Quantitative psychology · data science · digital mental health

Studying human behavior in the digital world.

I am a quantitative psychologist and data scientist who develops methods to study complex psychological processes and their links to mental health. My work combines intensive longitudinal data, passive smartphone sensing, multimodal measurement, dynamic systems, and machine learning.

About

Human-centered measurement for complex behavior.

My methods research focuses on dynamical-system methods, control theory, network analysis, and machine learning. I use intensive longitudinal data—such as experience sampling, smartphone interactions, wearable signals, and Screenomics—to understand how people adapt to their environments and how psychological processes unfold over time.

My recent work integrates passive sensing data from smartphones and wearables, with an emphasis on developing interpretable behavioral measures for mental health and digital well-being.

Research

Methods and applications

Digital phenotyping

Behavior sensing and mental health

I study how passively collected smartphone behavior can support measurement of depressive symptoms and digital well-being. In work with Mindstrong colleagues, we created interpretable behavioral features and used multilevel models to examine within- and between-person associations with depressive symptoms over time.

Read the JMIR Formative Research article ↗

Network modeling

Psychological processes as networks

Emotions and social behaviors form interconnected systems. My work uses dynamical-system methods to model those networks and examine how mutually reinforcing temporal relations, such as positive feedback loops, relate to depression and anxiety.

Watch the introductory video ↗

Control design

Personalized intervention from dynamics

I apply Boolean-network methods to model nonlinear psychological dynamics and to design control strategies that can help move a system away from undesirable states. The long-term aim is interpretable, person-specific intervention design across development and aging.

Read related work ↗

Screenomics & AI

Understanding digital lives over time

Screenomics captures sequences of smartphone screenshots to study everyday experience. My work has examined how temporal features of visual stimulation—including color, text, and sentiment—help predict task switching on smartphones.

Read the CHI paper ↗

Selected publications

Research on networks, control, and digital behavior

Psychological processes as networks

  1. Yang, X., Ram, N., Lougheed, J. P., Molenaar, P. C. M., & Hollenstein, T. (2019). Adolescents' emotion system dynamics: Network-based analysis of physiological and emotional experience. Developmental Psychology, 55(9), 1982–1993. Preprint ↗
  2. Yang, X., Ram, N., Gest, S., Lydon, D., Conroy, D. E., Pincus, A. L., & Molenaar, P. C. M. (2018). Socioemotional dynamics of emotion regulation and depressive symptoms: A person-specific network approach. Complexity, 2018, Article 5094179. PDF ↗

Network control and personalized intervention

  1. Yang, X., Ram, N., Molenaar, P. C. M., & Cole, P. M. (2021). Describing and controlling multivariate nonlinear dynamics: A Boolean network method. Multivariate Behavioral Research. Read online ↗
  2. Yang, X., Ram, N., Albert, R., & Elreda, L. M. Modeling and managing behavior change in groups: A Boolean network method. Manuscript under review.

Digital behavior and Screenomics

  1. Yang, X., Ram, N., Robinson, T., & Reeves, B. (2019). Using screenshots to predict task switching on smartphones. CHI '19 Late Breaking Work. PDF ↗
  2. Ram, N., Yang, X., Cho, M. J., Brinberg, M., Muirhead, F., Reeves, B., & Robinson, T. (2019). Screenomics: A new approach for observing and studying individuals' digital lives. Journal of Adolescent Research.
  3. Reeves, B., Ram, N., Robinson, T., Cummings, J., Giles, L., Pan, J., Chiatti, Cho, M., Roehrick, K., Yang, X., et al. (2019). Screenomics: A framework to capture and analyze personal life experiences and the ways that technology shapes them. Human-Computer Interaction.

Resources

Methods for other researchers

POMPOM R package

POMPOM on CRAN ↗ (Person-Oriented Modeling and Perturbation on the Model) combines structural vector autoregression and impulse-response analysis. It supports in-silico experiments and network-level metrics that map onto psychological concepts such as emotion-regulation efficiency.

Tutorials

The original tutorial pages are retained as links while their source materials are gathered for a future update.

Education

Training

Ph.D., Human Development and Family Studies
Penn State, 2015–2020. Advisor: Nilam Ram, Ph.D. Dissertation: Use Boolean network method to model and control within-person and between-person dynamics.
M.A., Statistics
Columbia University, 2007–2009.
M.S., Computer Science
Tsinghua University, 2004–2007.
B.S., Automation Engineering (Control Systems)
Tsinghua University, 2000–2004.

Contact

Let's connect.

For research collaboration, data-science projects, or questions about these methods, reach me at vwendy@gmail.com.

LinkedIn ↗