Retrieving Long-Term Memories: Interference, Amnesia & State-Dependent Memory

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  • 0:04 Retrieval
  • 0:59 Interference
  • 3:36 State-Dependent Memory
  • 6:45 Amnesia
  • 11:25 Summary
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Lesson Transcript
Instructor: Wind Goodfriend
Have you ever been sure that you know something but simply can't pull it out of your memory? This frustrating experience is a lack of retrieval, and this lesson discusses several aspects of successful retrieval, including retroactive and proactive interference, state-dependent memory and different forms of amnesia.


We've all experienced the frustration of trying to remember something we know is in our memory, but for some reason we just can't access it. You might have said, 'It's on the tip of my tongue!' Maybe you were taking a test, and you were trying to list all the capitals in Europe, but for some reason, the capital of Spain is just blocked! You sit there, getting more and more upset, but eventually turn in your test without the answer. As soon as you walk out of the room, it hits you: Madrid! The information was in your mind, but for some reason you couldn't get to the information.

Successfully accessing information stored in our long-term memory is called retrieval. Theoretically, once something has been encoded and stored into long term memory, it's there for permanent use. So, why would our memories sometimes fail us? This lesson covers many possible reasons why retrieval might be blocked, as well as a couple of ideas on how to improve retrieval.


The first problem with memory we'll discuss today is called interference. This is a problem that can cause your memory difficulty on the front end, when the memory is first being formed. Imagine that you're in history class, and you're learning about the U.S. presidents. First, you learn about Washington, then Adams, then Jefferson... You're trying to pay attention and remember the details about each person, but by the time you get to Madison, you're starting to get them mixed up.

The problem you're experiencing is called proactive interference. Proactive interference occurs when previously learned information, such as learning about the first president, interferes with new information that you're trying to learn. The previous information is already there, taking up space in your working memory, so any new information has to compete. In this example, you would probably have a pretty good memory for the information about Washington because there was nothing else to distract you. But, as each person got added to the list, you would get more and more confused as you try to learn new information.

The opposite problem can also occur. Let's go back to the idea of studying the U.S. presidents. You're reading a magazine article about President Obama in which you hear about recent changes he's made to the White House furniture. Later, you're having a conversation with your friend about the history of the White House, and you get confused regarding which President made which changes. You mistakenly state that Reagan reupholstered the dining room chairs, when really Obama is the one who did that. Before you read the Obama article, you knew all about Reagan and wouldn't have made this mistake.

What happened to you in this example is that newly acquired information made it more difficult for you to remember previously acquired information. This problem is called retroactive interference. You learning new information has gotten mixed up with old information you had, making it more difficult to remember the old information.

So, just to be clear, let's go over the difference between the two types of interference. With proactive interference, old information makes it harder to learn new information. So, knowing about President Washington already makes it harder for you to learn new information about later presidents. But with retroactive interference, new information makes it harder for you to remember old information. The fact that you just learned something about President Obama made you get confused about what you had already learned about President Reagan, so the problem occurred in the opposite direction.

Either type of interference can cause you to make memory mistakes when you're trying to retrieve information. The best way to get around the problem of interference is to make sure you take lots of breaks when you are studying so that your mind is fresh when you approach the new topic.

State-Dependent Memory

Another way that memory can be helped or hurt is something called state-dependent memory. To understand this idea, let me tell you a quick story. I work at a university. One day I was in the grocery store, and I saw a woman I knew I was supposed to recognize, but I just couldn't figure out who she was. I finally realized that it was a woman who works in the Human Resources office of my university, but I had never seen her outside of that office before. It was strange to see her in a different place, and being in the grocery store made it harder for me to recognize her.

Has this kind of thing ever happened to you? If so, it's an example of state-dependent memory. State-dependent memory is when memory retrieval is improved when the environment for encoding is the same as the environment for retrieval. In other words, if you're in the same place when you're trying to use the memory as you were when you first created the memory, your memory will work better. If you're in a different place, your memory might be blocked. Let's go through a couple of other examples.

When you sit in a classroom, you probably have a favorite chair or place you like to sit. Do you like to be in the front row center because you feel like it's the best way to stay focused? Or do you like to sit more near the back, so you're less likely to be called on by the teacher? Either way, we tend to pick a chair on the first day and then sit in the same chair for the rest of the class. That's partially due to simple habit or preferences, but that tendency also helps our memories. If we sit in a certain chair when we learn information in a class, we're more likely to remember that information when we take the test if we're sitting in the exact same place in the classroom. If we have to move, being in that slightly different environment can actually mess up our memories and make retrieval harder. You can use this information the next time you're studying. If you have the classroom available, study in the chair where you'll be taking the test. It might help!

So far, the examples we've gone over in state-dependent memory have been about physical places, such as an office at work or a particular chair in a classroom. But state-dependent memory can refer to a physical state or location like this, or it can refer to a mental state. If you make certain memories when you're happy or in a good mood, then you're more likely to remember those events later when you're in the same mood. This is also true of mental states that are altered, such as being intoxicated. If you were drunk when you learned a certain fact, you'll probably have trouble remembering that fact the next day when you're sober. But if you get drunk again that night, the information might suddenly come back to you!

Why does state-dependent memory happen? Research says it's because when you initially form a new memory, part of that experience is everything that was happening around you, such as where you were or what mood you were in. So, those environmental things are also tied to the memory. Anything that reminds you of that event is called a retrieval cue. The more reminders, or retrieval cues, you have of a certain memory, the more likely it is that you'll be able to successfully retrieve it later. So, being in the same location or state of mind is a good way to help improve your memory.


Maybe the most famous type of forgetting is in people who have amnesia. Amnesia has been the subject of lots of TV shows and movies. But what's the truth about how amnesia works and how it relates to retrieval of memories? In all forms of amnesia, there's some kind of problem with memory retrieval. There are three basic types of amnesia. Let's talk about each type.

The first type is probably the most famous; it's called dissociative amnesia. Dissociative amnesia occurs because someone experiences something that is psychologically traumatic or stressful. That event is so stressful that the person unconsciously blocks all biographical information about him or herself, as a way of avoiding the painful memory. Instead of just forgetting the single memory, which would be called repression, with dissociative amnesia, a person's biographical history is removed from the mind as a way of removing the painful memory. The person might lose his or her entire life's history or it might just be parts that are relevant to the traumatic event. Even though dissociative amnesia is the subject of lots of movies and TV shows, in real life it is extremely rare.

While dissociative amnesia is caused by psychological trauma, the other two major types of amnesia are both caused by physical problems, and therefore, they are much more common. The types of problems you might experience to get a physical form of amnesia might be a car accident, a blunt trauma to the head or certain diseases that cause damage to the neurons in your brain.

The first type is called retrograde amnesia. With retrograde amnesia, a person loses memories for a period of time before the physical damage occurred. In other words, let's say you experience a head trauma - the time period right before that event will be lost from your memory. You can remember the term 'retrograde' because the term 'retro' means going back in time, like wearing 'retro' clothes from the 1970s. With retrograde amnesia, you lose memories from your past.

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