seems the script writers got two different (but possibly similar sounding) types of mnemonic confused.

an example of remembering something associatively might be - say for example I am trying to remember the artist of a painting I like but it isn't coming to mind. I think of the information i do know (movement, other artists, time period) in order to trigger the memory.

about roman room - which is what watson is describing
(imagining a house or place and depositing bit of info/memory there:

about using mind mapping (a way to memorize and then retrieve associatively)

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