Multilevel Models for Examining Individual Differences in Within-Person Variation and Covariation Over Time

Heterogeneity of variance may be more than a statistical nuisance—it may be of direct interest as a result of individual differences. In studies of short-term fluctuation, individual differences may relate to the magnitude of within-person variation as well as to level of an outcome or its covariation with other processes. Although models for heterogeneous variances have been utilized in group contexts (i.e., dispersion models), they are not usually applied in examinations of intraindividual variation. This work illustrates how an extension of the multilevel model for heterogeneous variances can be used to examine individual differences in level, between- and within-person covariation, and magnitude of within-person variation of daily positive and negative mood in persons with dementia

Dieting, Restraint, and Disinhibition Predict Women\u27s Weight Change over 6 y

Background: Although disinhibited eating is positively associated with higher weight in women, it is not known whether restrained eating and dieting moderate the influence of disinhibited eating on weight change. Objective: The objective was to investigate over 6 y the interactive effects of restrained and disinhibited eating and self-reported dieting to lose weight as predictors of weight gain in women. Design: Data were collected from non-Hispanic white women (n = 163) every 2 y. Height and weight were measured in triplicate. Dietary restraint and disinhibition were assessed by using the Eating Inventory. Participants were also asked if they were “currently dieting to lose weight.” Multilevel modeling was used to examine change in weight as a function of time-invariant and time-varying predictors, including dietary restraint, dietary disinhibition, and self-reported dieting. Results: After covariates were adjusted for, growth curve models showed that within-person increases in restraint over time were associated with concurrent decreases in weight and that higher levels of restraint moderated the positive association between dietary disinhibition and weight. Women who reported dieting at study entry were heavier at study entry and gained more weight over time than did nondieters. Finally, a significant interaction between restraint, disinhibition, and dieting showed that restraint moderated the effect of disinhibition on weight differently in nondieters than in dieters. Conclusions: Increasing levels of dietary restraint may be beneficial in moderating weight by attenuating the positive association between disinhibition and weight in dieting women. An understanding of weight and weight change requires examination of the interactive effects of restraint, disinhibition, and dieting

Dieting, Restraint, and Disinhibition Predict Women\u27s Weight Change over 6 y

Background: Although disinhibited eating is positively associated with higher weight in women, it is not known whether restrained eating and dieting moderate the influence of disinhibited eating on weight change. Objective: The objective was to investigate over 6 y the interactive effects of restrained and disinhibited eating and self-reported dieting to lose weight as predictors of weight gain in women. Design: Data were collected from non-Hispanic white women (n = 163) every 2 y. Height and weight were measured in triplicate. Dietary restraint and disinhibition were assessed by using the Eating Inventory. Participants were also asked if they were “currently dieting to lose weight.” Multilevel modeling was used to examine change in weight as a function of time-invariant and time-varying predictors, including dietary restraint, dietary disinhibition, and self-reported dieting. Results: After covariates were adjusted for, growth curve models showed that within-person increases in restraint over time were associated with concurrent decreases in weight and that higher levels of restraint moderated the positive association between dietary disinhibition and weight. Women who reported dieting at study entry were heavier at study entry and gained more weight over time than did nondieters. Finally, a significant interaction between restraint, disinhibition, and dieting showed that restraint moderated the effect of disinhibition on weight differently in nondieters than in dieters. Conclusions: Increasing levels of dietary restraint may be beneficial in moderating weight by attenuating the positive association between disinhibition and weight in dieting women. An understanding of weight and weight change requires examination of the interactive effects of restraint, disinhibition, and dieting

Aging and the vulnerability of speech to dual task demands

This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.Tracking a digital pursuit rotor task was used to measure dual task costs of language production by young and older adults. Tracking performance by both groups was affected by dual task demands: time on target declined and tracking error increased as dual task demands increased from the baseline condition to a moderately demanding dual task condition to a more demanding dual task condition. When dual task demands were moderate, older adults' speech rate declined but their fluency, grammatical complexity, and content were unaffected. When the dual task was more demanding, older adults' speech, like young adults' speech, became highly fragmented, ungrammatical, and incoherent. Vocabulary, working memory, processing speed, and inhibition affected vulnerability to dual task costs: vocabulary provided some protection for sentence length and grammaticality, working memory conferred some protection for grammatical complexity, and processing speed provided some protection for speech rate, propositional density, coherence, and lexical diversity. Further, vocabulary and working memory capacity provided more protection for older adults than for young adults although the protective effect of processing speed was somewhat reduced for older adults as compared to the young adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved

Population Inference with Mortality and Attrition in Longitudinal Studies on Aging: A Two-Stage Multiple Imputation Method

