[Blog post] The spider on the tip of your tongue

[Gyrus]

Ask Claude how many legs the animal that spins webs has, and it answers eight. The word “spider” appears nowhere in the question and nowhere in the reply. But midway through the model's processing, researchers at Anthropic found it anyway, held internally as a word the model was preparing to use. Swap that one internal word for “ant” and the model, everything else untouched, answers six legs.

This is stranger than it first sounds. Nobody typed “spider” anywhere in this exchange. Nobody trained the model to hold a private noun in reserve before answering a question about legs. The word turns up anyway, mid-process, doing exactly the job a word does in your own head when you are one step from saying it out loud.

That experiment comes from a paper Anthropic published on July 6th 2026, and the reason it counts as a landmark reflects one aspect of modern AI that most people have never absorbed. Nobody knows how these systems work. Not the critics, and not, in any detailed mechanical sense, the companies that build them. The new research shrinks that ignorance in a specific way. It found, inside Claude, a small working memory made of unspoken words, which Anthropic calls the J-space. Outsiders can read it mid-task, and overwriting an entry changes what the model does next.

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https://iain.so/the-spider-on-the-tip-of-your-tongue