Episodic memory is a form of explicit memory, which means that you have to consciously remember episodic events. It’s essentially the type of memories that come from your own life that you can explicitly tell other people about. With your episodic memory, your mind can basically form its own time machine and travel back in time. Depending on how well you remember things, you may be able to travel all the way back to your earliest memories and tell other people about them as if you were really there.
One interesting thing about episodic memory is that it’s firmly rooted in time and context. For instance, you might remember a purple shirt you got for Christmas when you were little because you see the color purple at a store you like now. The current situation triggered the older memory because you associated the color purple with that particular memory.
When we say that episodic memory is rooted in time, we don’t mean that you have to have a specific time in mind for every episodic memory. This ability to specifically date stamp memories is rare except when it comes to your major memories that are inherently linked to dates – like your wedding day. Instead, you’re more likely to hear people tell about their episodic memories by saying things like “when I was about five” or “that year that it was so hot all summer that all the grass dried up.”
These are still time cues; they just aren’t specific. They still give your memories structure, and you can often figure out exactly when they happened by talking these memories over with other people who share your past, since other people might remember if you were four or five when you broke your arm or exactly which summer it was that the grass got so dry.
Episodic memory, which is a form of explicit memory, is also linked to semantic memory, a form of implicit – or subconscious – memory. Semantic memory basically gives you a map of the things you’ve learned, including essential concepts (like what a dog is) and skills (like how to spell certain words). Episodic memories essentially make up your semantic memories, even though you don’t think about it this way.
For instance, when you read the word “fish” what do you think of? I, for one, think of something slightly slimy with scales, gills, and bulgy eyes. I know some fish, like the red beta fish I had in high school, are really pretty and graceful, but others, like the catfish I caught but was afraid to touch when I was six, are really ugly and gross looking. Your semantic idea of “fish” might be somewhat different from mine, but we still both know what a fish is.
Now, where does this generalized concept of “fish” come from? It doesn’t come from a dictionary definition! Instead, it came from all my episodic memories that involve fish, whether I was reading about them, eating them, catching them, or keeping them as pets. Without all those episodic memories, my idea of what “fish” means – my semantic memory of the word and concept “fish” – would be much more vague.
So, you can see how our memories are super complex and work together on many different levels to form the memories that we use every day and the memories that make us who we are. Without your episodic memory – the memories of your life – you wouldn’t know your own history, which is what makes amnesia and Alzheimer’s so tragic. But without episodic memory, you also wouldn’t have the semantic memories that give you the ability to operate your life in the real world.