What happens when you know you know something?

29 September 2015



Hi Chris I actually emailed in with a question for you guys in my first year at uni here in Nottingham studying neuroscience, so its quite fitting that I felt the need to ask another just as I'm set to graduate. In terms of my limited understanding of how memory works, it seems that through LTP and other mechanisms you can physically strengthen a synapse to make a stronger memory. However, what exactly is going on at a basic structural level in these two examples: How is it that you can be told something (e.g. 'fact x') and be aware you have been told it before (the accompanying phrase usually being "oh yeah, I knew that"). Yet you wouldn't have been able to state the fact alone. Similarly, when asked a question, how can you find yourself saying "I know it, I just can't remember it", since this seems to imply you have consolidated the memory of learning the fact, without consolidating the fact itself. This particular example making an all too regular appearance at any pub quiz I've ever attended. I'm afraid it was incredibly hard to try and word this question clearly but I hope the phrases as examples make it easier to understand thanks very much! Dominic Parker


We put Dominic's question to brain-expert Ginny Smith...

Ginny - There's actually probably two different things going on there. So the first one is what we call the tip of the tongue phenomenon which is this idea that you can have something in mind and you feel like you know what it is, but you just can't quite retrieve it. And it's really, really common and it can be more common in older people. It's more common if you get tired. That all suggests that there's something that's not quite working properly in your brain. We lay down memories and they're stored but then to access them, we need to activate the neural pathway that was laid down. Sometimes that can be difficult. We're not quite sure why it does sometimes go wrong, but one theory is that the tip of the tongue phenomenon happens when the answer is in your brain and you just can't retrieve it. There's another idea which actually gives you a little bit less credit which is that you don't actually know it. You just think you do. So, it could be that something in the question itself has triggered this sense of familiarity and then you misattribute that to you knowing the answer. And actually, it wasn't even in your brain to start with. So we're not sure which one of those is true. The second part of the question is that feeling of, "Oh! Of course, I knew that." Again, that's a nice little trick that our brain plays on us. We like to think that we're clever and we know a lot of things. Chances are, you never knew it was Kylie Minogue. It's much easier to recognise things than it is to recall them. So, it sounds about right once it's being said and that sense of familiarity of, "Oh, yeah that sounds plausible" your brain can misconstrue that and make you think that you actually knew it when chances are, you didn't....


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