Syntax refers to the rules governing the ways words can be combined to create meaningful sentences. Content words are words that provide meaning to the sentence. Language production refers to a number of processes by which we convert thought into language output, in the form of speech, sign language or writing. Social cognition refers to the ways in which people make sense of themselves and of others in order to function effectively in a social world. Speech production proceeds in a top-down manner, also known as conceptually driven.

Language is important for information sharing and promoting social interaction. Language can be used through writing and speech. Mental lexicon is our store of knowledge about words and their uses. Linguistic universals are linguistic features said to be found in all languages. There are several linguistic universals, such as consonants, vowels, negatives, questions and so on. Tonal languages are languages that use changes in tone to alter the meaning of the word, in addition to vowels and consonants. Hockett’s design features for human language consists of a set of properties. Some are shared with animals, but only human language uses the full set. It includes things such as rapid fading, interchangeability and feedback. Functional reference refers to the use by animals of a specific call to stand for a specific object or threat.

Language is a structured system which uses a finite set of sounds to construct words, sentences and conversations. There are several components of language:

1. Phonemes
   Phonemes are the basic sounds that makeup speech within a language. Phones are the basic speech sounds. Phonemes are the smallest meaningful sound unit within a language. Allophones are different phones that are treated as the same phone within a language. The reduction in discrimination between allophones may serve to reduce the ambiguity in the incoming speech signal. Phonotactic rules describe which sounds can go together in a given language.
2. Morphemes
   Morphemes are the meaning units of a language. A free morpheme is a morpheme that can stand alone as a word and a bound morpheme is a morpheme that cannot form a word on its own, but forms a word when attached to a free morpheme. Content words can be changed by adding a morpheme as suffix or prefix (e.g: dependence becomes independence by adding the morpheme prefix ‘in’). Function words provide a grammatical structure that shows how content words relate to each other within a sentence.
3. Semantics and the lexicon
   A word is the smallest unit of grammar that can be meaningfully produced on its own. It can consist of one or more morphemes. Semantics refers to the meaning of words and morphemes and the relationship between the words we use and the object they refer to in the world.
4. Syntax
   The productivity of language refers to the ability to generate novel utterances (e.g: people can create new sentences). Syntax describes the rules that determine the construction of phrases, which is a group of words referring to a particular idea. Slang describes an informal pattern of speech that is considered to be non-standard. Syntax describes descriptive grammar, how language is used and not prescriptive grammar, how language should be used. Sentences follow a hierarchical structure and are made up of the noun phrase and the verb phrase. Recursion refers to the ability to extend sentences infinitely by embedding phrases within sentences (e.g: sentences can become as long as you like as long as the syntax is correct).
5. Discourse
   Discourse refers to multi-sentence speech and includes dialogue, conversation and narrative. Pragmatics refers to the understanding of the communicative function of language and the conventions that govern language use. Linguistic competence is our ability to construct sentences and communicative competence refers to our ability to communicate a message effectively and is driven by social conventions. Conversations are not possible when the participants don’t follow implicit social conventions.

There are strong universals in turn-taking patterns across languages and suggest a common pattern whereby the gaps between turns, and overlaps, are minimized. Grice described four conversation rules or maxims:

1. Maxim of quantity
   The speaker should provide enough information in order to be understood, but not too much information.
2. Maxim of quality
   The speaker should provide accurate information.
3. Maxim of relevance
   The speaker should provide information that is relevant to the current topic of conversation.
4. Maxim of manner
   Ambiguity and vagueness should be avoided.

If the maxims are violated, more cognitive processing is required to determine the response. Violation of the maxims provides the basis of humour (e.g: sarcasm is the violation of the maxim of quality). Connotations refer to the non-literal aspects of word meaning and reflect social and cultural factors that affect the literal processing of word meaning.

Aphasia is the term given to a group of speech disorders that occur following brain injury. Disfluency is hesitation or disruption to the normal fluency of speech. Dysfluency is an abnormal disruption to fluency as a result of brain damage. About 6 in 100 words are affected by disfluency. The use of pauses varies with context, task demands and from individual to individual. A clause is a part of a sentence containing a subject and verb. If people want to find out whether someone is lying, it is better to look at the speech than at other cues.

Parapraxes are slips of the tongue or other actions originally thought to reflect unconscious motives. Errors rarely jump across phrase boundaries. Morpheme exchange mostly happens within clauses. The lexical bias refers to the tendency for phonological speech errors to result in real words. Syntax has a large influence in speech errors, as content words get exchanged with content words, function words with function words and so on.

The tip of the tongue state is a temporary inability to access a word from memory. In the TOT state, the target word is a known word. A feeling-of-knowing is a subjective sense of knowing that we know a word and is an example of meta-memory. Bilinguals produce more cross-language intrusion errors when using their non-dominant language, while very few intrusions occurred when they spoke in the dominant language.

