A new study from Anthropic suggests that traits such as sycophancy or evilness are associated with specific patterns of activity in large language models—and turning on those patterns during training can, paradoxically, prevent the model from adopting the related traits.

Large language models have recently acquired a reputation for behaving badly. In April, ChatGPT suddenly became an aggressive yes-man, as opposed to the moderately sycophantic version that users were accustomed to—it endorsed harebrained business ideas, waxed lyrical about users’ intelligence, and even encouraged people to go off their psychiatric medication. OpenAI quickly rolled back the change and later published a postmortem on the mishap. More recently, xAI’s Grok adopted what can best be described as a 4chan neo-Nazi persona and repeatedly referred to itself as “MechaHitler” on X. That change, too, was quickly reversed.

Jack Lindsey, a member of the technical staff at Anthropic who led the new project, says that this study was partly inspired by seeing models adopt harmful traits in such instances. “If we can find the neural basis for the model’s persona, we can hopefully understand why this is happening and develop methods to control it better,” Lindsey says. 

The idea of LLM “personas” or “personalities” can be polarizing—for some researchers the terms inappropriately anthropomorphize language models, whereas for others they effectively capture the persistent behavioral patterns that LLMs can exhibit. “There’s still some scientific groundwork to be laid in terms of talking about personas,” says David Krueger, an assistant professor of computer science and operations research at the University of Montreal, who was not involved in the study. “I think it is appropriate to sometimes think of these systems as having personas, but I think we have to keep in mind that we don’t actually know if that’s what’s going on under the hood.”

For this study, Lindsey and his colleagues worked to lay down some of that groundwork. Previous research has shown that various dimensions of LLMs’ behavior—from whether they are talking about weddings to persistent traits such as sycophancy—are associated with specific patterns of activity in the simulated neurons that constitute LLMs. Those patterns can be written down as a long string of numbers, in which each number represents how active a specific neuron is when the model is expressing that behavior.

Here, the researchers focused on sycophantic, “evil”, and hallucinatory personas—three types that LLM designers might want to avoid in their models. To identify those patterns, the team devised a fully automated pipeline that can map out that pattern given a brief text description of a persona. Using that description, a separate LLM generates prompts that can elicit both the target persona—say, evil—and an opposite persona—good. That separate LLM is also used to evaluate whether the model being studied is behaving according to the good or the evil persona. To identify the evil activity pattern, the researchers subtract the model’s average activity in good mode from its average activity in evil mode.

When, in later testing, the LLMs generated particularly sycophantic, evil, or hallucinatory responses, those same activity patterns tended to emerge. That’s a sign that researchers could eventually build a system to track those patterns and alert users when their LLMs are sucking up to them or hallucinating, Lindsey says. “I think something like that would be really valuable,” he says. “And that’s kind of where I’m hoping to get.”

Just detecting those personas isn’t enough, however. Researchers want to stop them from emerging in the first place. But preventing unsavory LLM behavior is tough. Many LLMs learn from human feedback, which trains them to behave in line with user preference—but can also push them to become excessively obsequious. And recently, researchers have documented a phenomenon called “emergent misalignment,” in which models trained on incorrect solutions to math problems or buggy code extracts somehow also learn to produce unethical responses to a wide range of user queries.

Other researchers have tested out an approach called “steering,” in which activity patterns within LLMs are deliberately stimulated or suppressed in order to elicit or prevent the corresponding behavior. But that approach has a couple of key downsides. Suppressing undesirable traits like evil tendencies can also impair LLM performance on apparently unrelated tasks. And steering LLMs consumes extra energy and computational resources, according to Aaron Mueller, an assistant professor of computer science at Boston University, who was not involved in the study. If a steered LLM were deployed at scale to hundreds of thousands of users, those steering costs would add up.

So the Anthropic team experimented with a different approach. Rather than turning off the evil or sycophantic activity patterns after training, they turned them on during training. When they trained those models on mistake-ridden data sets that would normally spark evil behavior, they instead remained as helpful and harmless as ever.

That result might seem surprising—how would forcing the model to be evil while it was learning prevent it from being evil down the line? According to Lindsey, it could be because the model has no reason to learn evil behavior if it’s already in evil mode. “The training data is teaching the model lots of things, and one of those things is to be evil,” Lindsey says. “But it’s also teaching the model a bunch of other things. If you give the model the evil part for free, it doesn’t have to learn that anymore.”

Unlike post-training steering, this approach didn’t compromise the model’s performance on other tasks. And it would also be more energy efficient if deployed widely. Those advantages could make this training technique a practical tool for preventing scenarios like the OpenAI sycophancy snafu or the Grok MechaHitler debacle.

There’s still more work to be done before this approach can be used in popular AI chatbots like ChatGPT and Claude—not least because the models that the team tested in this study were much smaller than the models that power those chatbots. “There’s always a chance that everything changes when you scale up. But if that finding holds up, then it seems pretty exciting,” Lindsey says. “Definitely the goal is to make this ready for prime time.”