The Mental Lexicon
Linguistics is the scientific study of the nature, variation, and structure of language, including the subfields of morphology, syntax, semantics, phonology, lexicology, and pragmatics. The mental lexicon is the language user’s mental dictionary, his knowledge about words and morphemes. Therefore, the mental lexicon is an area of research within the field of lexicology, since lexicology is the study of words, their history and their meaning. Not much is proven about how words are stored and organized in the brain, or how they are accessed, neither in speech production nor in speech perception. However, after having conducted linguistic experiments and having analyzed speech errors, linguists have set up several metaphors and models which can represent the possible structures and processes in the mental lexicon. These metaphors and their genesis will be presented and explained in this essay. Furthermore, although being an area of research within the field of lexicology, it will be shown that the mental lexicon is nevertheless intertwined with all the other subcategories of linguistics.
The mental lexicon is a highly extendable memory: an adult stores around 150.000 words in his brain and is able to use a third of these in everyday life (Aitchison 5-7). Speakers find their words remarkably fast while speaking, and listeners can recognize spoken words within 200 milliseconds, as experiments have shown (Aitchison 8). Therefore, linguists assume that words are not randomly stored on a pile in the brain, but that the mental lexicon is a most organized and systematic structure. A common metaphor used for the organization of the mental lexicon is a dictionary, which implies that words in the brain are listed in alphabetical order, i. e. ordered by orthographical aspects. But this is a controversial subject: if words were stored strictly alphabetically, then we would assume speakers to pick direct neighbors of target words in speech errors. Though analyses of speech errors show that speakers often pick orthographically or phonologically similar words instead of the target words, these wrong words are usually not direct neighbors in an alphabetical list (e.g. using the word periscope instead of stethoscope, Aitchison 11). Furthermore, an order by phonological aspects alone also does not suffice: speakers often substitute target words with semantically similar expressions or their antonyms (e.g. saying leg instead of arm, good instead of bad; Fay/Cutler 507, see also word association experiments in Aitchison 24). Therefore, meaning has to be taken into consideration as well. In addition, 99% of the speech errors agree on the grammatical category of the target word, and 98% on the stress pattern, so grammar and stress seem to be factors for the organization, too (Fay/Cutler 507f.). Furthermore, unlike a dictionary the mental lexicon does not deal with words in isolation and it stores much more information about them than lemmas in dictionaries (e.g. knowledge about different accents and dialects of the target language, possible morphological forms of words, situational use of words; see examples in Aitchison 13-14).