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Speech production is the process by which thoughts are translated into speech. This includes the selection of words, the organization of relevant grammatical forms, and then the articulation of the resulting sounds by the motor system using the vocal apparatus. Speech production can be spontaneous such as when a person creates the words of a conversation, reactive such as when they name a picture or read aloud a written word, or imitative, such as in speech repetition. Speech production is not the same as language production since language can also be produced manually by signs. In ordinary fluent conversation people pronounce roughly four syllables, ten or twelve phonemes and two to three words out of their vocabulary (that can contain 10 to 100 thousand words) each second. Errors in speech production are relatively rare occurring at a rate of about once in every 900 words in spontaneous speech. Words that are commonly spoken or learned early in life or easily imagined are quicker to say than ones that are rarely said, learnt later in life, or are abstract. Normally speech is created with pulmonary pressure provided by the lungs that generates sound by phonation through the glottis in the larynx that then is modified by the vocal tract into different vowels and consonants. However speech production can occur without the use of the lungs and glottis in alaryngeal speech by using the upper parts of the vocal trait. An example of such alaryngeal speech is Donald Duck talk. The vocal production of speech may be associated with the production of hand gestures that act to enhance the comprehensibility of what is being said. The development of speech production throughout an individual's life starts from an infant's first babble and is transformed into fully developed speech by the age of five.〔Harley, T.A. (2011), Psycholinguistics. (Volume 1). SAGE Publications.〕 The first stage of speech doesn't occur until around age one (holophrastic phase). Between the ages of one and a half and two and a half the the infant can produce short sentences (telegraphic phase). After two and a half years the infant develops systems of lemmas used in speech production. Around four or five the child's lemmas are largely increased, this enhances the child's production of correct speech and they can now produce speech like an adult. An adult now develops speech in four stages: Activation of lexical concepts, select lemmas needed, morphologically and phonologically encode speech, and the word is phonetically encoded.〔Harley, T.A. (2011), Psycholinguistics. (Volume 1). SAGE Publications.〕 ==Three stages== The production of spoken language involves three major levels of processing: conceptualization, formulation, and articulation.〔 The first is the processes of conceptualization or conceptual preparation, in which the intention to create speech links a desired concept to the particular spoken words to be expressed. Here the preverbal intended messages are formulated that specify the concepts to be expressed.〔Levelt, W. (1999). "The neurocognition of language", p.87 -117. Oxford Press〕 The second stage is formulation in which the linguistic form required for the expression of the desired message is created. Formulation includes grammatical encoding, morpho-phonological encoding, and phonetic encoding.〔 Grammatical encoding is the process of selecting the appropriate syntactic word or lemma. The selected lemma then activates the appropriate syntactic frame for the conceptualized message. Morpho-phonological encoding is the process of breaking words down into syllables to be produced in overt speech. Syllabification is dependent on the preceding and proceeding words, for instance: ''I-com-pre-hend'' vs. ''I-com-pre-hen-dit''.〔 The final part of the formulation stage is phonetic encoding. This involves the activation of articulatory gestures dependent on the syllables selected in the morpho-phonological process, creating an articulatory score as the utterance is pieced together and the order of movements of the vocal apparatus is completed.〔 The third stage of speech production is articulation, which is the execution of the articulatory score by the lungs, glottis, larynx, tongue, lips, jaw and other parts of the vocal apparatus resulting in speech.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「speech production」の詳細全文を読む スポンサード リンク
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