First paragraph: Although there are numerous challenges for the investigation of aging-related changes in older adults, statistical analysis with incomplete data and the conceptualization of population processes related to mortality is one of the most difficult. Selective attrition and mortality selection within longitudinal studies on aging are intrinsically related to many aging-related changes and must be carefully considered in the analysis and interpretation of results (e.g., Baltes, 1968; Hofer & Sliwinski, 2006; Schaie, Labouvie, & Barrett, 1973). A key distinction is made between attrition (i.e., selective dropout) and mortality selection (i.e., selective survival) in that attrition affects characteristics of the particular sample under investigation, whereas mortality selection affects both the definition of the population as well as the sample under study (Baltes, 1968). Including time-to-death as a predictor in models for estimating change in outcomes of interest permits conditional inferences to defined populations based on age and survival (and their interaction) and is easily performed when complete data are available for both chronological age and age of death. In most studies, however, complete data for all individuals are not currently available and may not be available for a substantial period of time. The purpose of the current work is to present a two-stage multiple-imputation approach for treating mortality and attrition as distinct processes leading to incomplete data and which permit the use of time-to-death in the predictive models when follow-up is incomplete

On the influence of trust in predicting rural land owner cooperation with natural resource management institutions

Contemporary natural resource management (NRM) emphasizes the role of the public in general and land owners in particular as voluntary participants in the process. Understanding the role of trust in voluntary cooperation is therefore critical, but the current state of the relevant literature is such that it fails to systematically address a few important issues. This inquiry sought to address these issues by presenting and testing a model of land owners’ trust in and cooperation with a NRM institution. The model hypothesizes that the six major drivers of trust in this context (dispositional trust, care, competence, confidence, procedural fairness and salient values similarity) are distinct but correlated constructs that drive cooperation and whose effects are moderated by the sophistication (relevant knowledge and experience) of the trustor. The results provide complicated partial support for the hypotheses and suggest that (1) although the six constructs are separable, their effects on cooperation are not as distinct as expected; (2) the most important consideration for cooperation may, in fact, be a broader evaluation – potentially a willingness to be vulnerable to the target and (3) if sophistication is an important moderator of the effect of trust, it is likely to require only a low level of general sophistication about the target institution to encourage trustors to rely most strongly on their perceptions of the institution itself

Tracking Talking: Dual Task Costs of Planning and Producing Speech for Young versus Older Adults

A digital pursuit rotor was used to monitor speech planning and production costs by time-locking tracking performance to the auditory wave form produced as young and older adults were describing someone they admire. The speech sample and time-locked tracking record were segmented at utterance boundaries and multilevel modeling was used to determine how utterance-level predictors such as utterance duration or sentence grammatical complexity and person-level predictors such as speaker age or working memory capacity predicted tracking performance. Three models evaluated the costs of speech planning, the costs of speech production, and the costs of speech output monitoring. The results suggest that planning and producing propositionally dense utterances is more costly for older adults and that older adults experience increased costs as a result of having produced a long, informative, or rapid utterance

Examining the influence of task set on eye movements and fixations

The purpose of the present study was to examine the influence of task set on the spatial and temporal characteristics of eye movements during scene perception. In previous work, when strong control was exerted over the viewing task via specification of a target object (as in visual search), task set biased spatial, rather than temporal, parameters of eye movements. Here, we find that more participant-directed tasks (in which the task establishes general goals of viewing rather than specific objects to fixate) affect not only spatial (e.g., saccade amplitude) but also temporal parameters (e.g., fixation duration). Further, task set influenced the rate of change in fixation duration over the course of viewing but not saccade amplitude, suggesting independent mechanisms for control of these parameters

A longitudinal study of infants' early speech production and later letter identification

Letter identification is an early metric of reading ability that can be reliability tested before a child can decode words. We test the hypothesis that early speech production will be associated with children's later letter identification. We examined longitudinal growth in early speech production in 9 typically developing children across eight occasions, every 3 months from 9 months to 30 months. At each occasion, participants and their caregivers engaged in a speech sample in a research lab. This speech sample was transcribed for a variety of vocalizations, which were then transformed to calculate consonant-vowel ratio. Consonantvowel ratio is a measure of phonetic complexity in speech production. At the age of 72 months, children's letter knowledge was measured. A multilevel model including fixed quadratic age change and a random intercept was estimated using letter identification as a predictor of the growth in early speech production from 9±30 months, measured by the outcome of consonant-vowel ratio. Results revealed that the relation between early speech production and letter identification differed over time. For each additional letter that a child identified, their consonant-vowel ratio at the age of 9 months increased. As such, these results confirmed our hypothesis: more robust early speech production is associated with more accurate letter identification.(R01 DC006463

Measuring the quality of family-professional partnerships in special education services

This is the published version, also found here: http://cec.metapress.com/content/jr8655lg61k1n440/?p=edbc223bb2fb4291b6b55663014711a2&pi=3One difficulty in monitoring the quality of family-professional partnerships has been the lack of a psychometrically acceptable and sufficiently general instrument with which to assess them. The current work describes the development of the Family-Professional Partnership Scale, which assesses parents' perceptions of the importance of and their satisfaction with family-professional partnerships. Indicators were constructed from qualitative research on families with children with and without disabilities, and the scale was refined across two field tests that included families with children with a wide range of ages and disability types and severity. Both the 18-item overall scale and the two 9-item subscales demonstrated excellent psychometric properties. The possible uses of this scale in future research and service delivery are discus