SPEECH is the vocalized form of communication used by humans, which is based upon the syntactic combination of items drawn from the lexicon . Each spoken word is created out of the phonetic combination of a limited set of vowel and consonant speech sound units (phonemes ). These vocabularies, the syntax that structures them, and their sets of speech sound units differ, creating many thousands of different, and mutually unintelligible , human languages . The vocal abilities that enable humans to produce speech also enable them to sing .
A gestural form of human communication exists for the deaf in the
form of sign language .
It is controversial how far human speech is unique; in that animals
also communicate with vocalizations. While none in the wild have
compatibly large vocabularies, research upon the nonverbal abilities
of language trained apes such as Washoe and
* 1 Production
* 2 Perception * 3 Repetition * 4 Problems involving speech
* 5.1 The classical model * 5.2 Modern research
* 6 See also * 7 References * 8 Further reading * 9 External links
Speech production is a multi-step process by which thoughts are generated into spoken utterances. Production involves the selection of appropriate words and the appropriate form of those words from the lexicon and morphology, and the organization of those words through the syntax. Then, the phonetic properties of the words are retrieved and the sentence is uttered through the articulations associated with those phonetic properties.
In linguistics (articulatory phonetics ), articulation refers to how
the tongue, lips, jaw, vocal cords, and other speech organs used to
produce sounds 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 . However humans can pronounce words without the use of the lungs and glottis in alaryngeal speech , of which there are three types: esophageal speech , pharyngeal speech and buccal speech (better known as Donald Duck talk ).
Main article: Speech error
Speech production is a complex activity, and as a consequence errors
are common, especially in children.
Main article: Speech perception
Speech perception refers to the processes by which humans can interpret and understand the sounds used in language. The study of speech perception is closely linked to the fields of phonetics and phonology in linguistics and cognitive psychology and perception in psychology. Research in speech perception seeks to understand how listeners recognize speech sounds and use this information to understand spoken language . Research into speech perception also has applications in building computer systems that can recognize speech, as well as improving speech recognition for hearing- and language-impaired listeners.
Speech perception is categorical , in that people put the sounds they hear into categories rather than perceiving them as a spectrum. People are more likely to be able to hear differences in sounds across categorical boundaries than within them. A good example of this is voice onset time (VOT). For example, Hebrew speakers, who distinguish voiced /b/ from voiceless /p/, will more easily detect a change in VOT from -10 ( perceived as /b/ ) to 0 ( perceived as /p/ ) than a change in VOT from +10 to +20, or -10 to -20, despite this being an equally large change on the VOT spectrum.
In speech repetition, speech being heard is quickly turned from sensory input into motor instructions needed for its immediate or delayed vocal imitation (in phonological memory ). This type of mapping plays a key role in enabling children to expand their spoken vocabulary. Masur (1995) found that how often children repeat novel words versus those they already have in their lexicon is related to the size of their lexicon later on, with young children who repeat more novel words having a larger lexicon later in development. Speech repetition could help facilitate the acquisition of this larger lexicon.
PROBLEMS INVOLVING SPEECH
See also: Speech-language pathology
There are several organic and psychological factors that can affect speech. Among these are:
* Diseases and disorders of the lungs or the vocal cords , including
paralysis , respiratory infections (bronchitis), vocal fold nodules
and cancers of the lungs and throat.
* Diseases and disorders of the brain , including alogia , aphasias
, dysarthria , dystonia and speech processing disorders, where
impaired motor planning , nerve transmission, phonological processing
or perception of the message (as opposed to the actual sound) leads to
poor speech production.
* Hearing problems, such as otitis media with effusion , and
listening problems, auditory processing disorders , can lead to
* Articulatory problems, such as slurred speech , stuttering ,
lisping , cleft palate , ataxia , or nerve damage leading to problems
in articulation .
THE CLASSICAL MODEL
Broca's and Wernicke's areas.
The classical or Wernicke-Geschwind model of the language system in the brain focusses 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). In this model, a linguistic auditory signal is first sent from the auditory cortex to Wernicke's area. The lexicon is accessed in Wernicke's area, and these words are sent via the arcuate fasciculus to Broca's area, where morphology, syntax, and instructions for articulation are generated. This is then sent from Broca's area to the motor cortex for articulation.
Paul Broca identified an approximate region of the brain in 1861
which, when damaged in two of his patients, caused severe deficits in
speech production, where his patients were unable to speak beyond a
few monosyllabic words. This deficit, known as Broca's or expressive
aphasia , is characterized by difficulty in speech production where
speech is slow and labored, function words are absent, and syntax is
severely impaired, as in telegraphic speech . In expressive aphasia,
speech comprehension is generally less affected except in the
comprehension of grammatically complex sentences.
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. Instead, multiple streams are involved in speech production and comprehension. 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.
* ^ Levelt, Willem J. M. (1999). "Models of word production".
_Trends in Cognitive Sciences_. 3 (6): 223–232.
* ^ Catford, J.C.; Esling, J.H. (2006). "Articulatory Phonetics".
In Brown, Kieth. _Encyclopedia of