How reliable is our memory under conditions of stress?

In an earlier entry about false confessions, I briefly touched upon the topic of how memory works. The way it works barely resembles the way artificial memory systems work. Rather than accurately retrieving information, we reconstruct our memories every time we recall them.

The topic of memory, just like many other Psychology topics, is subjected to a lot of misconceptions and myths. The way we collect, store and recall memories is extremely complex with different factors like emotional activation or information type playing an important role.

How do emotions affect our memories?

It is a widespread idea that emotions have a strong effect on memory. As early as the inception of psychoanalysis, its proponents theorized that memories of traumatic experiences or emotionally disturbing events tended to be repressed. Despite the fact that repressed memories are still a popular concept, the actual incidence of repressed memories is very small. So much so, that many psychologists believe they should not be considered a real phenomenon.

Oddly enough, the belief that emotionally charged events are more memorable is also a common idea. So, what truth is there to these popular assumptions?


There is considerable scientific evidence that proves that information with emotional content is remembered more vividly than neutral information. [1] This happens not only with autobiographical memories – important events in our lives- but also with information provided in a lab in the course of an experiment.

Emotional information is remembered more accurately because of two special features that make its initial encoding more effective; valence and arousal. Emotional information, as opposed to neutral one, is evaluated by us as either positive or negative (valence). Emotional information also provides some type of physiological and psychological activation; having a soothing or agitating effect on us (arousal). Information is more effectively encoded when processed in this context of activation and interpretation as it helps us to combine new information with already existing memories.

Unreliable accounts

If emotionally charged memories seem to be remembered better than neutral ones, why are people so unreliable when retelling an emotional story?

Even though emotional events are generally remembered better than neutral ones, very intense emotional activation can make people forget details. Intense activation leads to attention narrowing which makes us focus on the central aspects of an event, ignoring the secondary details.

The Yerkes–Dodson curve; a classic, empirical law that dictates that performance increases with physiological or mental arousal, but only up to a point, can explain the difference in accuracy of memories on subjects under stress. When a certain point of activation is reached, performance decreases.

Yerkes-Dodson curve

The case of eyewitness testimony

The study of memory accuracy is of extreme importance to the field of Forensic Psychology. Eyewitness testimony plays a vital role in countless criminal investigations and court proceedings but the question that I get often times is; how reliable is eyewitness testimony?

Regarding eyewitnesses to a crime or accident, we should understand that they can vividly remember a given event and its most important features but; depending on their physiological activation, they won’t be able to give specific details about secondary aspects. Collateral information like the physical appearance of an aggressor or the color and size of certain objects won’t be stored accurately.

It seems to be the case that right after experiencing a traumatic event, only essential information is remembered. In the hours or days following the event, some secondary details and collateral information can be recovered and remembered.

The problem comes when an overzealous investigator questions a witness, providing details with their questions, which the subject can then incorporate into their own recollection, leading to inaccurate testimonies.

So in short, the accuracy of memories in the context of stressful events depends on:

  • The level of activation of the subject.
  • The amount of time that has elapsed since the event.
  • How the person is being questioned.

What could be done about this?

Interrogation techniques need to be refined. Not only police investigators need to formulate neutral and simple questions that don’t provide any information or opinion regarding the case. Also, the questioning by lawyers and prosecutors can alter a testimony, so they should be conducted carefully as well. When it comes to recognizing suspects, police lineups should be conducted similarly to how a scientific investigation, making use of double blinds and preventing anyone from giving any hints to the person doing the identification.

[1] Remembering emotional events. A. Burke (1992)


The hidden dangers of repeated head trauma

Earlier this year, Aaron Hernandez, an American football player, killed himself in his cell after being tried for a double murder. He was a rising football star when his legal issues first became public and many lamented how this put an end to what could have been an extraordinary career. Hernandez’s family decided to donate his brain to the CTE research center in Boston, with the intention to discover whether the athlete was affected by this neurological condition.

Although I have heard about Chronic traumatic encephalopathy before, it wasn’t until I read the news on Aaron Hernandez that I decided to delve into it. CTE is barely mentioned outside of the United States and I think that European sports authorities should be aware of the problem of repeated head trauma in players.


The consequences of repeated brain trauma amongst boxers are well documented. Dementia pugilistica -a subtype of CTE- has been studied since the late 1920s. Repeated head injuries in boxers can cause a pattern of neurodegeneration that produces dementia-like symptoms; cognitive and motor impairment, as well as mood and personality changes, which range in severity.

