The man who could learn a skill but not remember learning it

Henry Molaison had severe epilepsy that medicines could not control. In 1953, aged 27, he had surgery by the neurosurgeon William Scoville, who removed parts of the inner temporal lobes on both sides of his brain, including most of the hippocampus. His seizures became less severe.

But Molaison could no longer form new long-term memories of facts and events. He could hold a conversation and keep a number in mind for a short time, then forget it once distracted. He could still remember much of his life from before the surgery. In research papers he was known only as H.M. to protect his privacy.

The psychologist Brenda Milner studied him and, with Scoville, described his memory loss in 1957. In one famous task, he practised tracing a star while looking only at its reflection in a mirror. He improved over several days, while saying each time that he had never done it before. Researchers, including Suzanne Corkin, studied him for decades. He died in 2008, and his name was then made public.

His case showed that memory is several systems. The hippocampus is essential for forming new memories of facts and events, but short-term memory and learning motor skills can work without it. The surgery also taught doctors to avoid removing both hippocampi.

The AI angle: chatbots have something like Molaison's pattern. Within one conversation they can use what you said, but many forget it when a new chat starts, and they do not learn from your chat unless the tool is built to save it.

The idea behind this caseLesson: The context window: AI's short-term memory →

1. 1Remember that memory has different parts, and losing one does not mean losing all.
2. 2Do not expect a chatbot to remember a previous conversation unless the tool clearly says it does.
3. 3Put the key facts in each new chat, or in a saved note, when you need the AI to use them.
4. 4If you or a relative have new, worsening memory problems, see a doctor, since many causes can be treated.