Mental lexicon
The mental lexicon is a component of the human language faculty that contains information regarding the composition of words, such as their meanings, pronunciations, and syntactic characteristics.
An individual's mental lexicon changes and grows as new words are learned and is always developing, but there are several competing theories seeking to explain exactly how this occurs.
Recent studies have also shown the possibility that the mental lexicon can shrink as an individual ages, limiting the number of words they can remember and learn.
[14] The middle of the spectrum contains the theories that "suggest that related senses share a general or core semantic representation".
[15] Others work around Chomsky's theory that "all syntactic and semantic features are included directly in the abstract mental representation of a lexical word".
Elman suggests that because context, both linguistic and nonlinguistic, is fundamentally inseparable from language, the human mind should be viewed more holistically when discussing the storage of lexical information.
In Elman's view, this is a more realistic approach than assuming that the mental lexicon stores every minute contextual detail about every single lexical item.
[19] Studies have shown that the temporal and parietal lobes in the left hemisphere are particularly relevant for the processing of lexical items.
[22] Anomia is a lesser level of dysfunction, a severe form of the "tip-of-the-tongue" phenomenon where the brain cannot recall the desired word.
[24][clarification needed] They also have word-retrieval difficulties in spontaneous speech but still have relatively preserved naming of presented stimuli.
[25] The notion of segregated syntactic categories within the mental lexicon is more recently supported by a 2020 article in Cognition, which measured speech onset latency when forty-eight speakers (no specification of speech disorders or lack thereof) were distracted from a target verb or noun with a related verb or a related noun.
[26] However, a 2011 paper in Neuroscience & Biobehavioral Reviews opposes the idea that nouns and verbs are stored separately, instead supporting the point of view that the understanding of nouns and verbs as separate categories arises from semantic and pragmatic notions of objects and actions, respectively, as well as from the learned syntactic environments of the two categories.
In this theory, the mental grammar forms the part of the language faculty that utilizes procedural memory, which is tied to computational tasks and fine motor skills and which is stored in the frontal lobe and basal ganglia.
[28] The lexicon, in turn, is the part that uses declarative memory, which is more strongly oriented towards rote memorization and which is stored in the temporal lobe.
For example, a 2015 study published in Studies in Second Language Acquisition observed that native English speakers placed in an immersive environment (a strategy-based game) for the purpose of acquiring an artificial and deliberately dissimilar to English L2 tended to rely heavily on declarative memory initially even when making syntactic judgements (i.e. completing grammaticality judgement tasks, abbreviated: GJTs).
This study also found that after a slightly longer period of exposure to the artificial L2, some learners would begin to engage their procedural memory in a similar manner as they do in English for syntactic judgements, whereas others would make use of extralinguistic neural circuits for this purpose.
For example, a 2010 study on L1 acquisition of Finnish verbal morphology, which asked monolingual children aged 4–6 to conjugate both real and constructed verbs in the past tense, concluded that the correlation between declarative memory (in the form of vocabulary development) and proficiency at conjugating past-tense verbs was too strong for the declarative/procedural model to be tenable with respect to this level of morphosyntax, given the continued existence of more appropriate models which posit a stronger relationship between lexicon and grammar.
[32] A 2006 study from the University of Massachusetts Amherst concludes that at least phonologically, acronyms are stored as sequences of the names of their constituent letters.
[36] One study showed that the size of a Japanese woman's (referred to as AA) healthy mental lexicon of Kanji shrank at a rate of approximately 1% per year between ages 83 and 93 on average.
Upon the introduction of a more accurate model of learning, it was found that the accuracy of older adults' lexical processing appears to improve continuously over their lifespan, becoming more attuned to the information structure of the lexicon.
[36] It was noted that if investigators simply attended to speed in lexical decision tasks, inevitably evidence of decline will be found.
