This article discusses currently unsolved problems in linguistics.

Some of the issues below are commonly recognized as problems per se, i.e., it is general agreement that the solution is unknown. Others may be described as controversies, i.e., while there is no common agreement about the answer, there are established schools of thought that believe they have a correct answer.

Languages

• Origin of language is the major unsolved problem, despite centuries of interest in the topic.
• Unclassified languages (languages whose genetic affiliation has not been established, mostly due to lack of reliable data)
  • Special case: Language isolates
• Gradient well-formedness^[1], referring to intermediate linguistic phenomena falling between complete well-formedness and complete ill-formedness.
• Undeciphered writing systems

Psycholinguistics

Main article: Psycholinguistics#Issues and areas of research

• Language emergence:
  • Emergence of grammar^[2]
• Language acquisition:
  • Controversy: infant language acquisition / first language acquisition. How are infants able to learn language- One line of debate is between two points of view: that of psychological nativism, i.e., the language ability is somehow "hardwired" in the human brain, and that of the "tabula rasa" or blank slate, i.e., language is acquired due to brain's interaction with environment. Another formulation of this controversy is "Nature versus nurture".
  • Is the human ability to use syntax based on innate mental structures or is syntactic speech the function of intelligence and interaction with other humans- The question is tightly related with the two major problems: language emergence and language acquisition.
  • The language acquisition device: How localized is language in the brain- Is there a particular area in the brain responsible for the development of language abilities, or is language not localized in the brain, or is it only partially localized-
  • What fundamental reasons explain why ultimate attainment in second language acquisition is typically some way short of the native speaker's ability, with learners varying widely in performance-
  • Animals and language: How much language (e.g. syntax) can animals be taught to use-
• An overall issue: Can we design ethical psycholinguistic experiments to answer the questions above-

Natural language processing

Main article: Natural_language_processing#Major_tasks_in_NLP

• Automatic summarization -
• Foreign language reading aid
• Foreign language writing aid
• Information extraction
• Information retrieval (IR) - IR is concerned with storing, searching and retrieving information. It is a separate field within computer science (closer to databases), but IR relies on some NLP methods (for example, stemming). Some current research and applications seek to bridge the gap between IR and NLP.
• Machine translation - Automatically translating from one human language to another.
• Named entity recognition (NER) - Given a stream of text, determining which items in the text map to proper names, such as people or places. Although in English, named entities are marked with capitalized words, many other languages do not use capitalization to distinguish named entities.
• Natural language generation
• Natural language understanding
• Optical character recognition
• Question answering - Given a human language question, the task of producing a human-language answer. The question may be a closed-ended (such as "What is the capital of Canada-") or open-ended (such as "What is the meaning of life-").
• Speech recognition - Given a sound clip of a person or people speaking, the task of producing a text dictation of the speaker(s). (The opposite of text to speech.)
• Spoken dialogue system
• Text simplification
• Text-to-speech
• Text-proofing
• Garden path sentences

Translation

• Is there an objective gauge for the quality of translation-^[3]
  • Machine translation, despite successes, is a source of a large number of unsolved problems
    • Pronoun resolution, Anaphora (linguistics) ^[4]
    • Nominal compound analysis ^[5]

References

1. ^ Gradient Well-Formedness in Optimality Theory (rtf file):

   "Virtually every generative linguist has had the following experience: a given linguistic entity (sentence, novel word, pronunciation) is presented to a native speaker and judged to be neither fully well-formed nor fully unacceptable. In such instances, consultants often say things like "I guess I could say that," "It's all right but not perfect," "It's pretty bad but not completely out," and the like"

2. ^ "Simulated Evolution of Language: a Review of the Field", Journal of Artificial Societies and Social Simulation vol. 5, no. 2
3. ^ Robert Spence, "A Functional Approach to Translation Studies. New systemic linguistic challenges in empirically informed didactics", 2004, ISBN 3-89825-777-0, thesis. A pdf file
4. ^ Jeffrey C. Reynar, "Topic Segmentation: Algorithms and Applications" (1998), Ph.D thesis, citation.
5. ^ Pierre Isabelle, "Another Look at Nominal Compounds", In Proc. of the 10th International Conference on Computational Linguistics (pdf)