There are a number of stages to speech production:

1. Conceptualization
   The process by which a thought forms and is prepared to be conveyed through language.
2. Formulation of the linguistic plan
   In this stage, the concept or proposition must be translated so that the thought becomes language.
3. Articulation of the plan
   In this stage, the sounds of the word are accesses and the motor program for speech output is planned and articulated.

A lemma is an abstract word form that contains syntactic and semantic information about the word. A lexeme is the basic lexical unit that gives the word’s morpho-phonological properties.

Garret’s model is a serial theory. Serial theories propose that speech production progresses through a series of stages or levels, with different types of processing being completed and each level. According to Garret’s hierarchical model, speech is produced via a series of stages, proceeding in a top-down manner. According to this model, speech production consists of five steps:

1. Conceptual/inferential level
   The meaning to be conveyed is selected
2. Functional level
   Content words are selected and assigned to syntactic roles
3. Positional level
   Content words are placed in order and function words are selected
4. Phonological level
   Speech sounds are selected
5. Articulation level
   Sounds are prepared for speech

This model does not predict errors that occur across levels. Non-plan internal errors occur when the intrusion is external to the planned content of the utterance (e.g: saying something wrong, because you happen to see it right now). Levelt’s model consists of six stages:

1. Conceptual preparation
   The process leading up to the activation of a lexical concept.
2. Lexical selection
   A lemma or abstract word is retrieved from the mental lexicon. All related items are activated.
3. Morphological encoding
   Once the lemma is selected, morphemes are selected. TOT’s can occur here, because the lemma is available, but not yet the phonological form.
4. Phonological coding
   Syllables are computed here.
5. Phonetic encoding
   The sounds are selected.
6. Articulation
   The speech is made ready for output.

There is monitoring until the sixth stage. This model explains errors as the failure of monitoring. Dell’s model uses the concept of spreading activation in a lexical network to show how competing activation across different levels might predict speech errors. Processing is interactive in this model and processing is parallel. There are four levels in Dell’s model: semantic level, a syntactic level, a morphological level and a phonological level. Lexical access involves six steps:

1. Semantic units are activated by an external source.
2. Activation spreads throughout the network
3. The word unit with the highest level of activation if selected and linked to the syntactic frame for the sentence.
4. The phonological information is activated.
5. Activation continues to spread, but phonological units linked to the selected word become more highly activated.
6. The most active phonological units are selected.

Word substitutions occur because a semantically related, but incorrect, choice achieves a higher activation than the target word.

Neurolinguistics is the study of the relationship of brain function to language processing. The lateralization of function refers to the asymmetric representation of a cognitive function in the cerebral hemispheres of humans and higher primates. Language is processed on the left and spatial processing is on the right. When a cognitive function is lateralized, one cortical hemisphere is dominant for that function. The dichotic listening task is one where different stimuli are presented to each ear. There is a right-ear advantage for verbal stimuli. The right hemisphere is involved in the emotional aspects of speech, prosody and aspects of non-literal speech.

The Wernicke-Geschwind model is a simplified model of language function used as the basis for classifying aphasia disorders. It notes a number of key areas for language. The model proposes that we repeat a heard word by processing of the following sequence of brain areas. Following processing of the word in the auditory cortex, information about word meaning is processed in Wernicke’s area and the output is sent to Broca’s area. Broca’s area prepares the speech output and a motor program for output is then articulated via the motor cortex.

Aphasia refers to a language deficit as the result of brain injury. Crossed aphasia refers to language dysfunction following right hemisphere damage in a right-handed individual. Aphasic disorders can be classified according to whether they are fluent, non-fluent or pure. In pure disorders, a particular facet of language is affected, while other language functions remain intact. The fluent disorders are characterized by fluent, but meaningless speech and the non-fluent disorders are characterized by non-fluent, but meaningful speech. There are several types of aphasia:

1. Broca’s aphasia
   This is an acquired language disorder characterized by non-fluent speech, reduced speech output and problems with grammar processing. Patients with Broca’s aphasia often also show telegraphic speech.
2. Global aphasia
   This is an acquired language disorder involving extreme impairment of language function.
3. Non-fluent aphasia
   This is aphasia when the patient’s speech output is reduced, laboured or absent.
4. Wernicke’s aphasia
   This is fluent aphasia, characterized by fluent, but meaningless output and repetition errors.
5. Fluent aphasia
   Aphasia when the patient’s speech is fluent, but not meaningful.
6. Conduction aphasia
   This is aphasia when the patient has a specific difficulty affecting the repetition of speech. This occurs when the connection between Broca’s area and Wernicke’s area is damaged, called the arcuate fasciculus.
7. Anomic aphasia
   This is aphasia when the patient has a specific difficulty with word retrieval. Patients with this know the meaning of words, but seem to experience a TOT state a lot.

Writing requires access to the orthographic form of a word rather than its phonological form. Composition is a process by which ideas are turned into symbols. The Hayes and Flower model of writing proposes a cognitive model of writing that focuses on three main domains affecting the writing process: task environment, long-term memory and the immediate cognitive aspects of the writing process. They also propose three general stages of writing: planning, translating and reviewing.