Thinking about happy memories might make you feel happy, but not all memories are pleasant. Some things are a bit  embarrassing, like that time i peed myself in 3rd grade. But, some unpleasant memories can be a lot more serious and traumatic. and you might even wish that you never had to remember a particular experience ever again.

That's the idea of the film “Eternal sunshine of the spotless mind” which is based on a line from 18th century poet Alexander Pope. Erasing certain memories might make you happier. It's more than just avoiding or suppressing a thought. You’d actually be incapable of remembering that thing anymore. It’s just gone, and even though scientists haven’t yet come up with a selective permanent delete button for memories. They probably could, someday.

It all has to do with how we forget things, and the fact that we seem to be able to do it on purpose. It’s easy to think of forgetting as a passive process. It’s not like you tried to forget where you put your keys yesterday. The passive kind of forgetting might be knowing the next time you’re trying to find your keys but it can also be useful for your brain. If you remembered everywhere you parked your car in the last month for example, you might get all confused when you were trying to figure out where you parked your car today. Was it by the fire station? no that was last week. the hotel? or was that yesterday. You see the problem here? This kind of passive forgetting isn’t really something you can control. But it turns out that there are active ways to forget things too.

It’s kind of like the opposite of memorization so researchers have been trying to test how that happens, because if we understand more about how it works, we might be able to control it. the thing is, studying humans is difficult, we’re unpredictable so it’s hard to get the same results every time. And studying memory is even harder. For one thing two people never have the same memory. Even of the same event. They’re seeing it from different perspectives and their brains are focusing on different things. That’s why psychologists have developed artificial psychology tests to use in studies. They help model how our memories work, but on a simpler scale, making results easier to replicated. One of those tests is called the think no think paradigm which is based on the idea that “Repeatedly stopping yourself from thinking about a memory should eventually force you to forget it”. It’s kind of counterintuitive, like i could have you try really hard not to imagine a purple elephant, but now all you’re thinking about is this purple elephant. Then again, you often have to practice something you do wanna remember, like your credit card number. So doing the opposite, practicing not thinking about it or making sure to think about other things might make you better at avoiding the memory. If you avoid it often enough, maybe you’ll eventually forget it. And this does seem to work.

In 2012, one group of American and British researchers published a study in the “Journal of Neuroscience” which monitored the brains of eighteen females while they did some memory tests. They used functional MRI to measure blood flow in the brain, more blood in one area generally means it’s more active. They found that the subjects were better at forgetting pairs of words they’d purposely tried not to think about than forgetting pairs of words they wanted to remember. Which seems to support this idea that we do have some level of control over what we remember. The researchers also found that when they were trying to remember a word pair, they showed more activity in the hippocampus, a region of the brain that helps with turning short-term memories into long term memories. And when they’d completely forgotten the word pair, the hippocampus didn’t show any change in activity at all. But when the subjects were trying to forget a word pair, they showed less activity in the hippocampus, but more activity in another part of the brain that’s associated with the hippocampus known as the dorsolateral prefrontal cortex or DLPFC for short. It’s involved in managing temporary memories but it’s also important for planning. So this region could be involved in the active forgetting process and it’s probably a good place to look to control that process. There are a couple things to keep in mind about this study though. First 18 subjects is not a lot of subjects. This needs to be tested more before we can call it conclusive. Second, words are just that. words. they’re nowhere near as complex as actual memories. We don’t know how much of what the researchers found applies to real life.

Another study published in 2013 in the “Journal of Experimental Psychology” tried to fix some of those issues by studying personal memories. The 60 college students were told to associate certain pairs of words with happy or unhappy memories, and the researchers recorded how many details of those memories they could remember. Then once the subjects had memories which memory went with each word pair, the team showed them the word pairs and either told them to actively think about the memory or try not to think about it. Afterwords, the students were told to describe the details of the memories again, but they couldn’t remember as much from the memories they tried to forget. They didn’t forget the entire event or anything but might have something to do with the fact that the experiment only lasted a week.

So, we know that actively trying to forget things like word pairs involve more activity in certain regions of the brain, and less activity in others. We also know that similar techniques work if you wanna forget more complex memories, like those of events. The next step would be to try to identify some of the proteins, and the genes that control them, involved in active forgetting. Which is why some researchers are studying the genes that control memory using a type of tiny worm known as “C elegans”. In 2014, a group of Swiss and Hungarian researchers published the results of a study in the journal “Cell”. They trained different groups of worms to understand that if they crawled toward or away from a specific smell, they would find food. But some of the worms had a particular gene known as “musashi”, turned off. And they remembered the smell cue longer than the rest of the worms. This makes sense cause “musashi” controls how cells make a protein that helps with reshaping the paths neurons used to transmit information. The thinking goes, if the pathways can’t change, the worms don’t forget.

Then, in a study published in the journal “Nature Communications” in august, a team of neuroscientists tried to block the emotions associated with rat memories by interfering with certain genes. They based their experiment on the idea that sometimes you, or the researcher might learn to fear something, like taking a really difficult test. So the next time you take a test, it turns out to be super easy for you and the next one, and the next. Eventually, you might even forget that you used to be scared of taking tests. That is, until you sit down for the final exam and the first question is so complicated that you don’t even understand what the teacher is asking. But what if you turned off the genes that control the processes in your brain that remind you to be afraid of the test. Well the researchers tried to figure that out by studying rats which were placed in a cage and given a small foot shock. They were taken out of the cage, but then put back, this time, without any foot shocks. Basically, they were training the rats to not be afraid anymore. Then the team gave some of the rats a drug that would limit the activity of a gene called “ARC”, which is associated with long-term memory formation. When these rats were given another small foot shock, enough to trigger the memory of fear, but not enough to teach them to be afraid all over again, they still weren’t showing signs of fear. We, humans, share some of our genes with worms and rats, and we have our own versions of “Musashi” and “ARC” for example. So, these types of studies could help researchers build a forget button for humans too.

Knowing what genes are important for a process, whether it be forgetting a memory or increasing your risk for developing a disease, is useful for scientists in trying to understand how to change that process. So, with more research, we might eventually learn how to control which memories we forget. But, if you could permanently completely forget certain memories, would you actually want to? Right now, even the most advanced forgetting techniques can’t completely eliminate a memory. They just help you remember fewer details, or associate the memory with less intense emotions. But if we could force ourselves to completely forget, there would be a lot of ethical and moral questions to address. I mean, for all we know, forgetting a memory would change who you are as a person. And, purposely forgetting a crime you committed or just witnessed, would be a big problem for the legal system, and even if we can reliably make ourselves forget, who gets to decide what memories we remember?

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