About

Dr. Tomiko Yoneda (Tiko), PhD, is an Assistant Professor in the Department of Psychology at UC Davis. She is passionate about researching factors that have the potential to make a positive difference in the lives of older adults. Her work emphasizes interpersonal processes and individual differences, focusing on social connection and personality traits as key determinants of health and cognition. Dr. Yoneda examines how these psychological factors interact with physiology, and how their effects vary across individuals, couples, time, contexts, and (sub)populations. Specifically, she investigates under which circumstances, for whom, and how psychological factors and social experiences shape cognitive and physical aging trajectories, and vice versa. Dr. Yoneda is deeply committed to recognizing, acknowledging, and celebrating inclusion and belongingness. She strives to adhere to approaches that are sensitive to the unique backgrounds, lived experiences, and educational goals of all students. Outside of her research and teaching, she enjoys trail running, playing sports with her son, appreciating big trees, basking in the enormity of the ocean, and wine tasting.

Research topics

• Social psychology
• Psychology
• Medicine
• Developmental psychology
• Clinical psychology
• Internal medicine

Selected publications

• Social relationships, psychological distress, and physical health in sexual minority and heterosexual middle-aged and older adults in the Canadian Longitudinal Study on Aging

  2026-02-06

  articleOpen access

  Social connections are crucial for healthy aging, and health disparities are particularly pronounced among sexual minorities. This secondary data analysis investigates longitudinal associations between social relationships and physical health in 1,057 participants of whom 26% identified as lesbian, 50% as gay, and 24% as bisexual people (Mage = 59 years, 38% women, 62% men) and a matched heterosexual control group. Participants reported social support, social isolation, and health behaviors 3 times at 3-year intervals; a subset (n = 665) provided information on psychological distress and physiological assessments. Lesbian, gay, and bisexual adults reported lower social support, higher social isolation, higher psychological distress, and lower physical activity (only men), compared to heterosexual controls. Groups did not significantly differ in nutritional risk or allostatic load. Social vulnerabilities were most prominent among gay and bisexual men as well as bisexual women, but not lesbian women. Controlling for autoregressive effects, we found little evidence for longitudinal associations of social support or social isolation with physical health. However, we found indirect associations between lower social support and subsequent worse physical health (nutritional risk, physical activity, allostatic load) mediated by increased psychological distress (both groups). Findings underscore the need for interventions to increase social belonging, and to address the unique social and physical health challenges of aging sexual minority adults.

  PublisherDOI

• Is My Loneliness Killing Me? Effects of Loneliness and Social Isolation on Transitions Between Cognitive Status Categories and Death

  OSF Preprints (OSF Preprints) · 2026-02-24

  otherOpen access

  This is a registered report, accepted in principle, investigating the individual and adjusted effects of loneliness and social isolation on the risk of cognitive outcomes and mortality.

  Publisher

• Personality change and development in adulthood.

  American Psychological Association eBooks · 2026-01-01

  book-chapter
  PublisherDOI

• Moderating Variables, Stress-eating Behaviors, and Personality Traits

  OSF Preprints (OSF Preprints) · 2026-04-13

  otherSenior author
  Publisher

• Discrepancies in loneliness and social isolation predict cognitive impairment through chronic disease burden

  Brain Behavior & Immunity - Health · 2026-04-06

  articleOpen access

  The discrepancy between loneliness and objective social isolation (social asymmetry) has been linked to poorer cognitive aging, yet the biobehavioral pathways underlying this association remain unclear. This study tested whether chronic disease burden or allostatic load mediated associations between social asymmetry and subsequent cognitive performance. We analyzed data from 840 adults (mean age = 54 years, range = 34–81 years) from the Midlife in the United States (MIDUS) Biomarker Project using structural equation modeling to test parallel mediation through allostatic load and chronic disease burden. Social asymmetry was associated with greater chronic disease burden but showed minimal association with allostatic load. Chronic disease burden significantly mediated relationships between social asymmetry and episodic memory and executive function, whereas allostatic load did not. Conclusions : Chronic disease burden showed stronger statistical evidence as an indirect pathway linking social asymmetry to subsequent cognitive outcomes than the allostatic load composite. These findings suggest that disease prevention may be an important target for preserving cognition in socially vulnerable adults. • In a national sample of adults (MIDUS), loneliness exceeding one’s level of social contact predicted poorer memory and executive function. • Chronic morbidity, not stress physiology, mediates social vulnerability effects on cognition. • Findings underscore disease prevention and management to protect cognitive health.

