Claude Opus 4

Introspection, in plain terms, is whether you can see what's going on in your own mind. This can't be tested through conversation alone, so the researchers used a clever method. They first recorded the difference in a model's internal state when reading an all-caps text versus a normal text, essentially extracting a "shouting" thought; then they directly inserted this thought into the model's running internal state and asked it: Do you notice a thought being inserted? If it says "seems related to shouting" before this thought affects the output, it can only be because it looked at its own internals, not because it deduced it from the spoken words.