5.1 Language Development
Chomsky and the Poverty of the Stimulus
Chomsky demonstrated that children acquire linguistic rules or grammar without an inexhaustive sample of the acquired language. In other words, children cannot learn the rules of grammar by mere exposure to a language (Chomsky, 1965). For one thing, children hear an imperfect input. Sometimes there are contractions such as gonna and wanna and words are not necessarily separated in continuous speech. There is also a lack of examples of all the grammatical structures in a language for children to derive all linguistic rules from analysing the input. All of these phenomena are often labelled the “poverty of the stimulus” (Berwick, Pietroski, Yankama, & Chomsky, 2011). Poverty of the stimulus is often used as an argument for universal grammar. This is the claim that all languages have some underlying common structure within which all surface structures of language emerge.
Language Development
Language development is perhaps one of the greatest mysteries in psycholinguistics. The rapidity of first language acquisition is astounding to anyone who has tried to learn a second language as an adult. This process can be broadly divided into stages based on the characteristics of the infants’ output. However, we must note that output doesn’t always assure us a clear picture of the cognitive processes that are going on within the infants’ minds.
As seen in Figure 5.1, infants make vegetative sounds from birth. At around 6 weeks, we start getting cooing sounds followed by vocal play between 16 weeks and 6 months (Stark, 1986). This vocal play involves sounds that appear similar to speech but containing no meaning. Babbling is observed between 6 to 9 months. This is different from vocal play in that it contains true syllables (generally CV syllables as in ‘wa wa’ for ‘water’). Children produce single-word utterances around 10 to 11 months followed by an extraordinary expansion of vocabulary around 18 months. At the same time, we start to get two-word utterances. We also start to get telegraphic speech. These are utterances which lack grammatical elements (Brown & Bellugi, 1964). Grammatically complex utterances emerge around two and a half years.
Research methods that we can employ with adults is not always possible with infants. This paradigm measures the rate of sucking an artificial pacifier as a measure of interest by the infant in a novel stimulus. It has been observed that babies prefer novel stimuli as opposed to stimuli that are familiar. If they are presented with habituated (or familiar) stimuli and then a novel stimulus pops up, the rate of sucking increases. This can be used to see whether an infant can detect the difference between who stimuli. Another technique is the preferential looking technique. Here children look longer at scene that are consistent with what they are hearing. Using such techniques (and others), psycholinguists try to determine at what age children understand