In language acquisition, negative evidence is information concerning what is not possible in a language. Importantly, negative evidence does not show what is grammatical; that is positive evidence. In theory, negative evidence would help eliminate ungrammatical constructions by revealing what is not grammatical.
Direct negative evidence refers to comments made by an adult language-user in response to a learner's ungrammatical utterance. Indirect negative evidence refers to the absence of ungrammatical sentences in the language that the child is exposed to.
There is debate among linguists and psychologists about whether negative evidence can help children determine the grammar of their language. Negative evidence, if it is used, could help children rule out ungrammatical constructions in their language.
Direct negative evidence Direct negative evidence in language acquisition consists of utterances that indicate whether a construction in a language is ungrammatical. Direct negative evidence differs from indirect negative evidence because it is explicitly presented to a language learner (e.g. a child might be corrected by a parent). Direct negative evidence can be further divided into explicit and implicit forms.
On the other hand, indirect negative evidence is used to determine ungrammatical constructions in a language by noticing the absence of such constructions.
Explicit direct negative evidence A corpus study found that explicit negative evidence was "very rare", and concluded that because parents do not reliably correct their children's grammatical errors, explicit negative evidence does not facilitate language learning.Brown, R., & Hanlon, C. (1970). Derivational complexity and order of acquisition on child speech. In J. Hayes (Ed.), Cognition and the development of language (pp. 11-53). New York: Wiley. Psychologist David McNeill argues that when parents correct children explicitly, the correction is unlikely to be helpful in learning grammar because it is a single correction that will most likely not be repeated, and therefore a child might not remember or even notice the correction. This is demonstrated in the following exchange between a parent and child, which McNeill recorded:Child: Nobody don't like me. Mother: No, say, "nobody likes me." Child: Nobody don't like me. [This exchange is repeated several times] Mother: No, now listen carefully. Say, "Nobody likes me." Child: Oh! Nobody don't likes me.McNeill, D. (1966) Developmental Psycholinguistics. in The Genesis of Language, F. Smith and G. Miller (eds). MIT Press.As this conversation reveals, children are seemingly unable to detect differences between their ungrammatical sentences and the grammatical sentences that their parents produce. Therefore, children typically cannot use explicit negative evidence to learn that an aspect of grammar, such as using double negatives in English, is ungrammatical. This example also shows that children can make incorrect generalizations about which grammatical principle a parent corrects, suggesting that there must be something other than explicit feedback which drives children to arrive at a correct grammar.
Implicit direct negative evidence In the input Implicit direct negative evidence occurs when a parent responds to a child's ungrammatical utterance in a way that indicates that the utterance was not grammatical. This differs from explicit direct negative evidence because the parent merely implies that the child's utterance is ungrammatical, while explicit direct negative evidence involves a parent unambiguously telling a child that a sentence they produced is ungrammatical. There are several types of implicit direct negative evidence which parents utilize in responses to children's ungrammatical utterances. These forms include: repetitions, recasts, expansions, and requests for clarification. Repetitions occur when a parent repeats a child's utterance word for word, whereas recasts occur when a parent repeats a child's utterance while correcting the ungrammatical part of the sentence. Expansions are similar to recasts because they are potentially corrective utterances, but in expansions a parent also will lengthen the child's original utterance. Requests for clarification occur when a parent asks a question that can prompt a child to fix an ungrammatical sentence they previously said. Generally speaking, there is consensus that implicit direct negative evidence exists in the input, though there is debate about whether children can use implicit direct negative evidence to learn the grammar of their language. It is argued that parents frequently reformulate children's ungrammatical utterances.
Utility Some types of implicit direct negative evidence, such as reformulations, occur regularly in the input, thus making them potentially usable forms of evidence for language acquisition.Snow, C.E.; Ferguson, C. A., eds. (1977). Talking to Children: language input and acquisition. Cambridge Press. Some studies have demonstrated that parents respond differently when children utter grammatical or ungrammatical utterances, which suggests that children can use this parental feedback to learn grammar. Some evidence also supports the hypothesis that children actually use implicit direct negative evidence in practice (see section below).