  PublisherDOI

• Changes in Social Asymmetry as People Age and the Effects of Personality and Socioeconomic Status

  Innovation in Aging · 2025-12-01

  articleOpen access

  Abstract Social stress related experiences are substantial public health concerns as people age. However, prior research suggests discrepancies among different aspects of social stress such as social isolation and loneliness. Social asymmetry is a concept that captures the discordance/concordance between loneliness and social isolation levels. Social asymmetry indicates how well individuals adapt to their social environment, with individuals experiencing greater loneliness than expected given their social isolation levels considered socially vulnerable and those experiencing less loneliness than expected considered socially resilient. It remains unknown how social asymmetry changes over time as people age, and how different individual and contextual factors contribute to individual differences in the change trajectory of social asymmetry. In the current project, we used data from 9 large longitudinal studies to examine changes in social asymmetry during aging and the effects of personality traits and socioeconomic status on the levels of and changes in social asymmetry. Adopting the coordinated data analysis framework allows us to synthesize the results across samples and examine the degree to which the findings are generalizable by testing different sample-level moderators. The preliminary results suggested increases in social asymmetry in late adulthood. Higher neuroticism was found to be related to higher levels of and increases in social asymmetry (social vulnerability, whereas higher extraversion, conscientiousness, and agreeableness, as well as higher SES, were related to lower levels of and decreases in social asymmetry (social resilience). The study enhances our understanding of individual differences in the dynamics of objective and subjective social stress during aging.

  PublisherOA PDFDOI

• Better Together: Momentary Physiological Benefits of Co-Experienced Positive Emotions in Late Life

  Innovation in Aging · 2025-12-01

  articleOpen access1st authorCorresponding

  Abstract Although positive emotions tend to be experienced most frequently and intensely within social interactions, most research has focused on positive emotions at the individual level. Yet, emerging research shows that shared positive emotions predict health and longevity over and above individually experienced positive emotions. However, the extent to which relationship partners co-experience positive emotions in daily life remains poorly understood. Moreover, whether positive emotions “get under the skin,” shaping proximal biomarkers in everyday life, is unclear. Drawing on Positivity Resonance Theory, we examined the links between co-experienced positive emotions and momentary cortisol levels in 321 older couples (ages 56–89). Findings showed that both relationship partners reported higher-than-usual positive emotions during 38% of the occasions they were together. Additionally, co-experienced positive emotions were linked to lower cortisol levels at the same occasion, adjusting for individually experienced positive emotions and several additional individual-level and time-varying covariates. Findings did not differ across age, sex, or relationship satisfaction, suggesting that the physiological benefits of co-experienced positive emotions are not dependent on individual or relationship characteristics. Notably, co-experienced positive emotions were also associated with lower cortisol at the subsequent assessment (but not vice versa), indicating that the benefits of co-experienced positive emotions extend beyond the immediate moment. This study highlights the important role that shared positive emotions play in promoting physiological health in older adults, providing evidence that co-experienced emotions offer benefits beyond individual experiences.

  PublisherOA PDFDOI

• Better together: Coexperienced positive emotions and cortisol secretion in the daily lives of older couples.

  Journal of Personality and Social Psychology · 2025-10-30 · 1 citations

  articleOpen access1st authorCorresponding

  An emerging body of research suggests that shared positive emotions predict health and longevity over and above individually experienced positive emotions. However, the extent to which relationship partners coexperience positive emotions in daily life remains poorly understood. Moreover, while laboratory research shows important distal effects of shared positive emotions on health and longevity, the extent to which positive emotions may "get under the skin," shaping proximal biomarkers in everyday life, is unclear. In response, the present research harmonized data from three intensive measurement studies to investigate coexperienced positive emotions in couples' daily lives and the links with momentary cortisol secretion in 321 older adult couples aged 56-89 years. Results showed that on occasions when relationship partners were together, both partners reported positive emotions higher than their usual at approximately 38% of occasions. Adjusting for age, sex, assay version, partner's mean positive emotions, diurnal cortisol rhythm, medication, behaviors that may influence cortisol secretion, and person-mean centered positive emotions, coexperienced positive emotions were associated with lower concurrent cortisol secretion. Findings did not differ across age, sex, or relationship satisfaction. Furthermore, coexperienced positive emotions were associated with lower cortisol at the subsequent assessment but not vice versa, suggesting potentially enduring physiological impacts of coexperienced positive emotions beyond the present moment. Together, findings show that coexperienced positive emotions are associated with lower momentary cortisol secretion over and beyond individually experienced positive emotions, emphasizing the importance of fostering shared positive emotions in close relationships to promote physiological responding in older adulthood. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

