AUTHOR=Lukic Sladjana , Krauska Alexandra , Yoshida Masaya , Thompson Cynthia K. 

TITLE=The role of category ambiguity in normal and impaired lexical processing: can you paint without the paint?

JOURNAL=Frontiers in Human Neuroscience

VOLUME=17

YEAR=2023

URL=https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2023.1028378

DOI=10.3389/fnhum.2023.1028378

ISSN=1662-5161

ABSTRACT=<sec><title>Introduction</title><p>Many words are categorially ambiguous and can be used as a verb (<italic>to paint</italic>) or as a noun (<italic>the paint</italic>) due to the presence of unpronounced morphology or “zero morphology”. On this account, the verb “paint” is derived from the noun “paint” through the addition of a silent category-changing morpheme. Past studies have uncovered the syntactic and semantic properties of these categorially ambiguous words, but no research has been conducted on how people process them during normal or impaired lexical processing. Are these two different uses of “paint” processed in the same way? Does this morphosyntactic structure have an effect on online sentence processing?</p></sec><sec><title>Methods</title><p>This study presents two experiments that investigate the effect of morphosyntactic complexity in categorially ambiguous words presented in isolation (experiment 1) and in a sentential context (experiment 2). The first experiment tested the ability to process categorially unambiguous and ambiguous nouns and verbs in 30 healthy older adults and 12 individuals with aphasia, using a forced choice phrasal-completion task, in which individuals choose whether <italic>the</italic> or <italic>to</italic> is most compatible with target words.</p></sec><sec><title>Results</title><p>Healthy controls and individuals with fluent aphasia all showed: (1) a bias toward the base category in selection rates for <italic>the</italic> and <italic>to</italic>, where <italic>the</italic> was selected more frequently for words identified to be base nouns, and <italic>to</italic> was selected more frequently for base verbs, and (2) longer reaction times for ambiguous (over unambiguous) words. However, individuals with non-fluent agrammatic aphasia showed a base-category effect only for nouns, with chance performance for verbs. The second experiment, using an eye-tracking while reading paradigm with 56 young healthy adults, showed a reading time slowdown for derived forms (<italic>to paint</italic>) compared to their base-category counterparts (<italic>the paint</italic>) in sentence contexts.</p></sec><sec><title>Discussion</title><p>These findings suggest that categorially ambiguous words likely share a common root, and are related by zero-derivation, and that impaired access to the base-category (i.e., verbs like <italic>to visit</italic>) precludes associated morphological processes and therefore the retrieval of the derived-category (i.e., nouns like <italic>the visit</italic>) in non-fluent agrammatic aphasia. This study provides insights into the theory of zero morphology, and the principles that need to be accounted for in models of the lexicon.</p></sec>