common' tones.
