Robert S. Stawski

Persons as Contexts: Evaluating Between-Person and Within-Person Effects in Longitudinal Analysis

Relationships among multiple variables over time are of interest in many developmental areas and are frequently examined using time-varying predictors in multilevel models. Yet an incomplete specification of time-varying predictors will usually result in biased model effects. Specifically, the impact of constant, between-person sources of variation must be differentiated from the impact of time-specific, within-person sources of variation - that is, persons should be modeled as contexts. The current didactic article expands upon previous work to address why and how to model persons as contexts in longitudinal analysis. An electronic appendix of syntax for estimating these models is also provided.

Reported Exposure and Emotional Reactivity to Daily Stressors: The Roles of Adult-Age and Global Perceived Stress

A central goal of daily stress research is to identify resilience and vulnerability factors associated with exposure and reactivity to daily stressors. The present study examined how age differences and global perceptions of stress relate to exposure and emotional reactivity to daily stressors. Sixty-seven younger (M age = 20) and 116 older (M age = 80) adults completed a daily stress diary and measures of positive and negative affect on 6 days over a 14-day period. Participants also completed a measure of global perceived stress. Results revealed that reported exposure to daily stressors is reduced in old age but that emotional reactivity to daily stressors did not differ between younger and older adults. Global perceived stress was associated with greater reported exposure to daily stressors in older adults and greater stress-related increases in negative affect in younger adults. Furthermore, across days on which daily stressors were reported, intraindividual variability in the number and severity of stressors reported was associated with increased negative affect, but only among younger adults.

Intraindividual coupling of daily stress and cognition.

Most psychological theories predict associations among processes that transpire within individuals. However, these theories are often tested by examining relationships at the between-persons (BP) rather than the within-persons (WP) level. The authors examined the WP and BP relationships between daily stress and daily variability in cognitive performance. Daily stress and cognitive performance were assessed on 6 occasions in 108 older adults and 68 young adults. WP variability in stress predicted WP variability in response times (RTs) on a 2-back working memory task in both younger and older adults. That is, RTs were slower on high-stress days compared with low-stress days. There was evidence of an amplified WP stress effect in the older adults on a serial attention task. There was no evidence of stress effects on simple versions of these tasks that placed minimal demands on working memory. These results are consistent with theories that postulate that stress-related cognitive interference competes for attentional resources.

Interindividual Differences and Intraindividual Variability in the Cortisol Awakening Response: An Examination of Age and Gender

This article shows age and gender differences in the magnitude and day-to-day variability of the cortisol awakening response (CAR) using a national sample of 1,143 adults who completed the second wave of the National Study of Daily Experiences, a part of the Midlife Development in the United States survey. Participants between the ages of 33 and 84 years completed 8 consecutive nightly interviews and provided 4 saliva samples (upon waking, 30 min after waking, before lunch, and before bed) on 4 consecutive interview days. Results revealed substantial day-to-day variability in the CAR as well as significant AgexGender interactions, indicating that although no systematic age-related differences emerged for women, the magnitude and day-to-day variability of the CAR increased with age among men.

Intraindividual Change and Variability in Daily Stress Processes: Findings From Two Measurement-Burst Diary Studies

There is little longitudinal information on aging-related changes in emotional responses to negative events. In the present article, we examined intraindividual change and variability in the within-person coupling of daily stress and negative affect using data from 2 measurement-burst daily diary studies. Three main findings emerged. First, average reactivity to daily stress increased longitudinally, and this increase was evident across most of the adult lifespan. Second, individual differences in emotional reactivity to daily stress exhibited long-term temporal stability, but this stability was greatest in midlife and decreased in old age. Third, reactivity to daily stress varied reliably within-persons (across-time), with individuals exhibiting higher levels of reactivity during times when reporting high levels of global subject stress in the previous month. Taken together, the present results emphasize the importance of modeling dynamic psychosocial and aging processes that operate across different time scales for understanding age-related changes in daily stress processes.

