memory

In depth

Three gestures

A memory always breaks down into three gestures: deciding what deserves to be written, deciding when to read it back, deciding what goes into the context. The third gesture is the only one the model perceives, since for it a memorised piece of information is indistinguishable from one you have just pasted in. The first is the most delicate, since it means settling what, in an exchange, counts as a lasting preference and what counts as a one-off. A badly sorted memory is not merely useless: it takes up the room and skews the answers that follow.

Several forms

Several forms coexist under the same word. Working memory keeps track of a task under way, session memory keeps the history of a conversation, durable memory retains facts or preferences from one time to the next. The boundary with document retrieval is thin and above all technical: both go and fetch a text to place it in front of the model, but one draws on what the system has observed of you, the other on a corpus assembled in advance. None of these forms modifies the model: memorising and retraining are two unrelated operations, one of them consultable and reversible, the other neither.

Three traps

Three traps recur. The first is legal and organisational: a memory is a database of users’ statements, subject to the same requirements as any other file, with a purpose, a retention period and a right to erasure. The second is expiry: a preference expressed once goes on applying long after it has ceased to be true, and no one can guess what has been retained if it is not displayed. The third is the hidden cost: memorising costs almost nothing, reading back is paid for, since everything placed in the context is billed at each request. A good memory is therefore judged as much by what it leaves out as by what it keeps.