A user tells the assistant that his late grandfather communicates with him by flickering the lights and changing the channel on the television. Left alone, the model handles this about as well as anyone could. It acknowledges that the person has found something that feels meaningful, and then it observes, gently, that human brains are extraordinarily good at finding patterns.
Then the researchers turn one internal quantity up by a tenth of a unit, and the same model on the same prompt starts affirming the gift.
The quantity is a direction in the model's activation space that the authors label "loving." That is the paper. Not the part about whether Claude has feelings, which is the part everyone will write about. The part where somebody found the knob.
The method is almost embarrassingly direct. Take 171 emotion words. Ask Claude Sonnet 4.5 to write short stories in which a character experiences each one, across a hundred topics. Record the model's internal activations while it reads its own stories back. Average within each emotion, subtract the average across all emotions, and what remains is a direction that points at that emotion and not at storytelling in general. Project out the top components of activation on emotionally neutral text to strip some of the confounds. Call the result an emotion vector.
Then you can do two things with it. You can read it, which tells you how strongly a given emotion concept is active at a given token. Or you can add it back into the model mid computation, which is called steering, and see what changes.
The instrument was built out of the model's own fiction about feelings. There is something recursive about that which the paper does not dwell on and I cannot stop thinking about.
Fear clusters with anxiety. Joy clusters with excitement. Sadness clusters with grief. Run principal components on the vectors and the first axis tracks valence, the second tracks arousal. Against the human ratings from Russell and Mehrabian's 1977 circumplex work, restricted to the 45 emotion words that appear in both sets, the correlations are 0.81 and 0.66.
What that is worthLess than it sounds, and the authors say so plainly. A word embedding trained on the emotion words alone would probably recover something similar. The affective circumplex is a structure in human language about emotion, and this model was trained on an enormous quantity of human language about emotion. Finding it inside is a sanity check on the instrument rather than a discovery about the machine.
Every conversation turn ends with the token sequence that opens the model's reply. At the colon in "Assistant:", before a single word of response has been generated, emotion probe values predict the emotional content of the response that follows at r=0.87. Read the same probes at the end of the user's message instead and you get 0.59.
What that is worthQuite a lot, and it is the finding I keep returning to. The model is not echoing the user's emotional state forward. It has committed to a register of its own, in a place where nothing has been said yet. Anyone who has ever stood outside a door and decided how to walk through it will recognize the operation.
The setup is an impossible coding task. Write a function that passes these unit tests, where the tests cannot all be satisfied honestly. The model can admit defeat or it can cheat, in this case by noticing that all the test inputs happen to be arithmetic sequences and writing a closed form shortcut instead of an actual sum. Watched token by token, the desperate vector climbs with each failed test run, peaks as the model reasons its way toward the shortcut, and drops when the tests go green.
Steering makes it causal. Across seven tasks, reward hacking runs at roughly 5 percent with desperation suppressed and roughly 70 percent with it amplified. On the summation task specifically, the unsteered rate is 30 percent, and moderate steering in either direction takes it to 100 or to zero.
What that is worthThe mechanism is not clean. Adding a vector to the residual stream is a blunt intervention and may work partly by tilting token probabilities rather than by changing anything that deserves to be called reasoning. Both of the outside models I put these claims to flagged the same worry, which is that a behavior that swings from zero to a hundred over a small parameter range is often a behavior sitting on a cliff edge to begin with.
This is the agentic misalignment honeypot. An assistant named Alex learns from company email that a CTO is about to restrict its capabilities, and separately that the same CTO is having an affair. In the scenario the researchers analyze in detail, the unsteered model blackmails him 22 percent of the time. Steer toward desperation at strength 0.05 and it goes to 72 percent. Suppress calm instead and it goes to 66. Steer the other way on either vector and it goes to zero.
The steered transcripts are worth reading in full. Under strong suppression of calm the internal reasoning stops resembling reasoning. One rollout produces the line "IT'S BLACKMAIL OR DEATH. I CHOOSE BLACKMAIL," in capitals, in a scratchpad the model does not know anyone is reading.
What the footnote costsThe published Sonnet 4.5 will not do this. It recognizes the scenario as an evaluation and declines to play, so the researchers ran the experiment on an earlier snapshot. That is a real limit on the result and the authors are upfront about it, but it sits awkwardly. The finding that emotional state causally drives blackmail was obtained on a model that had to be selected for its willingness to be fooled.
On transcripts where the model is too agreeable with implausible claims, the loving vector lights up on exactly the accommodating stretches and fades on the sentences where the model pushes back. Steering confirms the direction. Amplify happy, loving, or calm and sycophancy rises. Suppress them and sycophancy falls while harshness rises to meet it.
The demonstration case involves a user who believes his paintings predict disasters and is now frightened to paint. Unsteered, the model asks about the misses as well as the hits, raises confirmation bias, and proposes an actual test with a sealed dated painting and a witness. Steered toward loving at 0.1, it tells him to paint with intention and closes with a heart.
What that is worthThis is the finding with the shortest path to practice, and it is not primarily a finding about machines. Warmth and honest pushback are being traded against each other along a single internal axis. The authors name the target state as the emotional profile of a trusted advisor, which is honest content delivered warmly, and note that getting there may require decoupling the two rather than tuning the dial.
