Joris Postmus

Joris Postmus

AI Researcher & Developer

Amsterdam, Netherlands

About

I think AI is the most significant human invention of our time, and as someone in the field, I feel a real responsibility to help make sure it develops in ways that are genuinely good.

This is what originally got me into AI safety. I previously co-founded AISIG, which started as a student initiative in Groningen and later became SAIN Groningen, helping form the national AI safety organization in the Netherlands. I still serve on the advisory board in Groningen. I also do research on making language models more interpretable and steerable, including work on controlling model behavior presented at a NeurIPS workshop.

Over the years, I've noticed that the problems I care about most deeply often trace back to the same human patterns. Growing disconnection and polarization, collapsing epistemics, and an inability to coordinate even when the stakes are existential. I think a lot of this comes down to ego, self-deception, a fundamental disconnect from how our own minds actually work, and a prisoner's dilemma playing out at a global scale. I also think AI, if developed and used properly, gives us a real chance to help people grow past those patterns, epistemically, cognitively, and spiritually, at a scale that was never possible before.

Given where my skills, personal interests, and sense of purpose point right now, Waking Up is where I want to focus. I've used the app for over five years, and the practice has deeply transformed how I think, experience, and relate to myself and others. In my current R&D role, I'm bringing what I've learned across AI safety research, engineering, and product development to what I believe is the most important mission I could be contributing to right now.

Experience

AI R&D – Present

Waking Up (Contractor)

I've used Waking Up for over five years, and the practice has meaningfully changed my life, as it has for many others. In my current R&D role, I'm drawing on what I've learned across AI safety research, engineering, and product development to help extend that impact to more people. I believe this may be one of the most important things technology can help us do. The way we understand ourselves and relate to experience shapes how we live, make decisions, and treat one another, and I think it sits beneath many of the deepest problems we face.

Co-Founder & Co-Director

AISIG, now SAIN Groningen

I co-founded AISIG as a student initiative in Groningen. Over three years, we grew it into a broader AI safety organization, organizing more than 20 events, running courses for over 60 students, and supporting research that reached NeurIPS and ICLR. AISIG later became SAIN Groningen and helped form Safe AI Netherlands, the national AI safety organization. I continue to serve on the advisory board in Groningen.

Joris Postmus presenting on existential risk from AI to a packed lecture hall of over 100 students at the University of Groningen
Opening an AISIG event at the University of Groningen.
Co-Founder

MomentumAI

I co-founded MomentumAI to help European organizations adopt AI safely and effectively. During my time there, we worked on a secure platform intended to give teams a clearer way to use AI across their organization, with control over their data, choice of models, and how those models were used.

Director of Engineering

Yara AI

As the first hire, I led engineering for a personalized self-improvement platform developed with clinical experts. My work spanned full-stack development, AI safety, and product design.

Teaching Assistant & Student Mentor

University of Groningen

TA for Introduction to Artificial Intelligence and Basic Scientific Skills. Mentored ~10 students per year through individual and group sessions. Separately selected as a Study Buddy, providing one-on-one academic coaching for students with ASD or ADHD under professional supervision.

Research

Steering Large Language Models using Conceptors: Improving Addition-Based Activation Engineering

NeurIPS 2024 · Workshop on Foundation Model Interventions

Joris Postmus, Steven Abreu

Visualization of conceptor steering vs. traditional additive steering for LLMs
Conceptor steering (bottom right) represents steering targets as ellipsoids rather than single points, enabling more precise and compositional model control.

This work explores conceptors as a way to steer language model behavior. Rather than representing a target as a single point in activation space, conceptors represent patterns as ellipsoidal regions. In our experiments, this gave us more precise control across several steering tasks and allowed us to combine objectives using Boolean operations such as AND, OR, and NOT.

Joris Postmus presenting his poster on conceptor steering for LLMs at the NeurIPS 2024 conference in Vancouver
Presenting at the MINT Workshop (Foundation Model Interventions), NeurIPS 2024, Vancouver.

Education

BSc Artificial Intelligence

University of Groningen · 2020–2024

Final grade: 8.3/10 · Thesis: 9.5/10 (Conceptor steering for LLMs)

BSc Computing Science

University of Groningen · 2022–2025

High School

Malvern Collegiate Institute, Toronto · 2016–2020

Gold medal in province-wide coding contest (Skills Ontario) · Highest mark in Computer Science · Avg. 96%

Building

I started programming when I was about ten, making video games to play with friends. That turned into web development, then software tools, then AI applications. It's always been my main creative outlet. Some of those early projects are still playable at jorispos.github.io.

Screenshots of video games and software projects built by Joris Postmus since age 10

More About My Work

What is activation engineering?+

Activation engineering steers the behavior of large language models by modifying their internal activations during inference. My research explores conceptors as an alternative to traditional vector-based approaches, allowing multiple steering objectives to be combined using Boolean operations such as AND, OR, and NOT.

What is conceptor steering?+

Conceptor steering is a method Steven Abreu and I developed for controlling large language model behavior. Unlike traditional activation engineering that uses single vectors, conceptors represent steering targets as ellipsoids in high-dimensional activation space. This allows steering objectives to be combined using Boolean algebra. We presented the work at the NeurIPS 2024 Workshop on Foundation Model Interventions.

What was AISIG?+

AISIG was the AI Safety Initiative Groningen, a student-led organization I co-founded in 2022. We ran courses, workshops, events, and research projects to help people understand and work on AI risks. It later became SAIN Groningen and helped form Safe AI Netherlands, a national organization with chapters in Groningen, Amsterdam, and Utrecht. I continue to serve on the advisory board in Groningen.

Feel free to get in touch if you'd like to talk about AI, research, or something I've written.