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Risks from Learned Optimization

paper

Authors

Evan Hubinger·Chris van Merwijk·Vladimir Mikulik·Joar Skalse·Scott Garrabrant

Credibility Rating

3/5
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Good quality. Reputable source with community review or editorial standards, but less rigorous than peer-reviewed venues.

Rating inherited from publication venue: arXiv

Foundational paper introducing mesa-optimization, analyzing risks when learned models become optimizers themselves, directly addressing transparency and safety concerns in advanced ML systems.

Paper Details

Citations
0
20 influential
Year
2025
Methodology
survey

Metadata

arxiv preprintprimary source

Abstract

We analyze the type of learned optimization that occurs when a learned model (such as a neural network) is itself an optimizer - a situation we refer to as mesa-optimization, a neologism we introduce in this paper. We believe that the possibility of mesa-optimization raises two important questions for the safety and transparency of advanced machine learning systems. First, under what circumstances will learned models be optimizers, including when they should not be? Second, when a learned model is an optimizer, what will its objective be - how will it differ from the loss function it was trained under - and how can it be aligned? In this paper, we provide an in-depth analysis of these two primary questions and provide an overview of topics for future research.

Summary

This paper introduces the concept of mesa-optimization, where a learned model (such as a neural network) functions as an optimizer itself. The authors analyze two critical safety concerns: (1) identifying when and why learned models become optimizers, and (2) understanding how a mesa-optimizer's objective function may diverge from its training loss and how to ensure alignment. The paper provides a comprehensive framework for understanding these phenomena and outlines important directions for future research in AI safety and transparency.

Cited by 17 pages

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# Risks from Learned Optimization    in Advanced Machine Learning Systems

Evan Hubinger
Alphabetical order. Equal contribution.
Chris van Merwijk11footnotemark: 1 Vladimir Mikulik11footnotemark: 1 Joar Skalse11footnotemark: 1 and Scott Garrabrant
With special thanks to Paul Christiano, Eric Drexler, Rob Bensinger, Jan Leike, Rohin Shah, William Saunders, Buck Shlegeris, David Dalrymple, Abram Demski, Stuart Armstrong, Linda Linsefors, Carl Shulman, Toby Ord, Kate Woolverton, and everyone else who provided feedback on earlier versions of this paper.

(June 11, 2019)

###### Abstract

We analyze the type of learned optimization that occurs when a learned model (such as a neural network) is itself an optimizer—a situation we refer to as mesa-optimization, a neologism we introduce in this paper. We believe that the possibility of mesa-optimization raises two important questions for the safety and transparency of advanced machine learning systems. First, under what circumstances will learned models be optimizers, including when they should not be? Second, when a learned model is an optimizer, what will its objective be—how will it differ from the loss function it was trained under—and how can it be aligned? In this paper, we provide an in-depth analysis of these two primary questions and provide an overview of topics for future research.

## 1 Introduction

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We introduce the concept of mesa-optimization as well as many relevant terms and concepts related to it, such as what makes a system an optimizer, the difference between base and mesa- optimizers, and our two key problems: unintended optimization and inner alignment.

In machine learning, we do not manually program each individual parameter of our models. Instead, we specify an objective function that captures what we want the system to do and a learning algorithm to optimize the system for that objective. In this paper, we present a framework that distinguishes what a system is optimized to do (its “purpose”), from what it optimizes for (its “goal”), if it optimizes for anything at all. While all AI systems are optimized for something (have a purpose), whether they actually optimize for anything (pursue a goal) is non-trivial. We will say that a system is an optimizer if it is internally searching through a search space (consisting of possible outputs, policies, plans, strategies, or similar) looking for those elements that score high according to some objective function that is explicitly represented within the system. Learning algorithms in machine learning are optimizers because they search through a space of possible parameters—e.g. neural network weights—and improve the parameters with respect to some objective. Planning algorithms are also optimizers, since they search through possible plans, picking those that do well according to some objective.

Whether a system is an optimizer is a property of its internal structure—what algorithm it is physically implementing—and

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