Speech

Individuals may also unintentionally communicate aspects of their social position through speech, such as sex, age, place of origin, physiological and mental condition, education, and experiences.

Speech may nevertheless express emotions or desires; people talk to themselves sometimes in acts that are a development of what some psychologists (e.g., Lev Vygotsky) have maintained is the use of silent speech in an interior monologue to vivify and organize cognition, sometimes in the momentary adoption of a dual persona as self addressing self as though addressing another person.

Monkeys, non-human apes and humans, like many other animals, have evolved specialised mechanisms for producing sound for purposes of social communication.

[8][9] The human species' unprecedented use of the tongue, lips and other moveable parts seems to place speech in a quite separate category, making its evolutionary emergence an intriguing theoretical challenge in the eyes of many scholars.

[10] Determining the timeline of human speech evolution is made additionally challenging by the lack of data in the fossil record.

[11] In linguistics, articulatory phonetics is the study of how the tongue, lips, jaw, vocal cords, and other speech organs are used to make sounds.

Normal human speech is pulmonic, produced with pressure from the lungs, which creates phonation in the glottis in the larynx, which is then modified by the vocal tract and mouth into different vowels and consonants.

For example, the fact that children often make the error of over-regularizing the -ed past tense suffix in English (e.g. saying 'singed' instead of 'sang') shows that the regular forms are acquired earlier.

[14][15] Speech errors associated with certain kinds of aphasia have been used to map certain components of speech onto the brain and see the relation between different aspects of production; for example, the difficulty of expressive aphasia patients in producing regular past-tense verbs, but not irregulars like 'sing-sang' has been used to demonstrate that regular inflected forms of a word are not individually stored in the lexicon, but produced from affixation to the base form.

This type of mapping plays a key role in enabling children to expand their spoken vocabulary.

Among these are: Speech and language disorders can also result from stroke,[22] brain injury,[23] hearing loss,[24] developmental delay,[25] a cleft palate,[26] cerebral palsy,[27] or emotional issues.

[29] The classical or Wernicke-Geschwind model of the language system in the brain focuses on Broca's area in the inferior prefrontal cortex, and Wernicke's area in the posterior superior temporal gyrus on the dominant hemisphere of the brain (typically the left hemisphere for language).

[31] Modern models of the neurological systems behind linguistic comprehension and production recognize the importance of Broca's and Wernicke's areas, but are not limited to them nor solely to the left hemisphere.

Damage to the left lateral sulcus has been connected with difficulty in processing and producing morphology and syntax, while lexical access and comprehension of irregular forms (e.g. eat-ate) remain unaffected.