From AI Scaling to Mechanistic Interpretability

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Let’s dive into the fascinating world of scaling laws, mechanistic interpretability, and how they impact the development of artificial intelligence. From asking why the universe responds to throwing large amounts of computing power at vast amounts of data to discussing the emergence of specific abilities in AI models, Dario, the CEO of Anthropic AI, provides an insightful perspective on the future of AI.

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Dario Amodei (Anthropic CEO) - $10 Billion Models, OpenAI, Scaling, & AGI in 2 years

Key Takeaways

  • Scaling laws are still largely a mystery, but their impact on AI development is significant.
  • Predicting specific abilities for AI models is difficult, but improvements with scaling continue to surprise researchers.
  • Value alignment and data constraints are factors that may challenge the scaling process in the near future.

Scaling Laws and How They Work

So, you’ve been wondering about scaling laws and how they seem to magically work, right? Well, let me tell you, it’s a pretty fascinating phenomenon that even the experts are still trying to wrap their heads around.

πŸ’‘ Scaling laws are kind of like those really satisfying formulas in physics – when you add enough computing power and a huge chunk of data, somehow it just…works, and leads to intelligence.

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The wild part is that we still don’t know exactly why it works so smoothly with both parameters and data quantity. It’s literally alien technology.

Some theories pop up, like how parameters and data are like buckets of water. The size of the bucket sort of determines how much data (or water) it can hold, but why it all lines up so perfectly, we still aren’t quite sure.

Now, the hard-to-swallow truth is we can’t exactly predict when new abilities will emerge, or when certain circuits will take shape. Just like how predicting the weather on a particular day is tough, but having a rough idea of what’s happening seasonally is more doable.

Example: Say a model learns to do addition. For a long time, it might not quite nail down the correct answer, but something is definitely going on “behind the scenes.” And then suddenly – bam! – it gets it right. But the question that remains is what circuit or process kicked in to make it work?

Anthropic CEO Dario Amodei argues, there’s no satisfying explanation for why throwing big blobs of compute at a wide distribution of data suddenly makes an AI intelligent. We’re still left guessing.

However, we can observe that scaling works smoothly with parameters and the amount of data, but specific abilities are harder to predict. For instance, when does an AI model learn arithmetic or programming? Surprisingly, it can sometimes be an abrupt development.

Mechanistic Interpretability

Midjourney Prompt: a female young engineer looking at a large screen displaying a neural network and a matrix of numbers trying to figure out rules and principles scribbled on a whiteboard

Now you’re probably wondering, “What’s happening behind the scenes?” Good question! We don’t know for sure, but one approach we can try is mechanistic interpretability:

πŸ’‘ Mechanistic interpretability seeks to reverse engineer neural networks, similar to how one might reverse engineer a compiled binary computer program. In essence, neural network parameters are a binary computer program running on a neural network architecture.

Mechanistic interpretability focuses on reverse-engineering neural networks weights to figure out what algorithms they’ve learned to perform well on a task. Instead of going from binary to Python, we go from neural network weights (parameters) to the underlying knowledge (algorithms) that the training process figured out to perform well on tasks.

Taking this analogy seriously, we can explore some of the big-picture questions in mechanistic interpretability. Questions that feel speculative and slippery for reverse engineering neural networks become clear if you pose the same question for reverse engineering of regular computer programs.

And it seems like many of these answers plausibly transfer back over to the neural network case. Perhaps the most interesting observation is that this analogy seems to suggest that finding and understanding interpretable neurons isn’t just one of many interesting questions. Arguably, it’s the central task.

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Think of it like circuits snapping into place. Although evidence suggests that the probability of a model getting the correct answer increases gradually, many mysteries remain.

What is mechanistic interpretability? Neel Nanda explains.

There’s no guarantee that certain abilities, like alignment and values, will emerge with scale. A model’s job is to understand and predict the world, which is about facts, not values. There are various free variables at play that may not emerge as AI scales.

If scaling plateaus before reaching human-level intelligence, we might see one of a few reasons.

  • First, data could become limited – we run out of information to continue scaling.
  • Second, compute resources might not increase enough to maintain rapid scaling progress.
  • And fundamentally, it’s possible that we just haven’t found the right architecture yet.

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Now comes the million-dollar question: Are there abilities that won’t emerge with scale? It’s quite possible that alignment and values, for example, won’t magically arise as AI models continue to grow. The models might excel at understanding and predicting the world, but that doesn’t guarantee they’ll develop their own unique values or sense of what they should do.

Attacking the Curse of Dimensionality

πŸ‘¨β€πŸš€ The Curse of Dimensionality refers to the rapid escalation of complexity that comes with adding more dimensions to data, leading to a significant spike in the computational power needed to process or analyze it.

The curse of dimensionality is a challenge for both learning and interpretability of neural networks. The input space of neural networks is high-dimensional, making it incredibly large. Therefore, it is difficult to learn a function over such a large input space without an exponential amount of data. Similarly, it is challenging to understand a function over such a large space without an exponential amount of time.

  • One way to overcome the curse of dimensionality is to study toy neural networks with low-dimensional inputs, allowing easy full understanding by dodging the problem.
  • Another approach is to study the behavior of neural networks in a neighborhood around an individual data point of interest. This is roughly the answer of saliency maps.

However, these approaches have limitations and may not be sufficient for tasks such as vision or language.

