The Unreliability of Memory

There is something that you are guilty of, no matter how much you might deny it. That thing is that your memory is like Lego. Many people like to think of memory as a tape recorder where everything that goes in can be accessed exactly how it was. But, as you may have guessed, this is not the case. The truth is, memories are reconstructed every time you recall them. And, like rebuilding a Lego tower, they change.

Usually this unreliability is acceptable. However, as soon as you introduce anything that relies on memory to provide the solution, credibility quickly degrades. This is seen often in witness testimonies. See, court is a tricky place. It’s where important decisions are made. People are condemned, people are set free and sometimes, the innocent lose everything. A study in 1987 by professor of criminal Justice C.R. Huff looked at 500 wrongful convictions and found that 60% of these convictions were due to faulty eyewitnesses. Yale Law Professor Edwin Borchard studied 65 wrongful convictions and also found that faulty eyewitness was a leading factorThe trouble with eyewitnesses is that they rely on memory and the trouble with memory is that it’s subjective. We can remember what was emotionally important at the time but trivial things seem to disappear. So if the witness was in a rush or if the lighting was bad then there may be flaws in what they can remember. Unreliable judgement results in an unreliable accusation. A study done at Northwestern University shows that when the brain has heightened activity, it will not play back a memory until the mind returns to the state in which that memory was first encoded.

If someone is witnessing a crime, they are undoubtedly under stress. Stress can sharpen the senses but it also allows us to focus only on what is important at the time, for example a gun and not the gunman’s face. Stress actually does a couple things when it comes to memory and neither of them deserve a medal. First, it stops the brain from encoding information. Whenever something happens, it goes straight to our short term memory. Then over time, we transfer that information into our long-term where it can stay for seemingly forever. What stress does is it gets in the way so that we can’t store that memory in our long-term and essentially, we lose it. Secondly, stress makes it awfully difficult to retrieve a memory. So, let’s say someone just got shot and the police are all around you. Chances are, you’re going to make up something that sounds good and get the heck out of there. And let’s say there are multiple perpetrators. Had trouble remembering one face? Have fun remembering several.

The second problem with memory is that a lot of it is based on assumptions. Pieces are filled in as we learn new information. And we’re always learning new information. Every single witness will be influenced; by each other, by the news. The mind fills in missing pieces and combines memories into new ones.  Memory is malleable and even word choice can change it. For example, if I ask you if you’ve seen a stop sign, you might say yes or no. But if I say did you see the stop sign, you’ll be more tempted to say yes. Why? Because the word ‘the’ implies that there was a stop sign there and that you should have seen it.A while back in 1974, memory researchers and psychologists, Elizabeth Loftus, and John Palmer got a group of people to watch a film of a traffic accident. They then asked them what they had seen using two different words, smash and hit. The word smash evoked higher estimates in speed as well as convinced people that there was broken glass in the film when there wasn’t. So low and behold, the way you phrase a question can change a memory. Loftus has also published several other studies, one of which shows that because descriptions of suspects can influence eyewitnesses, their ability to identify a suspect from a photo is not reliable.

The final major effect of faulty memory is time. Let’s take this blog post for example. Immediately after you read it, if you were paying attention of course, you could probably summarize what the post was about. However next week or next year? Most people need to wait a very long time for their trial; sometimes up to several years. By that time, they will have heard stories from other people and probably accessed the memory several hundred times. An experiment done on short term memory in 1959 by Peterson and Peterson had participants memorize a three letter sequence. They then counted backwards before trying to recall the sequence after varying lengths of time. After only six seconds, half of the original three letters were forgotten. After 18 seconds, the memory was completely gone. This shows that anything in your short term memory vanishes very quickly. In order to store it in your long term, the information must often be repeated, such as saying a license plate number to yourself over and over. However, this process is quite prone to failure if interrupted. As for long term memory, not much is known about it. Some scientists believe that memories can remain there indefinitely and that it is a matter of recalling them that can be the issue.

Recall, or ‘remembering’  is the process of re-accessing the information stored in our brains. Whenever we recall a memory, we are building it up again; remember the Lego? We take the memory out of long term, access it and then put it back. Because of this, the longer we have to go over the memory, even just in our own minds, the longer we have to reprocess it and screw up the details. Note that in court, details are very important. Memory is also almost always activated after a stimulus. Because of this, it can be quite beneficial to bring the witness back to the environment in which the crime first happened.
So, we have looked at how subjectivity, influence and time affect the reliability of witness’ memories. In many courts it is now a standard to educate the jury on the malleability of memory. Expert psychologists oversee the trial and most sentences need hard evidence to support them. However, even experts cannot gauge the credibility of a memory and the innocent may all but lose their lives. It is important to know that although Lego can be useful, you should never use it to support a trial.


Have you had experience with forgetting (don’t lie)? Have you ever been to court or heard about a trial in which someone was falsely accused? Do you think that witness testimony should be important in making decisions by the jury or are there better ways to go about sentencing people?