About

Michele Diaz is a faculty member in the Linguistics Program at Pennsylvania State University. Her research focuses on the neural and cognitive mechanisms that support language, including the role of the right hemisphere in language processing. She is also interested in age-related differences in language. Her work is associated with the Language and Aging Lab, and she is involved in teaching undergraduate courses related to linguistics and language science.

Research topics

• Natural Language Processing
• Computer Science
• Cognitive psychology
• Cognitive science
• Linguistics
• Psychology

Selected publications

• Age-related differences in speech production: Evidence from graph analyses

  2026-04-04

  articleOpen accessSenior author

  Storytelling is a vital aspect of language processing requiring successful integration of characters, events, and actions. Cohesive stories include the necessary information to transition between utterances and convey the overall gist. Although older adults produce more off-topic speech, it remains unclear how age affects narrative organization across discourse contexts. Additionally, broader cognitive declines in aging, like differences in executive function, may contribute to discourse production. The present study examined discourse production using computational speech graph analyses in 268 healthy adults aged 20-81 years old. Participants completed two speech production tasks differing in contextual support: a picture book description and an open-ended prompt. Speech graphs quantified connectedness by modeling words as nodes and their sequential relationships as edges, capturing local repetition and longer-range integration within discourse. Results indicated that age was correlated with increased repetition and less connected speech. There was also a main effect of task where the picture book task elicited denser, more interconnected speech with greater reintegration across the narrative, while the open-ended prompt elicited speech that advanced more sequentially, with fewer cycles linking earlier and later portions of the narrative. Critically, age-related differences in connectedness were most evident in the open-ended prompt and were independent of executive function, suggesting a gradual shift toward more locally constrained speech in later adulthood, particularly when speech must be generated and organized without external support. Importantly, graph-based measures were sensitive to these subtle organizational shifts, highlighting their potential to complement established discourse metrics and deepen our understanding of speech across adulthood.

  PublisherDOI

• Reduced age differences in semantic memory networks: Evidence from semantically diverse free associations

  Neuropsychologia · 2025-11-21

  articleSenior authorCorresponding
  PublisherDOI

• Age-Related Differences in Speech Production and Resting State Functional Network Dynamics

  Neurobiology of Language · 2025-10-02

  articleOpen accessSenior author

  Age-related declines in cognitive function are often accompanied by changes in brain activity and network organization. This study investigated the relationship between resting state brain activity and age-related differences in speech production. We hypothesized that older adults would exhibit altered functional connectivity and activation intensity, correlating with reduced speech quality. Resting state functional MRI data were collected and a composite measure of speech complexity and fluency was calculated from younger and older adults. Results revealed significantly worse speech performance in older adults, accompanied by less segregated whole-brain networks, reduced amplitude of low-frequency fluctuations, and more heterogeneous brain states. Univariate regression analyses indicated stronger brain-behavior relationships in younger adults, while multivariate regression analyses revealed that age-related differences in resting state brain state patterns critically relate to speech production differences. Notably, the language network remained relatively stable with age, whereas whole-brain status became very important for speech performance in older adults. These findings suggest that resting state brain activity, particularly whole brain network characteristics, may serve as a stable biomarker of age-related changes in speech production.

  PublisherOA PDFDOI

• Phonological networks remain intact in multiple sclerosis.

  Neuropsychology · 2025-09-24

  articleOpen accessSenior author

  OBJECTIVE: Multiple sclerosis (MS) is a neurological condition characterized by white and gray matter decline that leads to slower motor function and cognitive impairment. Although language remains relatively intact, individuals with MS often have word retrieval difficulties. Previous research suggests that these difficulties may be related to vocabulary, the number of words an individual knows, and other semantic aspects of language. However, few studies have examined phonological aspects of speech. METHOD: We examined speech in 89 individuals with MS and 88 age-matched neurotypical adults using a phonemic verbal fluency task. We took a network science approach, building a phonological network from participants' responses and their close phonological neighbors. We then examined the local network characteristics (degree, clustering coefficient) of participants' responses to assess whether responses differed between the groups. RESULTS: ² values < 1%). Finally, a forward flow analysis, which quantifies the phonological similarity between adjacent responses and provides a metric of how people search phonemic space, did not differ between groups. CONCLUSIONS: Overall, these results suggest that phonological aspects of speech remain stable in individuals with MS. Word retrieval difficulties in MS may arise from neurological changes in semantic processes, in combination with other cognitive abilities such as speed of processing and executive function, which are common in MS. (PsycInfo Database Record (c) 2026 APA, all rights reserved).

  PublisherDOI

• Neural Signatures of Word Learning: How Individual Differences Shape ERPs and Oscillations in The Early Stages of Learning a New Language

  2025-06-11

  preprintOpen accessSenior author

  A critical component of the language learning process is language control i.e., the management of lexical competition and interference from the existing language. However, how these mechanisms are engaged in early-stage learning remains unclear, particularly regarding individual differences in executive function––more specifically inhibitory control (IC), working memory (WM)––and prior bilingual experience. This study employed a pre/post short-term longitudinal design, where participants completed 10 days of Dutch language learning. Using Event-Related Potentials (ERPs) and Time-Frequency Representations (TFRs), we examined neurophysiological signatures of novel word learning and the role of IC, WM, and bilingual experience. ERP results revealed N400 reductions at post-test, marking successful lexical integration. Greater Bilingual experience predicted greater N400 reductions for noncognates, suggesting more efficient integration. In contrast, stronger IC was linked to smaller N400 reductions for noncognates, indicating greater cognitive effort in managing lexical competition. TFR analyses showed increased theta power for cognates, suggesting enhanced memory encoding, while noncognates elicited greater alpha suppression, suggesting heightened inhibitory control demands. However, individual differences did not significantly modulate these effects, as neither bilingual experience nor IC predicted alpha or theta power at post-test, suggesting that the oscillatory dynamics supporting lexical learning were driven by task demands rather than individual variability. Together, these findings indicate that bilingual experience may facilitate lexical integration, whereas IC may play a critical role in managing interference during word retrieval. The results support models of adaptive language control and highlight the dynamic interplay between linguistic experience, executive function, and lexical competition in word learning.