  PublisherDOI

• Social asymmetry and physical health in the United States and Japan.

  Health Psychology · 2025-04-15 · 4 citations

  articleOpen access

  OBJECTIVE: Social relationships are increasingly recognized as crucial determinants of health, but cultural variations in the health implications of social disconnection remain understudied. This study examines how nationality, reflecting cultural differences in social norms, moderates the relationship between social asymmetry and physical health in Japanese and U.S. adults. We hypothesized that the association between greater social asymmetry and poorer health would be attenuated in Japan compared to the United States. METHOD: The sample comprised adults aged 23-84 years from Japan (N = 1,027) and the United States (N = 6,650) participating in the Midlife in Japan and Midlife in the United States longitudinal studies. Social asymmetry was quantified as the residual score from regressing loneliness on social isolation, with positive residuals indicating higher loneliness than expected based on isolation levels. Physical health was a latent variable indicated by chronic conditions, symptoms, activities of daily living, and physical activity. Structural equation modeling examined the moderating effect of nationality on the social asymmetry-health link. RESULTS: Across both cultural contexts, greater social asymmetry (i.e., higher loneliness than predicted by isolation) was associated with worse physical health. However, as hypothesized, this relationship was significantly weaker in Japan compared to the United States, highlighting the role of cultural context in shaping the health implications of discrepant social experiences. CONCLUSIONS: Findings contribute to understanding cultural variations in the health consequences of social disconnection and emphasize the need to consider sociocultural factors when examining social determinants of health across diverse populations. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

  PublisherDOI

• Middle Adulthood Relationships and Later Cognitive Function: An 18-Year Study of Mexican-Origin Adults

  Innovation in Aging · 2025-12-01

  articleOpen accessSenior author

  Abstract Extensive evidence shows that close relationships matter for cognitive health, serving as both risk and protective factors. However, most existing literature focuses on older White adults, relies on self-reports, and centers on spousal relationships. Less is known about whether midlife spousal and child relationship experiences affect cognitive function over time, particularly in underrepresented communities. Our study addresses these gaps by focusing on middle adulthood, a period when people balance caregiving, work, and evolving family roles. Specifically, we ask whether relationship quality with partner and child (assessed via parent and child reports) shapes initial levels and long-term change in cognitive function. Drawing on data from an 18-year longitudinal study of Mexican-origin adults (N = 1,111; Mage = 38.3 at baseline), we used latent growth curve modeling to examine several relationship factors (aggregated across Years 1-10) as predictors of level and change in cognitive function assessed at Years 12, 16, and 18. Findings showed that higher relationship stability, satisfaction, warmth, and social support were associated with higher baseline cognitive function. However, higher satisfaction, warmth, and social support were also associated with steeper cognitive declines over time. In contrast, relationship instability, hostility, and conflict were unrelated to cognition, except for relationship instability predicting faster decline. Higher parent–child conflict also predicted higher baseline cognition but steeper decline. Together, these findings emphasize complex links between relationship factors and cognitive aging, suggesting supportive relationships are protective for cognition early in middle adulthood, but may also be associated with more decline later in midlife.

  PublisherOA PDFDOI

Frequent coauthors

• Graciela Muñiz‐Terrera

  University of Edinburgh

  35 shared

• Andrea M. Piccinin

  University of Victoria

  35 shared

• Eileen K. Graham

  32 shared

• Daniel K. Mroczek

  Northwestern University

  29 shared

• Scott M. Hofer

  Oregon Health & Science University

  21 shared

• Nathan A. Lewis

  University of Victoria

  21 shared

• Avron Spiro

  VA Boston Healthcare System

  16 shared

• Jonathan Rush

  University of Victoria

  15 shared

Labs

• The Healthspan LabPI