What's So Special About Working Memory? An Examination of the Relationships Among Working Memory, Secondary Memory, and Fluid Intelligence

Working memory capacity (WMC) has received attention across many areas of psychology, in part because of its relationship with intelligence. The mechanism underlying the relationship is unknown, but the nature of typical WMC tasks has led to two hypothesized mechanisms: secondary-memory processes (e.g., search and retrieval) and the maintenance of information in the face of distraction. In the present study, participants (N = 383) completed a battery of cognitive tasks assessing processing speed, primary memory, working memory, secondary memory, and fluid intelligence. Secondary memory was the strongest predictor of fluid intelligence and added unique predictive value in models that accounted for working memory. In contrast, after accounting for the variance in fluid intelligence associated with the secondary-memory construct, the working memory construct did not significantly predict variability in fluid intelligence. Therefore, the secondary-memory requirements shared by many memory tasks may be responsible for the relationship between WMC and fluid intelligence, making the relationship less unique than is often supposed.

Adult age and Digit Symbol Substitution performance: A meta-analysis

This article reports the results of a meta-analysis of the effects of age, education, and estimated year of measurement on scores from the Wechsler Adult Intelligence Scale and the Wechsler Adult Intelligence Scale-Revised Digit Symbol Substitution Test. Analysis of effect sizes for age reported in 141 studies published between 1986 and 2002 indicated a mean standardized difference of -2.07. Age accounted for 86% of the variance in a regression model using age, education, and year submitted as predictors of Digit Symbol scores. There was no association between years of education or year submitted and Digit Symbol scores for younger adults or older adults.

Psychosocial and Biological Markers of Daily Lives of Midlife Parents of Children with Disabilities

Using daily telephone interviews, 82 midlife parents (mean age = 57.4) of children with disabilities (mean age = 29.9) were compared with a closely matched sample of unaffected parents (N = 82) to elucidate the daily experience of nonnormative parenting. In addition, salivary cortisol samples were obtained to examine whether parents of children with disabilities had dysregulated diurnal rhythms and the extent to which the amount of time spent with children was associated with divergent patterns of cortisol expression. We found that parents of children with disabilities had similar patterns of daily time use and similar likelihood of positive daily events as the comparison group, but they had elevated levels of stress, negative affect, and physical symptoms, all reported on a daily basis. In addition, their diurnal rhythm of cortisol expression differed significantly from the comparison group, a pattern that was strongest for parents of children with disabilities on days when they spent more time with their children.

Goal clarity and financial planning activities as determinants of retirement savings contributions.

Retirement counselors, financial service professionals, and retirement intervention specialists routinely emphasize the importance of developing clear goals for the future; however, few empirical studies have focused on the benefits of retirement goal setting. In the present study, the extent to which goal clarity and financial planning activities predict retirement savings practices was examined among 100 working adults. Path analysis techniques were used to test two competing models, both of which were designed to predict savings contributions. Findings provide support for the model in which retirement goal clarity is a significant predictor of planning practices, and planning, in turn, predicts savings tendencies. Two demographic variables—income and age—were also revealed to be important elements of the model, with income accounting for roughly half of the explained variance in savings contributions. The results of this study have implications for the development of age-based models of planning, as well as implications for retirement counselors and financial planners who advise workers on long-term saving strategies.

Associations among daily stressors and salivary cortisol: Findings from the National Study of Daily Experiences

While much research has focused on linking stressful experiences to emotional and biological reactions in laboratory settings, there is an emerging interest in extending these examinations to field studies of daily life. The current study examined day-to-day associations among naturally occurring daily stressors and salivary cortisol in a national sample of adults from the second wave of the National Study of Daily Experiences (NSDE). A sample of 1694 adults (age=57, range=33-84; 44% male) completed telephone interviews detailing their stressors and emotions on eight consecutive evenings. Participants also provided saliva samples upon waking, 30min post-waking, before lunch and before bed, on four consecutive interview days resulting in 5995 days of interview/cortisol data. Analyses revealed three main findings. First, cortisol AUC was significantly higher on stressor days compared to stressor-free days, particularly for arguments and overloads at home, suggesting that daily stressors are associated with increased cortisol output, but that not all daily stressors have such an influence. Second, individuals reporting a greater frequency of stressor days also exhibited a steeper diurnal cortisol slope. Finally, daily stressor-cortisol associations were unaltered after adjustment for daily negative affect and physical symptoms. Our discussion focuses on the influence of naturally occurring daily stressors on daily cortisol and the role of daily diary approaches for studying healthy cortisol responses to psychosocial stressors outside of traditional laboratory settings.