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The abstract auditory rule of speech refers to the abstract and constant relations between speech stimuli, which has currently been under study for its underlying neural mechanisms at an attentive stage.However, it is unknown whether or not the human brain has a capacity of encoding abstract auditory rules of speech at a preattentive stage already.To address this issue, we presented native Chinese speakers continuously with Chinese vowels differing in formant, intensity and level of pitch to construct an auditory input stream, in which most of vowels shared flat lexical tones to form an embedded abstract auditory rule, and occasionally this rule was violated with random occurrence of those with rising or falling lexical tones.With whole-head electrical recordings of the mismatch negativity, we show that the rule violation evoked a robust preattentive auditory response while none of the subjects acquired explicit knowledge of the rule or became aware of the violation of the rule.Our results reveal a sensory intelligence in perception of Chinese lexical tones.Given that Chinese lexical tones are semantically meaningful, our study further indicates the humans capability of unconscious extraction of abstract auditory rules of speech, which may be critical for speech communication in noisy and adversary auditory environments.