For many years, it was thought to only affect boxers, leading some medical professionals to ask for a ban on the sport. It is a recent discovery that repeated mild traumatic brain injuries increase the risk of neurodegenerative disease in athletes who play contact sports.

Although most research has been carried out in the context of American football, it is important to note that there are cases of CTE in many other sports; hockey, rugby, baseball, martial arts, soccer and motocross (BMX), as well as in people with military service.

Chronic traumatic encephalopathy usually manifests itself after about a decade of repeated injuries. Considering that many athletes begin their sports practice early on (ages 12 to 18), first-stage symptoms can be observed in young players in their early twenties [1]. Nevertheless, problems usually begin later in life.


CTE shouldn’t be confused with a post-concussion syndrome where symptoms are present shortly after a concussion but eventually go away. CTE consists in a progressive degeneration of the cortex and neuronal loss that, once it has been triggered, won’t stop in the individual’s lifetime. It has many similarities with Alzheimer’s and Parkinson’s disease, but in the case of CTE, we do know it has a clear environmental cause.

The diagnosis can only be confirmed post-mortem, once brain material is available to be examined. The research center I mentioned at the beginning of the article has examined the brain tissue of 94 former NFL players that presented symptoms and has concluded that 90 of them suffered from CTE. [2] Some of them had committed suicide at an early age, just like Aaron Hernandez did.

So, what can be done about this?

Since CTE is caused by recurrent concussions, the only way to prevent it, it’s by reducing the amount of exposure to head trauma. Unfortunately, that’s not an easy task. Sports-specific helmets seem to reduce injury in some sports. It is important to pay attention to the design and materials of the helmet as well as to make sure that it is replaced once it has taken a big hit.

Another very important factor is the “Return-to-play” criteria after a head injury. Studies suggest that a head injury should require at least 4 to 6 weeks of recovery time to avoid re-injury. Sadly, in some cases, these guidelines are not strictly enforced.

Lastly, athletes would benefit from some sports rules changes as well as from severe penalization for intentional hits to the head.


[1] Chronic Traumatic Encephalopathy in Athletes: Progressive Tauopathy following Repetitive Head Injury

[2] CTE Research Center Case Studies

The Psychology of False Confessions

Confessions have always been regarded as the best type of evidence that can be presented in a court of law. Centuries ago, a confession amounted to a conviction. Nowadays, the majority of criminal cases are solved by virtue of a confession, and jurors give a great importance to confession statements even when they are later retracted. The recent boom of true crime -with documentaries like Making a Murderer, Shadow of Truth or podcasts like Actual Innocence– has put the topic of false confessions in the spotlight.

It is very hard to assess the incidence of false confessions in a given country. The Innocent Project estimates that 25% of exonerees in the United States had confessed to the crime. Today I will like to take a look at the Psychology of false confessions, how and why do people confess to a crime they haven’t committed.

Types of false confessions

Before I begin, I will quickly touch on two types of false confessions that don’t need a lot of explanation. Firstly, we have the voluntary false confession. Voluntary confessions are common in very high-profile cases where someone confesses to a crime hoping to gain fame or recognition. Another type of voluntary false confession occurs when the person confessing is trying to protect the actual perpetrator. For instance, a mother trying to prevent her son from going to jail for killing her abusive husband.

The second type would be the coerced compliant confession. This confession is made by someone who has been forced to confess. The confession can be forced by means of physical violence or threats of being charged with other crimes if they don’t confess to the crime in question. It is important to note that in this instance, the subject is completely aware that they did not commit the crime and are just “cooperating” to avoid an adverse situation.

The third type of false confession is the most interesting one from a psychological point of view but also very unsettling to consider. It is called the coerced internalized confession. In this case, the person confessing to a crime they didn’t participate in, will eventually believe they committed such crime and their memory of the event in question can be altered forever.


How does a coerced internalized confession occur?

To understand this, we need to understand how human memory works. Human memory doesn’t work like computer memory, our memories are being transformed constantly. Every time we recall a stored memory, we reprocess it again and the end product -that we send back to storage- it’s something very similar to the original memory but with a few modifications. We introduce these modifications ourselves when we think about how that event unfolded. However, accounts from other people or information added by others can also change the way we remember said event.

