Capturing a mentalized moment: A pilot study of the psychometric properties of a novel assessment method of mentalizing in daily life

Mentalizing, the capacity to consider mental states, is a fundamental and essential capacity that is associated with mental health. Studies mostly assess mentalizing in lab, neglecting its ecological aspects and short-term fluctuations. The current study presents preliminary psychometric findings from a novel method of assessing mentalizing dynamics in daily life. We also examined how daily life mentalizing is related to features of borderline personality disorder (BPD) which is known to show mentalizing impairments. Twenty non-clinical participants were interviewed for mentalizing capacity and completed self-report measures of mentalizing and BPD features at baseline. Then, participants completed a weeklong ecological momentary assessment (EMA) including six daily surveys of self-reported mentalizing and audio-recorded descriptions of current mental states, and a continuous assessment of stress using wearable devices. Narrative materials were coded using an observer-rated measure of mentalizing. Completion rates were high (M = 94%; N _EMAs = 726). Lab and EMA-based observer-rated mentalizing were moderately correlated (r =.41). About 67% of the variability in observer-rated mentalizing was at the within-person level and inter-rater reliability was fair (0.50 – 0.57). Better momentary self-reported mentalizing predicted better momentary observer-rated mentalizing. Better momentary observer-rated mentalizing predicted greater stress levels. BPD features tended to predict larger fluctuations in momentary observer-rated mentalizing.The novel method provides an ecological way to assess momentary mentalizing with adequate convergent and predictive validity. The preliminary findings show that mentalizing is highly dynamic in daily life and suggest that these dynamics are possibly related to momentary stress and BPD features.