Feeling the Strength but Not the Source: Partial Introspection in LLMs

Recent work from Anthropic claims that frontier models can sometimes detect and name injected "concepts" represented as activation directions. We test the robustness of these claims. First, we reproduce Anthropic's multi-turn "emergent introspection" result on Meta-Llama-3.1-8B-Instruct, finding that the model identifies and names the injected concept 20 percent of the time under Anthropic's original pipeline, exactly matching their reported numbers and thus showing that introspection is not exclusive to very large or capable models. Second, we systematically vary the inference prompt and find that introspection is fragile: performance collapses on closely related tasks such as multiple-choice identification of the injected concept or different prompts of binary discrimination of whether a concept was injected at all. Third, we identify a contrasting regime of partial introspection: the same model can reliably classify the strength of the coefficient of a normalized injected concept vector (as weak / moderate / strong / very strong) with up to 70 percent accuracy, far above the 25 percent chance baseline. Together, these results provide more evidence for Anthropic's claim that language models effectively compute a function of their baseline, internal representations during introspection; however, these self-reports about those representations are narrow and prompt-sensitive. Our code is available at https://github.com/elyhahami18/CS2881-Introspection.