Language Development, Overregulation in

U-Shaped Curve

At some point during language development (around the age of 2 years), children begin acquiring past tense formations. Although they produce both regulars and irregulars more or less accurately in the early stage of past tense acquisition, as they begin to acquire more verbs, they start producing errors, especially with regard to irregular formation. It is at this point during language development when children incorrectly inflect irregular verbs in a regular manner. For example, they may produce * goed instead of went, or * thinked instead of thought (an asterisk indicates ungrammatical forms). This developmental pattern is commonly referred to as a U-shaped learning curve. The irregular past tense forms are said to undergo this U-shaped learning curve because, during early acquisition of the irregular past tense, children produce inflected irregulars correctly. They then go through a phase where they overgeneralize the regular formation in which -ed is simply added to the verb stem. This overregulation of the regular formation to irregular verbs results in irregulars being produced incorrectly. In the final phase of the learning curve, children's performance on irregulars increases as they learn to associate the correct irregular past tense form with its stem.

Explaining Overregulation

It is worth examining why this phenomenon occurs. Recall that the past tense can be inflected regularly or irregularly. In English, many irregular verbs are highly frequent (i.e., they occur quite often). This could explain why the irregular forms are produced accurately at first. However, although individual tokens of irregular verbs are high in frequency, there are many more regular verbs then irregular verbs in English. This difference in type frequency (such as more regular verb types than irregular verb types) may play a role in the overregulation. Therefore, because children come across many more regular verbs than irregular verbs, they overapply the regular rule.

On the other hand, it has also been argued that overregulation occurs because children make use of a grammatical rule (i.e., add -ed to a verb stem), which acts as the default rule. Hence, in cases where no irregular form can be retrieved, the default rule is applied. In German, the regular participle (-t) has a smaller type frequency than the irregular participle (-n) but exhibits overregulation in the same way as the English regular past tense. From this point of view, overregulations are argued to show evidence for symbolic or rule-based representations.

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