Time poses several challenges to longitudinal perspectives, an example of this would be when it comes to ensure measurement invariance of constructs or to assess people evaluations of past events. This symposium brings together researchers from the Swiss National Center of Competence in Research LIVES and those interested in longitudinal perspectives to explore these challenges and discuss the opportunities they also entail.

First, introducing the issue of measurement invariance, Brodbeck and colleagues examine standardized inventories of marital satisfaction and psychopathological symptoms. In two 2-waves studies on married individuals and on patients before and after psychotherapy, respectively, this team presents the evolution of these constructs over time. Sarrasin then showcases the invariance of a 5-item self-esteem scale with multigroup confirmatory factor analyses in the tumultuous context of late adolescence and young adulthood. Her results highlight that changes in self-esteem of this vulnerable population are mainly related to changes in their satisfaction with their body image. Finally, Morselli and colleagues present life-history calendars as a means to approach past events. Their work compares respondents’ subjective evaluations of their personal trajectory obtained with graphical representations or a differential scale and pinpoints advantages of life-history calendars.

When questionnaires are administered repeatedly over time, measurement invariance needs to be established in order to determine whether the same construct is measured with similar precision. After a short introduction to cross-sectional and longitudinal measurement invariance, these concepts are illustrated by two examples employing a confirmatory factor analysis framework for categorical data. The first example is a 10-item version of the Marital Satisfaction Inventory (Whisman, Snyder, & Beach, 2009) administered at baseline and two years later to a population sample of 1275 married individuals aged 40+ (NCCR LIVES, IP-12). Measurement invariance held only for a modified one-factor model but not the three factor model which fitted the data best at baseline. The second example is the latent structure of psychopathology assessed with the Brief Symptom Inventory (Franke, 2000) before and after psychotherapy in 526 patients. Configural factorial invariance was not confirmed and the latent structure of psychopathology was simpler after psychotherapy. Implications of these measurement invariance issues for theory, statistical analyses, and adaptation of the measures will be discussed.

Self-esteem is subject to strong variations during late adolescence and young adulthood: Not only does it drop and then rise again gradually, but also marked differences across educational groups are often found. To ensure that such within- and between-individuals comparisons are unbiased, it is necessary to verify in preliminary analyses that measurement of self-esteem is invariant. To illustrate this, data of young adults (M = 18.7, SD = 2.61) in academic (N(2013) = 147; N2014 = 115) and vocational (N(2013) = 160; N(2014) = 65) tracks from the two last waves of the Longitudinal Lausanne Youth Study (NCCR LIVES) were selected. Cross-sectional multigroup confirmatory factor analyses (MGCFA) showed no difference in the measurement of the five-item self-esteem scale across the two groups, indicating that in both years unbiased mean comparisons can be conducted. Contrary to previous research, participants in academic and vocational tracks did not differ significantly in their self-esteem. In contrast, longitudinal MGCFAs revealed one within-individuals difference: While all other items remain stable, participants reported being less satisfied with their body image as they grew older. The inclusion of this item in a composite score can lead to the erroneous conclusion that young adults’ general self-esteem decreases over time. 

Life-history calendar (LHC) methods have been increasingly used life-course research as well as other domains that are interested in the timing of events and trajectories. There is indeed a consensus on the fact that the highly structured but flexible approach of the LHC facilitates the memory of past events. Respondent's experience provide a context for retrieval of autobiographical memories and they are used as anchoring points and time landmarks for recollecting events.  The literature has shown that this method provides more reliable answers that conventional question lists on biographical retrospective data.
If the LHC method has been mainly used to collect data on factual (i.e., objective) events, a few experiences have adapted it for tapping subjective dimensions and assessing the psychological impact of events. In this study we investigate whether the LHC method can be used to asses respondents' evaluation of their own personal trajectory, by comparing two different methods. The first one relies on the use of a differential scale on which respondents indicate their evaluation. The second one maximizes the visual potential of the LHC and respondents are asked to graphically express their evaluation.