  Prior work has explored the writing challenges experienced by people with
dyslexia, and the potential for new spelling, grammar, and word retrieval
technologies to address these challenges. However, the capabilities for natural
language generation demonstrated by the latest class of large language models
(LLMs) highlight an opportunity to explore new forms of human-AI writing
support tools. In this paper, we introduce LaMPost, a prototype email-writing
interface that explores the potential for LLMs to power writing support tools
that address the varied needs of people with dyslexia. LaMPost draws from our
understanding of these needs and introduces novel AI-powered features for
email-writing, including: outlining main ideas, generating a subject line,
suggesting changes, rewriting a selection. We evaluated LaMPost with 19 adults
with dyslexia, identifying many promising routes for further exploration
(including the popularity of the "rewrite" and "subject line" features), but
also finding that the current generation of LLMs may not surpass the accuracy
and quality thresholds required to meet the needs of writers with dyslexia.
Surprisingly, we found that participants' awareness of the AI had no effect on
their perception of the system, nor on their feelings of autonomy, expression,
and self-efficacy when writing emails. Our findings yield further insight into
the benefits and drawbacks of using LLMs as writing support for adults with
dyslexia and provide a foundation to build upon in future research.
