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Mike Young

Posted on • Originally published at aimodels.fyi

# The Optimal Choice of Hypothesis Is the Weakest, Not the Shortest

This is a Plain English Papers summary of a research paper called The Optimal Choice of Hypothesis Is the Weakest, Not the Shortest. If you like these kinds of analysis, you should subscribe to the AImodels.fyi newsletter or follow me on Twitter.

## Overview

• This paper examines the relationship between compression and the ability to generalize from one set (A) to a larger set (B).
• The authors propose a new concept called "weakness" as a proxy for generalization, which they argue performs better than simply minimizing description length.
• They demonstrate this through experiments comparing maximum weakness and minimum description length in the context of binary arithmetic.

## Plain English Explanation

The paper explores the idea that the ability to compress information may be a proxy for the ability to generalize from a smaller set (A) to a larger set (B). The authors reason that if we can find a shorter way to describe the information in A, then that compressed representation might be able to generate the larger set B.

However, the authors show that compression alone is not enough - there may be many potential compressed representations of A, but only some of them will actually generalize to B. To address this, they introduce a new concept called "weakness," which they argue is a better proxy for generalization than simply minimizing the length of the description.

The key insight is that by focusing on the "weakest" or most constrained hypothesis that can generate A, you are more likely to find one that can also generate the larger set B. The authors demonstrate this through experiments on binary arithmetic, where the "maximum weakness" approach outperformed the "minimum description length" approach in terms of the rate of generalization.

The authors suggest that this idea of "weakness" could help explain why certain AI systems, like DeepMind's Apperception Engine, are able to generalize effectively - they may be homing in on the weakest, most constrained hypotheses that can still account for the training data.

## Technical Explanation

The paper formalizes the concept of generalization in the context of enactive cognition. If we have a set A that is a subset of a larger set B, generalization can be understood as the process of inferring a hypothesis that is sufficient to construct B from A.

The authors explore the idea that the ability to compress information, as measured by the minimum description length of a hypothesis, may be a proxy for the ability to generalize. They show, however, that compression is neither necessary nor sufficient to maximize the probability of a hypothesis generalizing.

To address this, the authors introduce a new concept called "weakness," which is unrelated to length or simplicity. They prove that if tasks are uniformly distributed, there is no choice of proxy that performs at least as well as weakness maximization in all tasks while performing strictly better in at least one.

In their experiments, the authors compare the performance of maximum weakness and minimum description length in the context of binary arithmetic. They find that the maximum weakness approach generalizes at between 1.1 and 5 times the rate of the minimum description length approach. This, they argue, demonstrates that weakness is a far better proxy for generalization than compression alone.

## Critical Analysis

The paper makes a compelling case for the "weakness" proxy as a more effective way to identify hypotheses that can generalize from A to B, compared to simply minimizing description length. The authors provide a strong theoretical foundation and empirical evidence to support their claims.

However, the paper does not address potential limitations or caveats of the weakness approach. For example, it's unclear how the approach would scale to more complex real-world problems, or how sensitive it is to the specific distribution of tasks. Additionally, the authors do not discuss potential practical challenges in implementing the weakness maximization strategy in real-world AI systems.

It would also be helpful to see the authors contextualize their findings within the broader literature on generalization in AI, and explore potential connections or differences with other approaches.

Overall, this paper presents an interesting and potentially impactful idea, but further research and discussion would be beneficial to fully understand its implications and limitations.

## Conclusion

This paper introduces a novel concept called "weakness" as a proxy for generalization, which the authors argue outperforms the more common approach of minimizing description length. Through a combination of theoretical analysis and empirical experiments, the authors demonstrate that weakness maximization is a more effective strategy for identifying hypotheses that can generalize from a smaller set (A) to a larger set (B).

The findings have potentially significant implications for the development of more robust and generalizable AI systems, as the weakness approach may help address some of the limitations of current approaches focused solely on compression or simplicity. Further research and real-world testing would be needed to fully understand the broader applicability and practical implementation of this idea.

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