Design Features, Acquisition and Language Faculty

Innateness evidence and ape language studies

The innateness hypothesis holds that the human capacity for language is biologically determined and specific to the species, so it is not acquired entirely from experience. Three kinds of evidence are usually cited. First, every human society, however simple, has language, so the capacity is universal. Second, children acquire the language around them without explicit instruction, even from fragmentary and imperfect input. Third, speakers of every language can produce and understand an unbounded number of sentences, which points to a generative system rather than memorized patterns. The fact that languages change over time is a historical observation and does not show that the faculty is innate. Studies of apes such as Washoe, Koko and Sarah showed that these animals could use signs or tokens as arbitrary symbols, could sign with considerable manual skill, could combine signs in new ways, and could teach signs to other chimpanzees. Critics such as Herbert Terrace, however, argued that the multi-sign combinations were largely imitative and did not show rule-governed syntax. The capacity to produce rule-governed, novel messages is therefore the one that these studies did not establish. For example, a chimpanzee that strings together signs it has been taught shows symbolic use, but this alone does not show that it has grammar.

Hockett design features

Charles Hockett listed a set of design features that distinguish human language from other animal communication systems. Among them are arbitrariness, which means that there is no natural link between a form and its meaning; duality of patterning, which means that meaningless sound units combine into meaningful units; productivity, which means that speakers can create an unlimited number of novel utterances; and displacement, which means that language can refer to things that are not present in the immediate time or place of speech. Displacement is the feature that allows speakers to talk about their present, past and future. Students should keep these features distinct, since each names a different property and none of them is a substitute for another. Grammatical structure is part of what makes productivity possible. Every English sentence has a subject and a predicate, although imperatives have an unexpressed subject. Verbs are classified by their argument structure, and intransitive verbs such as 'sleep' or 'sing' take no object. A sentence such as 'The bird sang' therefore has a subject and a verb but no object, complement or adjunct. The claims that every verb must take an object, or that every sentence must contain a subject, an object and a verb, are therefore false.

Indexical vs symbolic communication systems

Signs are classified by the relation between the signal and what it stands for. An iconic sign resembles what it represents. An indexical sign is linked to its referent by a causal or contiguous relation, so that a signal points to the presence or cause of something. An example is a trace left by an animal, which indicates that the animal was there. A symbolic sign is linked to its meaning by an arbitrary, conventional association, as in words. Communication systems are also classified as discrete, when signals fall into distinct categories, or continuous, when signals vary along a graded scale. Footprints on a beach are indexical, since they are traces that indicate a creature has passed, and they are discrete, since each print is a separate unit. Students should identify the type of the sign relation and the discreteness of the signal separately, because a system can be indexical and continuous, or symbolic and discrete. For instance, smoke indicates fire by causal connection, whereas the word 'fire' is symbolic.

Duality of patterning in sign languages

Duality of patterning is the property by which a language combines a small set of meaningless units into a large set of meaningful units. In spoken languages these meaningless units are sounds, and they combine into morphemes and words. Sign languages show the same property. Their meaningless components include handshape, location, movement and palm orientation, and these combine to form meaningful signs in the same way that phonemes combine into words. Sign languages are therefore not simply collections of iconic gestures. Students should be careful with the idea that signs are transparent. Many signs are arbitrary, and deaf children who lack a conventional language still develop shared communicative systems, which shows the human drive toward structured language. For example, a change in handshape alone can change the meaning of a sign, just as a change in one sound can change the meaning of a spoken word.

Overregularization in child acquisition

Overregularization occurs when a child applies a productive grammatical rule to words that are exceptions to it. A child who says 'goed', 'eated', 'runned' or 'knowed' has learned that the regular past tense suffix -ed marks the past, and has extended it to irregular verbs. Such forms are typical of children aged about three, and they are not found in adult speech. They are evidence that the child has acquired the rule and is applying it productively. The same sample of child speech also shows that children use function words such as 'in', 'the', 'for', 'us' and 'these' correctly, which indicates the distinction between lexical and non-lexical categories. Correct forms such as 'him', 'us' and 'my' show that the child has acquired the appropriate case forms. Students should note that a child who overregularizes has not failed to acquire the rule. Instead, the error shows that the rule is in place and that the child has not yet learned the list of exceptions.

Bilingual first language acquisition

A simultaneous bilingual child acquires two languages from birth or early childhood. Research on such children has shown that they often treat both languages as parts of a single system, which is called the unitary language hypothesis. Evidence for this view comes from word formation in which morphemes from the two languages combine within one word, such as a German verb stem with an English progressive suffix. This is not code-mixing in the social sense, which is the use of two languages in a single utterance by speakers who are fluent in both, and it is not code-switching, which is alternation between languages according to conversational context. A mixed language is a stable language that a community develops, and it is not a child's individual pattern. For example, a child who says a word that combines a Hindi root with an English suffix is showing an integrated morphological system.