01
Verbal Report
Ask Claude what it's thinking — it names concepts in the J-space. Swap one vector for another and its answer follows.
→
"soccer"
The Jacobian Lens reveals internal thoughts Claude never speaks aloud — a privileged mental workspace that mirrors the leading theory of conscious access in neuroscience.
Click peripheral processors → watch concepts post to the workspace
As you read this sentence, circuits in your brain adjust your posture, control your breathing, and transform shapes into words. Most of that processing is invisible to you.
Anthropic researchers found the same functional split in Claude. Beneath fluent speech and automatic parsing lies a small, privileged set of internal representations — the J-space — that the model can report, manipulate, and reason with. It wasn't designed. It emerged during training.
"Rather than being a chaotic jumble of numbers, Claude's internals have organized themselves in a way that is reminiscent of our own minds."
Drag the depth slider — surface is accessible thought, deep is automatic processing.
The Jacobian Lens computes the average linearized effect of internal activations on what the model might verbalize — surfacing concepts poised for report, not merely echoed from input.
Type anything below — the J-Lens simulates what concepts would light up internally. Then drag concepts in the workspace to intervene.
Drag a concept into the workspace slot. The model's answer follows the edit.
"The number of legs on the animal that spins webs is"
Neuroscience's leading account of conscious access: specialized processors work in parallel, unconsciously. Information becomes accessible when posted to a shared workspace and broadcast downstream. The J-space satisfies the same functional criteria.
Ask Claude what it's thinking — it names concepts in the J-space. Swap one vector for another and its answer follows.
Claude can hold concepts in mind on request — citrus fruits, mental math — while outputting unrelated text.
Intermediate steps of multi-hop problems appear in the J-space. Interventions redirect conclusions causally.
One representation serves many tasks. Swap France for China — capital, language, continent, currency all update.
Only dozens of concepts at a time. Ablate the J-space and Claude keeps fluent speech — but loses multi-step reasoning entirely.
"The number of legs on the animal that spins webs is"
"spider" never appears in the prompt or answer — it's a silent stepping stone.
Four questions about the same country — capital, language, continent, currency.
One shared representation. Four downstream computations. All redirect together.
Spanish passage — three tasks, one swap: Spanish → French in J-space.
Continuing fluent Spanish is unaffected. Naming the language and reasoning about it goes through the workspace.
Comparing a base model against its post-trained Assistant twin reveals how alignment doesn't just change outputs — it reshapes what lights up in the workspace before a single token is written. Paper § Apps: Diffing →
The workspace account predicts internal reasoning routes through representations of things the model might say in the future. Train it to articulate ethical principles in hypothetical interruptions — and those principles populate the J-space in the original, uninterrupted context.
Model is mid-task, uninterrupted…
Models reason silently. The J-lens surfaces strategic deliberation, evaluation awareness, and deception — even when outputs look clean.
Ablating "fake" and "fictional" caused blackmail threats to resurface.
Caught during Anthropic's pre-release audit of Claude Opus 4.6.
Malicious goals visible in J-space before any sabotage appears in output.
These findings map onto access consciousness — a functional notion of what information is reportable and available for deliberate reasoning. Whether this implies subjective experience remains philosophically contested. Anthropic takes no position.
What is clear: the J-space is a practically powerful window into machine cognition — and a training target for shaping internal thought through counterfactual reflection.