  PublisherOA PDFDOI

• Canvassing the whole neighborhood: A large-scale view of neighbor network structure, and how it relates to lexical processing

  Glossa Psycholinguistics · 2025-06-23

  articleOpen access

  Lexical processing reflects patterns of phonological and/or orthographic similarity among words. One approach to explaining this is to conceive of the mental lexicon as being structured according to these similarity patterns, and to model that structure as a network, most commonly by connecting each word to its immediate neighbors. Evidence that lexical processing is related to structure beyond the size of words’ immediate neighborhoods suggests that network analyses can capture psycholinguistically relevant structural patterns in the lexicon, but it remains unclear how that structure is represented in the mind and how it relates to the mechanisms used in the most prominent theoretical approaches to explaining lexical processing. To shed light on this issue, we use a latent variable approach to identify the underlying dimensions of phonological and orthographic structure in the lexicon by modeling multiple network-derived properties and testing those dimensions against word recognition data from two mega-studies. Our results confirm the importance of network measures and show that their effects on behavior are captured by three latent constructs: how densely words are packed in the region surrounding a target word (not just immediate neighbors), the interconnectedness of words residing near a target, and target words’ connectedness to multiple subregions of the network (cf. community structure). We propose that these latent constructs offer crucial guidance for interpreting the theoretical idea of structure in the mental lexicon, inviting new explanations for why words are distributed in this way, and for how structure relates to theoretical accounts of lexical processing.

  PublisherDOI

• Associative Thinking and Creative Ability in Older Adulthood

  Creativity Research Journal · 2025-01-02 · 3 citations

  articleOpen access

  Successful problem-solving and enhanced creative ability may improve physical health, cognitive well-being, and overall independence of older adults. In general, older adults who are more creative, may be better able to cope with cognitive decline and navigate everyday tasks. While previous research on creative performance in older adulthood showed age-related stability, open questions remain regarding the specific underlying cognitive basis for this invariability across the lifespan. Mediation analyses showed that intelligence measures served as underlying cognitive mechanisms for the stability of creative thinking in older age. The broader implications of these findings provide insight into the complex relationships supporting age-related preservation in creativity.

  PublisherOA PDFDOI

• The Effect of Aging on Question-Asking, Divergent Thinking, and Problem-Solving Abilities

  Creativity Research Journal · 2025-05-04 · 7 citations

  article
  PublisherDOI

• Semantic memory network resilience in aging: The role of abstract and semantically diverse words

  Cognition · 2025-10-13 · 2 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• What we mean when we say semantic: Toward a multidisciplinary semantic glossary

  Psychonomic Bulletin & Review · 2024 · 61 citations

  • Computer Science
  • Natural Language Processing
  • Psychology

  Tulving characterized semantic memory as a vast repository of meaning that underlies language and many other cognitive processes. This perspective on lexical and conceptual knowledge galvanized a new era of research undertaken by numerous fields, each with their own idiosyncratic methods and terminology. For example, "concept" has different meanings in philosophy, linguistics, and psychology. As such, many fundamental constructs used to delineate semantic theories remain underspecified and/or opaque. Weak construct specificity is among the leading causes of the replication crisis now facing psychology and related fields. Term ambiguity hinders cross-disciplinary communication, falsifiability, and incremental theory-building. Numerous cognitive subdisciplines (e.g., vision, affective neuroscience) have recently addressed these limitations via the development of consensus-based guidelines and definitions. The project to follow represents our effort to produce a multidisciplinary semantic glossary consisting of succinct definitions, background, principled dissenting views, ratings of agreement, and subjective confidence for 17 target constructs (e.g., abstractness, abstraction, concreteness, concept, embodied cognition, event semantics, lexical-semantic, modality, representation, semantic control, semantic feature, simulation, semantic distance, semantic dimension). We discuss potential benefits and pitfalls (e.g., implicit bias, prescriptiveness) of these efforts to specify a common nomenclature that other researchers might index in specifying their own theoretical perspectives (e.g., They said X, but I mean Y).

  PublisherOA PDFDOI

Recent grants

• NIH Grant R03HD059220

  NIH · $155k · 2011

• Neuroimaging of Age-Related Changes in Language

  NIH · $3.1M · 2017–2024

Frequent coauthors

• David J. Madden

  Duke Medical Center

  42 shared

• Haoyun Zhang

  Shenzhen Technology University

  36 shared

• Gregory McCarthy

  MSD (UK) Limited (United Kingdom)

  29 shared

• Ayşenil Belger

  University of North Carolina at Chapel Hill

  29 shared

• Daniel H. Mathalon

  University of California, San Francisco

  28 shared

• Micah A. Johnson

  Regeneron (United States)

  27 shared

• Jessica A. Turner

  The Ohio State University

  26 shared

• Judith M. Ford

  University of Sydney

  25 shared

Education

• MA, PhD, Psychology & Cognitive Neuroscience

  Duke University

  2005

• BA, Psychology

  Pennsylvania State University

  1999