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.
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.
Requests for clarification occur when a parent asks a question that can prompt a child to fix an ungrammatical sentence they previously said.
[5] Furthermore, Gary Marcus argues that implicit direct negative evidence in the input is insufficient for children to learn the correct grammar of their language.
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.
[11] However, other researchers have conducted studies that demonstrate that children do not need negative feedback in order to learn language.
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.
Proponents of linguistic nativism suggest that the answer to the "no negative evidence" problem is that language knowledge that cannot be learned is innate.
In an experiment conducted by Fei Xu and Joshua Tenenbaum, 4-year-old participants learning a novel word 'fep' readily decided that it referred only to Dalmatians if only hearing it while shown pictures of Dalmatians; although they received no information that 'fep' was unable to refer to other kinds of dogs, the suspicious coincidence that they had never heard it in other contexts caused them to restrict their meaning to just one breed.
It has been argued that children use indirect negative evidence to make probabilistic inferences about the syntax of the language they are acquiring.
According to Regier and Gahl, young language learners form hypotheses about what is and isn't correct based on probabilistic inferences.
Notably, Regier and Gahl assert that this ability for probabilistic inference can be used in all sorts of general learning tasks, and not just linguistic ones.
In his variational model, Charles Yang notes that based on indirect negative evidence, English-acquiring children could conclude that English is a topic-drop language, such as Chinese.
Yang notes that in English child-directed speech, children very rarely hear expletive subjects.
Yang asserts that this leads English-acquiring children to momentarily conclude that English is a topic-drop language.