The good news is that it takes a “perfect storm” of circumstances for a coerced internalized confession to happen, the bad news is that the most vulnerable people in our society are at risk.

The first factor we need to consider is how interrogations are carried out. Police interrogations are designed to deal with the “typical” criminal personality; extrovert, cunning, and extremely suspicious of law enforcement. When the same method is used on the opposite type of personality -introvert, gullible, and trusting of the police force- the suspect can feel easily overwhelmed and unable to cope with the stress of the interrogation.

Interrogations are usually long and conducted in a hostile environment with little sensory stimulation, no windows and only having contact with the investigators. The close, social interaction with the investigator, the uncertainty about one’s own safety and immediate situation as well as being confronted by an authority figure, make the suspect a very suggestible subject.

Investigators are allowed to present false evidence in the course of an interrogation. They can tell the accused they have DNA evidence, positive eyewitness identification or accomplice confessions. All this can be used as they please in the course of the interrogation in order to build their case. They are also allowed to use psychological manipulation; being on their side, minimizing the crime and its consequences or, conversely, maximizing them.

Suspects that finally succumb to these interrogation tactics and give a false confession have certain characteristics. Victims of false confessions are usually vulnerable people. Be it because of mental disability, low IQ, drug or alcohol use as well as withdrawal, fatigue or stress, they are put in a position where their memories are easily moldable. A low self-esteem, a lack of assertiveness as well as typically poor memory can also be determinant.

As the length of the interrogation grows, the suspect focus changes from long-term consequences (avoiding going to jail) to short-term consequences (being allowed to leave the stressful situation, resting or seeing and talking to their loved ones) so a coerced-internalized false confession is made. At this point, the highly suggestible subject has also started doubting that what he remembers is true and starts to believe the investigators’ version of events. This version has been repeated and reworked so many times that the accused has made it their own.

Final thoughts

The field of human memory research and false memories is fascinating one but I will not go into more depth today. I would like to see law enforcement being trained more adequately for suspect interrogations. A stronger focus should be placed on identifying and understanding a suspect’s shortcomings (like mental disability) in order to adapt their interrogation method.

It is clear that law enforcement methodology helps to solve many cases but in the cases in which their methodology elicits a false confession, the consequences are catastrophic. It is also important that we inform ourselves about the topic and in the case of ever serving on a jury, we should require more evidence than a confession to convict an accused person.

Source and recommended reading:

Gudjonsson, G. (2003). The psychology of interrogations and confessions.

How to be more confident

Many of us struggle with confidence. From deciding on a career path to having your voice being heard at the workplace or asking for a raise, a lack of confidence can have a bigger impact in our lives than we might think.

Although I won’t go into detail about what causes a lack of self-confidence, I would like to clarify that self-confidence is different from self-esteem and that they don’t necessarily go hand in hand. Self-confidence refers to the trust an individual has in their own abilities, whether they think they can rise to the occasion and be successful in a certain situation. Self-esteem refers to the appraisal of one’s own worth including appearance, emotions, and behaviors. It is possible to be self-confident and to have a low self-esteem (and vice versa).


A person with a healthy self-esteem can build their self-confidence through positive and successful experiences. I’d like to offer some ideas to start building your confidence.

1. Make a list of everything you have achieved in your life so far and you are proud of. We often forget or belittle the importance of our own accomplishments (graduating school, raising a child or a work anniversary). Achievements should be celebrated and seen as a demonstration of our own effort and abilities.

2. Come to terms with the fact that you are not perfect. You are -just like everyone else- good at some things and bad at others. Holding yourself to a very high standard and then failing to achieve it can result in low self-confidence.

3. Step outside of your comfort zone and get stuff done. Try attending a networking event or filing paperwork in person. Tackling these small tasks you dread can help you build your confidence as they will provide you with an instant feeling of achievement.

4. Take up something you are passionate about. For some people, it’s hard to feel efficient and accomplished when working in a competitive environment. For other people, it’s just the opposite and they feel that their current occupation it’s not challenging enough. Starting your own project or taking up a hobby can help you identify things you are good at, which will, in turn, make you feel more confident in your abilities.

5. Lastly: always allow yourself to make mistakes. Building self-confidence from experience also entails making mistakes and learning from them.

How does base rate bias work?

Cognitive biases are a very popular Psychology topic. I find them especially interesting because, in many cases, knowing about them and correctly identifying when we use them, can help us think more rationally and make better decisions.

