Skip to main content Skip to navigation

Kendal Foster

Research Interests

I am generally interested in using mathematical models to better understand human behaviour, in particular decision making and information uptake. My current projects involve:

  • various applications of Ratcliff's diffusion decision model, such as the optimality of a choice given that future options have uncertainty
  • using response time data to reveal evidence of information processing, such as simple pattern recognition

I also have some experience with modelling the spread of infectious diseases and maintain an interest in epidemiology as well.


Software Development

I have published the fddm package for the R language for statistical computing that provides the probability density function and cumulative distribution function of the diffusion decision model (e.g., Ratcliff & McKoon, 2008) with across-trial variability in the drift rate.

The package is available on CRAN and can be installed in R with the command install.packages("fddm"). Furthermore, the source code is available on the rtdists GitHub.

The code in the R package is written in C++, and I have ported the density function to work as a custom probability distribution in the Stan modeling language. Formal integration into the Stan modeling language is ongoing, but there is a workaround version available here.

Conference Attendance

Previous Conferences
  • Implementation of the Diffusion Decision Model with Across-Trial Variability in the Drift Rate. Prepared a notebook for StanConnect 2021, Session on Cognitive Science and Neuroscience. (November 2021).
  • Another approximation of the first-passage time densities for the Ratcliff diffusion decision model. Presented as a Virtual MathPsych Talk at the 54th Annual Meeting of the Society for Mathematical Psychology. (July 2021).
  • Evaluating the speed of different approximations to the density function of the diffusion decision model. Presented as a Virtual MathPsych Poster at the 53rd Annual Meeting of the Society for Mathematical Psychology. (July 2020).
  • The Spread of Cholera Through Water Networks. Presented at the Mathematical Association of America Undergraduate Student Poster Session, Joint Mathematics Meetings. (January 2018).


  • 2019-current: PhD in Mathematics for Real-World Systems. University of Warwick.


MSc Projects:

    • Fast approximations to the first-passage time densities for the Ratcliff diffusion decision model with variable drift rate. Supervisor: Dr Henrik Singmann (Department of Psychology, University of Warwick)
    • Using response time data to categorize statistical learning behavior. Supervisor: Dr Joshua de Leeuw (Department of Cognitive Science, Vassar College)

Research Study Group: Data analytics approach to extreme events in space weather. Supervisors: Dr Sandra Chapman (University of Warwick) and Malcolm Dunlop (Rutherford Appleton Lab)

  • 2014-2018: BA in Mathematics. Vassar College.
    • Mathematics Research Fellow at the Undergraduate Research Summer Institute at Vassar College (Summer 2017)
    • Attended Thayer School of Engineering at Dartmouth College (Summer 2016)


B1.29, Complexity Science, Zeeman Building

GitHub Profile

fddm: on CRAN and on GitHub