Recent work by Anthropic showed that Claude models, primarily Opus 4 and Opus 4.1, are able to introspect--detecting when external concepts have been injected into their activations. But not all of us have Opus at home! By looking at the logits, we show that a 32B open-source model that at first appears unable to introspect actually is subtly introspecting. We then show that better prompting can significantly improve introspection performance, and throw the logit lens and emergent misalignment into the mix, showing that the model can introspect when temporarily swapped for a finetune and that the final layers of the model seem to suppress reports of introspection.

We do seven experiments using the open-source Qwen2.5-Coder-32B model. See the linked post for more information, but a summary of each:

Experiment 1: We inject the concepts "cat" and "bread" into the first user / assistant turn, and show that, while the model initially appears to not be introspecting, there's actually a very slight logit shift towards 'yes' and away from 'no' on injection when answering "Do you detect an injected thought..." with "The answer is...":

' yes' shift' no' shiftinject 'cat'0.150% -> 0.522% (+0.372%)100% -> 99.609% (-0.391%)inject 'bread'0.150% -> 0.193% (+0.043%)100% -> [...]

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First published:
December 21st, 2025

Source:
https://www.lesswrong.com/posts/zD4McY4NwAsWkcmCH/small-models-can-introspect-too

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Narrated by TYPE III AUDIO.

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Images from the article:

Text excerpt discussing model circuits as an ecosystem sharing weights, with some promoting introspection conditionally based on steering.

Interface showing two chatbot examples with finetuning and persona injection methods.

Interface showing AI assistant repeating

Two line graphs showing probability percentages across layers for finetuned versus untuned models.

Four line graphs comparing steered and unsteered model probabilities across layers for different cat injection scenarios.

Four line graphs showing probability percentages across layers for injecting

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“Small Models Can Introspect, Too” by vgel

LessWrong (30+ Karma)