βœ… Mechanistic interpretability is another approach to overcome the curse of dimensionality.

It is worth noting that this approach is not only applicable to neural networks but also to regular reverse engineering. Programmers reverse engineering a computer program can understand its behavior, often over an incredibly high-dimensional space of inputs, because the code gives a non-exponential description of the program’s behavior. Similarly, we can aim for the same answer in the context of artificial neural networks. Ultimately, the parameters are a finite description of a neural network. Therefore, if we can somehow understand them, we can achieve mechanistic interpretability.

However, the parameters may be very large, making it challenging to achieve mechanistic interpretability.

For instance, the largest language models have hundreds of billions of parameters. Nevertheless, binary computer programs like a compiled operating system can also be very large, and we’re often able to eventually understand them.

Midjourney prompt: “from low to high dimensionality”

It is essential to note that we should not expect mechanistic interpretability to be easy or have a cookie-cutter process that can be followed. People often want interpretability to provide simple answers or a short explanation. However, we should expect mechanistic interpretability to be at least as difficult as reverse engineering a large, complicated computer program.

In summary, mechanistic interpretability is an approach to overcome the curse of dimensionality. It is not a simple process and may require a significant amount of effort to achieve. However, it is a promising approach to understand the behavior of neural networks over a high-dimensional input space.

βœ… Related: AI Scaling Laws – A Short Primer

Variables & Activations

Variables and activations are two key concepts in understanding computer programs and reverse engineering neural networks. In computer programs, a variable represents a value that can be changed or manipulated by the program.

Understanding the meaning of a variable requires understanding how it is used by the program’s operations. Similarly, in neural networks, activations are analogous to variables or memory, and understanding their meaning requires understanding how they are used by the network’s parameters.

However, unlike in computer programs, reverse engineers of neural networks do not have the benefit of variable names. Instead, they must figure out what each activation represents and how it contributes to the overall functioning of the network. This requires decomposing activations into independently understandable pieces, similar to how computer program memory is segmented into variables.

In some cases, such as attention-only transformers, all of the network’s operations can be described in terms of its inputs and outputs, allowing us to sidestep the problem of understanding activations. However, in most cases, activations are high-dimensional vectors, making them difficult to understand. Mechanistic interpretability requires decomposing activations into simpler, more understandable pieces.

To do this, researchers have developed various techniques, including activation patching and causal scrubbing, which can help identify which activations are most important for a given output.

Additionally, embeddings can be used to map activations to a more interpretable space, such as a lower-dimensional vector space.

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Overall, understanding variables and activations is crucial for reverse engineering neural networks and gaining mechanistic interpretability. By breaking down activations into simpler, more understandable pieces, we can gain insight into how the network functions and what its parameters are doing.

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Simple Memory Layout & Neurons

Neural networks can be understood in terms of operations on a collection of independent “interpretable features”.

Just as computer programs often have memory layouts that are convenient to understand, neural networks have activation functions that often encourage features to be aligned with a neuron, rather than correspond to a random linear combination of neurons.

This is because activation functions in some sense make these directions natural and useful. We call this a privileged basis. Having features align with neurons would make neural networks much easier to reverse engineer. This ability to decompose representations into independently understandable parts seems essential for the success of mechanistic interpretability.

Unfortunately, many neurons can’t be understood this way. These polysemantic neurons seem to help represent features which are not best understood in terms of individual neurons. This is a really tricky problem for reverse engineering neural networks.

Frequently Asked Questions

Common Applications of Mechanistic Interpretability in Machine Learning

Mechanistic interpretability has several applications in machine learning. One of the most common applications is to understand how a model makes predictions. This can be useful in various fields such as healthcare, finance, and transportation. Mechanistic interpretability can also help in identifying and correcting biases in the data and the model.

Challenges in Achieving Mechanistic Interpretability

One of the biggest challenges in achieving mechanistic interpretability is the complexity of the models. As the models become more complex, it becomes difficult to understand how they make predictions. Another challenge is the lack of standardized methods for achieving mechanistic interpretability.

Differences between Mechanistic Interpretability and Other Forms of Interpretability

Mechanistic interpretability differs from other forms of interpretability such as post-hoc interpretability in that it aims to understand the internal workings of the model rather than just explaining its outputs. It also differs from explainability in that it focuses on understanding the causal relationships between the inputs and outputs of the model.

Recent Advancements in Mechanistic Interpretability Research

Recent advancements in mechanistic interpretability research include the development of new techniques such as Integrated Gradients and Layer-wise Relevance Propagation. These techniques aim to provide a better understanding of how the model makes predictions and identify the most important features in the data.

Using Mechanistic Interpretability to Improve Model Performance

Mechanistic interpretability can be used to improve model performance by identifying and correcting biases in the data and the model. It can also help in identifying areas where the model is making incorrect predictions and provide insights into how to improve the model.

Potential Ethical Implications of Using Mechanistic Interpretability in Machine Learning

There are potential ethical implications of using mechanistic interpretability in machine learning. For example, the use of mechanistic interpretability can lead to the discovery of biases in the data and the model that may have negative impacts on certain groups of people. It is important to consider these ethical implications when using mechanistic interpretability in machine learning.

Let’s end this blog post with a great talk on mechanistic interpretability for the ultra-nerds out there: πŸ‘‡

Open Problems in Mechanistic Interpretability: A Whirlwind Tour

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