Today I wanted to write about a type of bias that we often find in debates or opinionated conversations; the base rate bias or base rate fallacy.

The base rate bias occurs when base rate information is ignored and specific information -information relating to a certain case- is favored to make a judgment or reach a conclusion. Base rate information refers to the base probability of an event -also known as prior probability.

The base rate bias occurs when base rate information is ignored and specific information -information relating to a certain case- is favored to make a judgment or reach a conclusion. Base rate information refers to the base probability of an event -also known as prior probability.

I already talked about heuristics and cognitive biases and about how we still lack a coherent classification for them. Daniel Kahneman [1] considers base rate bias a specific form of extension neglect. Extension neglect occurs when the size of a set that is relevant to its valuation is disregarded.

The best way to understand this concept is by going over a couple of examples. The first one is a classic one and has been replicated many times with similar results. A group of participants is given the description of a fictional university student chosen at random. Consider Tom’s description:

“Tom is of high intelligence, although lacking in true creativity. He has a need for order and clarity, and for neat and tidy systems in which every detail finds its appropriate place. His writing is rather dull and mechanical. He has a strong drive for competence. He seems to have little feel and little sympathy for other people and does not enjoy interacting with others.” [2]

When asked about what program is Tom most likely to be attending, most people would reply ‘computational science’ or any other engineering program when, in fact, business and social science students are larger in number.

If Tom was chosen at random, he is more likely to be attending one of the most popular studies. Most people ignore this base rate information and reach a conclusion based on the fact that personality types like Tom seem more abundant in computational science programs.

Base rate bias and diagnosis


Another example that is often discussed is the base rate fallacy in diagnosis or assessing probabilities. Let’s assume that a certain disease manifests in 1 out of 1000 people, that means that a person has 0.10% chance of having that disease. There is a medical test that identifies 99% of positive cases when used on a sample of people who have the disease. That means that only 1% of positive cases are not diagnosed. Similarly, the test clears 99% of patients who do not have the disease and mistakenly diagnosis 1% of healthy individuals (false positive).

What is the probability of having the disease if the result of the test comes back positive? Not only patients but also most doctors would struggle to give a correct answer.

Making use of Bayesian statistics we can calculate the conditional probability:

p(disease | positive result) = p(disease) * p(positive result | disease) / p(positive result)

p(disease | positive result) = 0.001 * 0.99 / 0.001 * 0.99 + (1-0.001)*0.01 = 0.090 … 9%

This means that the probability of having the disease it is still 9% even with a positive result on the test. The reason being that the disease is very rare and only 0.10% of the population will have it.

Without making these calculations and considering the 99% of correct diagnosis, it is easy to think that the probability of being sick is much higher. This is why it is important to keep in mind the base rate information.


[1] Economic Preferences or Attitude Expressions?: An Analysis of Dollar Responses to Public Issues
[2] Kahneman, D., Slovic, P., & Tversky, A.E. 1982. Judgment under Uncertainty: Heuristics and Biases. Cambridge University Press.



How to beat winter blues

In my previous post, I talked about winter blues and how it differs from a seasonal affective disorder or winter depression. Because it is common to feel a bit down during the first quarter of the year, I wanted to give you some tips to overcome the winter blues.Keep your body active

Keep your body active

Extensive research seems to indicate that exercise not only improves physical health but also mental health [1]. It is not quite clear if there is a physiological mechanism responsible for this improvement. The positive effects could also come from a feeling of self-efficiency, distraction and -in some cases- the social interaction it promotes. Whatever the case may be, fitting in some exercise into your day, will have a positive impact on how you are feeling.


Interacting with people you like it’s a great way to overcome this gloomy season. It might seem hard but you should make an effort to accept invitations -even if you just stay for a while- as well as call up and set up dates with people you have been wanting to see for a while.

Don’t put too much on your plate

You need to incorporate all these new activities within reason. It is easy to feel overwhelmed by the New Year’s resolutions and goals you set for yourself for 2017. Try to find ways to keep yourself active by doing things you enjoy and that you really want to do. There is no need to sign up for spinning classes or have a dinner date every weeknight. Build up your routines gradually.

These were my three, very simple but effective tips to beat winter blues. I encourage you to put them into practice this week to start feeling better.



(This post was originally published on on January 22nd, 2017)