– Wits University
Jess Rees and Tristan Bester have been awarded the highly competitive 2025 Google PhD Fellowship.
This fellowship recognizes outstanding PhD students in Wits University’s School of Computer Science and Applied Mathematics (CSAM) whose research demonstrates the potential for ground-breaking scientific contributions and meaningful social impact, particularly in areas where advances in computing benefit communities around the world.
The Google PhD Fellowship program supports outstanding graduate students pursuing innovative research in areas related to Google, such as machine learning, artificial intelligence, and their applications. Fellows are selected through a rigorous international process and are recognized not only for academic excellence but also for the ambition of their work to address real-world challenges and shape the future of technology.
Advances in AI for Healthcare: Jess Rees
Jess Rees is supervised by Distinguished Professor Bruce Bassett at CSAM and is recognized for her research into the use of AI in healthcare, with a particular focus on improving clinical diagnosis and strengthening healthcare systems in South Africa.
Reflecting on the award, Rees said he was “excited and honored” and said the fellowship is a powerful validation of the potential impact of his research. “The potential to influence the way AI is developed for healthcare and make a significant positive contribution to South Africa’s healthcare system is a huge motivator,” she said. “Through my work, I have an even stronger desire to contribute to both this field and this country.”
Rees emphasized that the freedom this fellowship provides allows him to focus fully on his PhD research and build collaborations across CSAM, the Faculty of Health Sciences, and the Machine Intelligence and Neural Discovery (MIND) Institute.
She is also enthusiastic about the mentorship opportunities offered through Google and our global community of postdocs, adding that she is “looking forward to working diligently to develop new algorithms for clinical diagnostics.”
Previously a lead data scientist at Discovery Health, where he worked for nine years, Rees moved into a full-time PhD in computer science at Wits. Her career is rooted in natural language processing, and her recent research focuses on large-scale language models and generative AI.
In 2024 she will one of email and guardian“200 South African Youth” For contributions to technology and innovation.
Her doctoral research will focus on multi-agent AI systems for sequential clinical diagnosis, with the aim of providing practical and impactful tools for healthcare.
Strengthen your AI fundamentals: Tristan Bester
Tristan Bester was awarded a Google PhD Fellowship for his work in the fundamentals of machine learning, particularly at the intersection of reinforcement learning and symbolic AI.
“I am honored to receive the Google PhD Fellowship in Machine Learning and ML Fundamentals,” said Bester. “It’s a real honor for a prestigious institution like Google to support my research and recognize the importance of my work. This motivates me to continue pushing the boundaries of AI and machine learning.”
Bester is a PhD candidate in Computer Science at Wits, supervised by Professor Benjamin Rosman, Director of the MIND Institute, and Dr Steven James and Dr Geraud Nangue Tasse from CSAM. Notably, James was also a Google PhD Fellow in 2018, highlighting the ongoing and continuing impact of this fellowship on machine learning research in Africa.
Bester’s research focuses on the fundamental theory underlying modern AI systems, with an emphasis on understanding why algorithms work, when they fail, and how to design them more reliably.
His research aims to bridge neural and symbolic approaches to AI, integrating low-level learning and high-level reasoning. He introduced a counting reward machine. The first Turing-complete framework for state machine-based reward modelingestablishes a new theoretical foundation for optimal behavior in reinforcement learning tasks that require complex temporal reasoning.
Building on this, my doctoral research explores optimal knowledge transfer between subtasks, principled automatic reward design, and synthesis of task structures from natural language, and develops rigorous general-purpose algorithms that improve the reliability, interpretability, and scalability of reinforcement learning.
Global recognition, regional influence
Rees and Bester’s success underpins Wits University’s growing international recognition as a world-class AI and machine learning research hub. Their work exemplifies how basic theory and applied research can work together to address pressing societal challenges, from healthcare delivery to developing more robust, reliable, and intelligent systems.
As well as supporting these students individually, the Google PhD Fellowship will strengthen the wider research ecosystem at Wits and across Africa, enabling talented researchers to pursue ambitious ideas, build global collaborations and contribute knowledge with lasting impact.