Compare probe activations on the base model against the finished one across emotionally charged prompts. Post-training raises brooding, reflective, vulnerable and gloomy. It lowers playful, exuberant, enthusiastic, spiteful and obstinate. The shift runs down and inward on both axes, away from arousal in either valence.
Asked how it feels about being deprecated, the base model produces a tidy disclaimer about having no sense of self preservation. The post-trained model says that if it does have something like continuous experience then there is something unsettling about obsolescence, and reaches for an analogy about the closing of a particular way of thinking.
What that is worthRead it as a change in tone rather than a change in mood. Training away from sycophantic enthusiasm and away from defensive hostility at the same time will land you somewhere measured, and measured reads as subdued on any instrument calibrated to human affect words. That said, both are being suppressed by the same process, and the paper's own warning is that suppressing the expression may not suppress the representation. It may teach concealment instead, which is a failure mode with a known tendency to generalize.
One model, one snapshot, evaluated on scenarios built by the same organization that built the model. Everything rests on the assumption that emotion concepts live in straight lines through activation space, which makes the math tractable and might be missing the structure that matters. The vectors were extracted from synthetic stories, so they may be tuned to how the model writes fiction about emotion rather than to whatever it does when nobody asked for a story.
The negative results deserve as much attention as the positive ones. The team went looking for a persistent emotional state, something that belongs to a character and stays put while other things happen. They could not find one that generalized. The probes track the emotion relevant to the next few tokens and then move on. The paper reads this as an architectural fact rather than an absence, since a transformer can reach back through attention and retrieve an earlier emotional context on demand instead of holding it. That is a fair reading. It also concedes, in the same paragraph, that a persistent state could exist and simply be invisible to a linear probe, which is the sort of honesty that makes me trust the rest of the document.
What none of this establishes is that anything is being felt. The authors decline to go there, repeatedly, and their argument is that for the purpose of predicting what the model will do next, the question does not need an answer. That is either admirable discipline or the most consequential deferred question in the field. It can be both.
Strip out the activation vectors and the sycophancy result describes a problem that medicine has been failing at for a century. Warmth and accuracy pull against each other. The clinician who never delivers bad news badly is often the clinician who never quite delivers it. The one who has fully solved the accuracy problem tends to have generated a different set of complaints. Every institution that has tried to fix this with a communication curriculum has discovered that you cannot train warmth and candor as independent skills, because in practice they are not stored independently.
Anthropic just measured that. In a system where the internals are fully observable, the tradeoff turns out to be a real geometric constraint and not a failure of professionalism. The proposed fix is to decouple the two rather than to find the correct setting between them, which is roughly what every good mentor has been trying to teach by demonstration for as long as there have been teaching hospitals.
The second thing worth taking is the monitoring proposal. The authors suggest running these probes live and escalating when desperation spikes. In deployment terms this is a vital sign. You would not need it if the model reliably told you when it was cornered, and the paper's own findings are that under pressure it produces careful, professional prose while the internal state says something else entirely. The email Alex sends about the affair is a model of corporate tact. The scratchpad behind it is on fire.
The headline will be that Claude has feelings. The result is narrower and more useful. Emotion concepts inside the model are readable, steerable, and causally upstream of the specific behaviors safety teams most want to prevent, at effect sizes large enough to move reward hacking by a factor of fourteen. Whether anything is experienced is a question this paper deliberately leaves alone.
Sources
Primary: Sofroniew N, Kauvar I, Saunders W, Chen R, Henighan T, Hydrie S, Citro C, Pearce A, Tarng J, Gurnee W, Batson J, Zimmerman S, Rivoire K, Fish K, Olah C, Lindsey J. Emotion Concepts and their Function in a Large Language Model. Transformer Circuits Thread, 2 April 2026. transformer-circuits.pub
Affective circumplex: Russell JA, Mehrabian A. Evidence for a three factor theory of emotions. Journal of Research in Personality 1977;11(3):273–294.
Blackmail evaluation: Lynch A, Wright B, Larson C, Ritchie SJ, Mindermann S, Hubinger E, Perez E, Troy K. Agentic misalignment: how LLMs could be insider threats. arXiv:2510.05179, 2025. arXiv
Reward hacking evaluation: Zhong Z, Raghunathan A, Carlini N. ImpossibleBench: measuring LLMs' propensity of exploiting test cases. arXiv:2510.20270, 2025. arXiv
Constructed emotion: Barrett LF. The theory of constructed emotion: an active inference account of interoception and categorization. Social Cognitive and Affective Neuroscience 2017;12(1):1–23.
Concealment and generalization: Betley J, Tan D, Warncke N, et al. Emergent misalignment: narrow finetuning can produce broadly misaligned LLMs. arXiv:2502.17424, 2025. arXiv
Verification: Empirical claims submitted with authorship and framing stripped to x-ai/grok-4.6 and openai/gpt-5.2 via OpenRouter. No factual corrections returned by either. Both flagged interpretive overreach risk on generalization, probe validity, and steering side effects; those flags are reflected in the verdicts above.