Emotions affect rational decisions.

In Britain, the average adult spends approximately £144,000 ($177,000) on impulse purchase over their lifetime [1]. Undoubtedly, emotions play a significant role in impulse purchases. So, should we use pure logic when buying chocolate? Maybe, but what if emotions also interfere with rational decisions? Here is a glimpse on how neuroscience and innovation explain individual differences of emotional responses, and how these feelings affect our rational decision-making process.

Antonio Damasio, a Portuguese neuroscientist, is the author of numerous scientific articles and books, one of which I present on this post; Descartes’ Error (1994). I focus on Chapter 8, The Somatic Marker Hypothesis, which builds on my previous post on the neural processing of fear. Nonetheless, the book marks a shift in neuroscience research; now, emotions play a central role in cognitive skills, such as decision-making. As a consequence, the science of emotions develops as a branch of modern cognitive neuroscience.

A brief context

The mind-body problem refers to a theoretical inconsistency whereby consciousness is part of the mind but separate from the brain, which is a physical structure of the body. René Descartes (1596-1650) a French philosopher known for his quote “I think, therefore, I am” decided to tackle the mind-body problem. He proposed that the mind and body were two, distinct substances—also known as the Cartesian dualism. However, as you can imagine, the 17th-century biomedical science had several limitations. Thus, leading him to false conclusions about the mind-body problem. Hence, Descartes’ error. 

Reasoning and decision

The purpose of reasoning is to make a decision. Decisions involve selecting a response, a word, a sentence, or a non-verbal action among many possibilities available at the moment. Moreover, reasoning implies that the individual is aware of the situation, different responses, and consequence and outcome both in the present and future. The brain supports the decision mechanism by (a) making memory accessible in both verbal and visual forms, almost immediately, (b) increasing attention and (c) creating motivation through emotions and feelings.

However, different decisions have different effects on the body. For example, a car speeding in your direction elicits a quick decision (e.g. jump back and avoid getting hit) and triggers bodily reactions (e.g. stress), which you can read more about it here. Similarly, deciding whom to ask on a date or which candidate to vote for, demands a particular set of biological and neurological mechanisms. 

Moreover, both attention span and working memory (i.e. ability to hold in mind a piece of information for a few seconds, such as a phone number) have limited capacity. Thus, it is unrealistic to calculate all possible outcomes before making a rational decision. Our brains manage to come up with a decision in a time frame appropriate to each circumstance. Therefore, Damasio explains that emotions play an essential role in decision making.

The Somatic Marker Hypothesis 

The somatic marker hypothesis explains the neuropsychological role of emotions in practical decision making. The word soma is Greek for the body, and as emotional effects ‘mark’ changes in the body, Damasio has called them somatic markers. 

More specifically, the somatic markers hypothesis refers to emotional reactions with a strong body component supporting each decision making, including rational decisions. Some of these reactions include physiological changes, such as heart rate, blood pressure, skin conductance, pupil size. Interestingly, these measures provide a robust indication of anxiety, stress and fear, which involves the amygdala (I have covered the basics of fear and stress as well as the types of stress).

A real-life example

These reactions stem from your previous experiences in similar situations. For example, somatic markers enable quick comparison of the relevant alternatives. Then, these alternatives are subjected to further cognitive processing before the final decision.

Imagine the following scenario; you have just arrived in a city for the first time, and you find yourself lost in the middle of nowhere. As you reach your smartphone to request a ride on Uber, you realise your mobile battery is dead. This means you have to think and make a decision on how to get to the hotel. Based on the somatic marker hypothesis, the intensity of your stress and fear depends on your brain’s evaluation of the previous situation in which you were lost. It may include childhood memories as well as memories from recent trips.

Therefore, more experience indicates quicker and less stressful decisions. Consequently, it is not surprising to see experienced actors improvising brilliantly, whereas acting students might cry on stage. These neuropsychological and bodily processes increase the accuracy as well as the efficiency of human decision-making. 

Food for thought

Now, we take a step further and put the somatic marker hypothesis into action. Reasoning about a problem depends both on one’s innate sensitivity to stressors and the process of education and socialisation. This combination indicates that one’s experience under the control of external factors (e.g. parents, school and culture) produce different somatic markers.

Moreover, the brain’s primary responsibility is to ensure survival, which is the reason we get stressed, fear the unknown, and avoid pain. Our neural basis disposes of an innate adverse reaction to anything that causes pain. Therefore, we are biased to avoid things we dislike. Children who grew up in different environments may feel different in similar situations. 

For example, how do you feel about eating corn on the cob, OK? Now, how do you feel about drinking a smoothie made from corn kernels, milk and sugar? Do you feel disgusted? Having a corn smoothie is quite common in Brazil, but no elsewhere. This example illustrates how people make decisions based on different emotions associated with the same thing.

Interestingly enough, the idea of a corn smoothie evoked the feeling of disgust. Therefore, your thoughts create emotions, which, in turn, affect your decisions. Watch out for that! 

There is a biased system that we should be aware of before criticising other people. Thus, to avoid unnecessary conflict, we should rely on research-based and peer-reviewed facts as part of critical thinking.


Now you have the opportunity to take your understanding of the somatic marker hypothesis and decision-making process to the next level. 

For instance, think how your biased neural and physiological mechanism, which receives early input from culture and environment affects your opinion on complex social issues? For example, how do you feel about the abortion debate?

Make a list of factors driving your opinion. Then, make a list of feelings that you have about abortion. Interestingly, notice how some counterarguments may trigger negative emotions on you. Nevertheless, these counterarguments are not necessarily false.


The somatic marker hypothesis explains the neuropsychological influence of emotions in our decision-making process, including rational decisions. Moreover, our brain evolved an innate bias against pain as a survival mechanism. As a consequence, social and external influences create contrasting views about similar topics, food and political issues. Thus, critical thinking and science-based facts support evaluating complex decisions. 

Interact and find out more!

Let me know how you felt after reading this post? Also, share your thoughts, trying to put aside your emotions. Share with friends and colleagues and hear how they feel about it.

If you would like to read Descartes’ Error, then you can easily buy it on Amazon. Also, subscribe for more on Neuroscience and innovation, and follow me on Instagram for exclusive content.


[1] Hall, A. (2018, January 15). Brits spend £144,000 on ‘impulse buys’ during lifetime, research finds. Retrieved from The Independent.

[2] Damasio, A. R. (2006). Descartes’ error. Random House.

Image by Thuong Do

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