Absolute pitch is more common among speakers of tonal languages, such as most dialects of Chinese or Vietnamese, which often depend on pitch variation as the means of distinguishing words that otherwise sound the same—e.g., Mandarin with four possible tonal variations, Cantonese with six, Southern Min with seven or eight (depending on dialect), and Vietnamese with six. Speakers of Sino-Tibetan languages have been reported to speak a word in the same absolute pitch (within a quarter-tone) on different days; it has therefore been suggested that absolute pitch may be acquired by infants when they learn to speak a tonal language (and possibly also by infants when they learn to speak a pitch-accent language). However, the brains of tonal-language speakers do not naturally process musical sound as language; perhaps such speakers are more likely to acquire absolute pitch for musical tones when they later receive musical training. Many native speakers of a tone language, even those with little musical training, are observed to sing a given song consistently with regard to pitch. Among music students of East Asian ethnic heritage, those who speak a tone language fluently have a higher prevalence of absolute pitch than those who do not speak a tone language.