Errors in early word use

The majority of words that children first learn are often used correctly. However, estimates indicate that up to one-third of the first fifty words that children learn are occasionally misused. Many studies indicate a curvilinear trend in naming errors and mistakes in initial word usage. In other words, early in language acquisition, children rarely make naming errors. However, as vocabulary enhances and language growth accelerates, the frequency of error increases. The amount of error decreases again as vocabulary continues to improve.

Scholars debate the underlying developmental causes and reasons for these mistakes. One theory, the semantic feature hypothesis, states that mistakes occur because children acquire the basic features of a word's meaning before learning its more specific aspects. For instance, the child may initially use the word basketball in reference to any round object, but then change its meaning to a round, orange, and grooved ball that bounces. Children may overextend the meaning of basketball to any round object until they learn the more specific aspects of the word's meaning. Other theories suggest that errors in early word use are the result of an inability on the part of the child to retrieve the correct word. Although the child might have accurately comprehended the word at one time, they are unable to actively retrieve the word or its meaning from their rapidly growing vocabulary.

Overregularization (overgeneralization)

Overregularization is defined as the "application of a principle of regular change to a word that changes irregularly." Examples of overregularization in verb use include using the word comed instead of came. Examples in noun use include using the word tooths instead of teeth. The error is usually seen after children have learned language rules because children apply learned rules to irregular words. Pertaining to the examples, the child using the word comed may have originally used came correctly. Once the child learned the '-ed' suffix rule that commonly forms the past tense; however, the child applied the rule to a verb whose correct grammatical form is irregular. The same applies to the tooths example, but the language rule is the addition of the suffix '-s' to form the plural noun. Overregularization research led by Daniel Slobin argues against B.F. Skinner's view of language development through reinforcement. It shows that children actively construct words' meanings and forms during the child's own development.

Differing views on the causes of overregularization and its extinction have been presented. Gary Marcus et al. published a study in which they monitored the speech of 83 children and recorded the spoken past tense of irregular verbs. They argue that children store irregular verbs in their memory and separately develop a rule for the production of the past tense form of any verb. To correctly use an irregular verb, children must retrieve that verb from their memory and block the rule; however, children's retrieval is often imperfect. They conclude the cause of overregularization with: "When retrieval fails, the rule is applied, and overregularization results." Their study's results found overregularization to be rare with a mean of 2.5% of the spoken irregular verbs, to be used for most irregular verbs from the ages of 2 years old until school ages, to be used less often with the irregular verbs that the child's parents speak more often, and to follow a pattern of "U-Shaped Development" in which the child uses the correct form of the irregular verb before overregularizing it. According to Marcus, overregularization ends when the child develops sufficiently strong memory traces to irregular forms.

Michael Maratsos disagrees with Marcus's causal claim. He argues that the overregularized verb form and the correct irregular form compete for usage, as "the two forms are both initially acceptable alternatives." The child increasingly chooses the irregular form, beating the overregularized one, because the child only experiences the irregular form. Maratsos argues that because children often use both the irregular and overregularized forms of the same verb, even in the same speech sample, the blocking theory proposed by Marcus proves problematic. If retrieval blocks the rule, it is unlikely that the rule would be 'un-blocked' soon after. He argues it seems more likely that environmental input and learning accounts for the gradual decline in overregularization. Moreover, the competition theory accounts for the highly varied rates of overregularization seen in Roger Brown's longitudinal study of Adam, Abe, and Sarah. Abe had an extremely high rate of overregularization, 24%, compared with Adam's rate of 3.6%, and Sarah's of 7.9%. Maratsos claims Abe was intellectually gifted, "likely the best overall learner and retriever of words." If Abe retrieved words well, then having such a high rate of overregularization is incompatible with Marcus's theory, which holds retrieval failure responsible for overregularization. Rather, Abe's bigger vocabulary exposed him to more regular words, resulting in a stronger competition between the irregular and overregularized forms and a higher potential rate of failure.