This sounds like a bizarre question. Memory is a pretty fundamental word we all use in our daily lives. But it’s a word that carries a lot of significance in the field of computer science – in particular the field of artificial intelligence. I use it. Often. And usually pretty haphazardly. At the encouragement of others within my department, I’ve been convinced to read a bit more about the psychology / neurology roots of the word. Actually … I should restate that. I have no idea what the etymology of “memory” is. I’m guessing it’s rooted in psychology. And then neurology. So I include those. But I’m sure there’s more fields to look at when studying the definition of the word. I digress ….

I thought before I dove into looking up how these fields view “memory” I should document what I refer to when using the word.

I admit, that my usage is likely fairly naive. When I refer to “memory” it’s generally in the context of a reinforcement learning agent. And it usually loosely means, information, that is from the past, that is available to the agent at the current time-step. So previous observations are memory. Traces are memory. Anything that encapsulates past information is “memory.” hmm. that’s about it. But I realize that is I poor definition. By that definition, a value function is “memory.” It encapsulates information from the past, and makes it available to the agent at the current time step. But that’s clearly not what I mean. So I need to go further. “Memory” to me, is more raw than a general value function. It’s close to an original observation from the past, available in the current time. But that’s not quite right either. I leave a little bit of wiggle room to massage the original observation into a representation available for the current step (but not massaged into a value function).

So there you have it. An incredibly lackluster and flawed definition. I’ll intentionally leave it at that for this post. (I think the point of studying the etymology of “memory” is not only to not annoy psychologists/neurologists by my usage of the term – but to inspire and motivate work within AI.)