Though there have been a number of studies that support the hypothesis that children can use implicit direct negative evidence that exists in the input, there have also been studies which stand in stark contrast to this hypothesis.Rhode, Douglas L.T.; Plaut, David C. (Spring 1999). "Language acquisition in the absence of explicit negative evidence: how important is starting small?" (PDF). Cognition. 72: 67–109 Linguists who do not believe that implicit direct negative evidence is helpful for a language learner argue that studies supporting the utility of implicit direct negative evidence do not properly specify which types of utterances qualify as recasts. They criticize the fact that some types of implicit direct negative evidence are not necessarily corrective (i.e. parental responses that may qualify as implicit direct negative evidence can occur after either grammatical or ungrammatical utterances). Additionally, some of these linguists question how children would know to only pay attention to certain kinds of recasts and not others.
Furthermore, Gary Marcus argues that implicit direct negative evidence in the input is insufficient for children to learn the correct grammar of their language. He asserts that negative evidence does not explain why sentences are ungrammatical, thus making it difficult for children to learn why these sentences should be excluded from their grammar. He also argues that for children to be able to even use implicit direct negative evidence, they would need to receive negative feedback on a sentence 85 times in order to eliminate it from their vocabulary, but children do not repeat ungrammatical sentences nearly that often. Marcus also purports that implicit evidence is largely unavailable because the feedback differs from parent to parent, and is inconsistent in both the frequency with which it is offered and the kinds of errors it corrects. Other studies demonstrate that implicit negative evidence decreases over time, so that as children get older there is less feedback, making it less available and, consequentially, less likely to account for children's unlearning of grammatical errors.
Usage Assuming that implicit direct negative evidence is usable, there are some studies which demonstrate that children do use implicit direct negative evidence to correct their grammatical mistakes. For example, experiments show that children produce a greater number of grammatical sentences when parents provide them with any type of immediate implicit direct negative evidence, including recasts. This evidence supports claims that direct negative evidence assists a child in their language learning. Chouinard also found that children are highly attentive to parental responses and that children respond to implicit correction in predictable ways. Children tend to directly respond to these reformulations by either affirming the reformulation or disagreeing with their parent if the parent misunderstood the child's intended meaning, revealing that children can discern when parental feedback is meant to correct their grammatical errors. Additionally, children have been shown to correct their initial errors when a parent recasts the child's morphological error.
However, other researchers have conducted studies that demonstrate that children do not need negative feedback in order to learn language. This is evidenced in a case study in which a mute child was tested to see whether he could comprehend a grammar even though he had received no corrective feedback (since corrective feedback occurs as a response to ungrammatical sentences that children produce). Though the child did not produce any speech and therefore did not receive any negative feedback, researchers found that he was able to learn grammatical rules. Although this study does not answer whether negative evidence can be helpful for learning language, it does suggest that direct negative evidence is not needed to learn grammar. Another study also demonstrates that implicit negative evidence is a negative predictor of the rate at which children eliminated ungrammatical utterances from their speech.
Direct negative evidence in language learning Though there is no consensus regarding whether there is sufficient and usable implicit negative evidence in the input, if children are exposed to direct negative evidence, then they could use that evidence to validate hypotheses they have made about their grammar. On the other hand, if there is not sufficient usable negative evidence in the input, then there is a "no negative evidence" problem, which questions of how a language learner can learn language without negative evidence. This is a problem because if a child only hears grammatical sentences which are consistent with multiple grammars, then it would be impossible to determine which grammar is correct unless there was some other factor influencing what grammar a child ultimately hypothesizes to be correct.
Proponents of linguistic nativism suggest that the answer to the "no negative evidence" problem is that language knowledge that cannot be learned is innate. They argue that the language input is not rich enough for children to develop a fully developed grammar from the input alone. This view is referred to as the poverty of the stimulus argument. The central idea of the poverty of the stimulus argument is that children could have multiple hypotheses about aspects of their grammar which are distinguishable only by negative evidence (or by hearing ungrammatical sentences and recognizing those sentences as ungrammatical). Supporters of the poverty of the stimulus argument assert that because the negative evidence that is needed to learn language by the input alone does not exist, children cannot learn certain aspects of grammar from the input alone, and therefore there must be some aspects of grammar which involve innate mechanisms.Lasnik, Howard; Lidz, Jeffrey L. (2016-12-22). The Argument from the Poverty of the Stimulus.
Indirect negative evidence in language acquisition