Part I: Background
Within four to five weeks, I’m going to let myself in with a prediction about whether machines will ever learn to read our minds, and I’m not quite sure what the confidence level of this prediction is. But hey, imagination is more important than knowlegde and I do have some insider arguments for what I will claim. So consider the current and upcoming posts as an invite to think about the subject yourself, and feel free to leave a comment if you have something interesting to add, if you’d like to ventilate your opinion, have some questions, …
Lately, there’s a lot to do about algorithms and machine learning. Will it ever destroy mankind, will it take over people’s jobs,… Many questions, but as the title suggests, this is not the one I’m interested in now. In the next couple of weeks, I will focus on whether machines will ever learn how to read our minds. I will do this by giving you a background, by explaining the most common stress monitoring techniques and we will finish off with a discussion and conclusion on the topic.
But why would machines even want to read our minds? In this paragraph we will look for the “why”. So let me ask you a question: suppose you’re going for a run and physically you feel well, but you just had a major setback at your work. Do you then run a PR? Probably not. Mental status has a significant effect on your performance. And this is only one example. Now, think of all people with a burn-out or depression. What if this could be detected in an early stage, and what if this causes the recovery duration to be cut in half? Wouldn’t that be a noble application of such technologies? Indeed! As you might have noticed, it’s not all scary, and it can bring big improvements to people’s lives.
So, where are we now? Well, it’s just 2018 and still many, many people are very busy trying to find out what on earth the brain is doing up there. Which means that there’s still a lot to discover. And just speaking between the lines: this is no more than common sense, but it’s a very important message to keep in mind, because throughout the series of upcomming blogposts I will guide you up to the point that this message starts making sense. How I do this? Well, let’s begin with the background.
There are multiple ways to monitor the mental status of an individual. In these series of blogposts, I will focus on the three most important:
- Skin conductance
- Heart rate variability (HRV)
- Decomposition of heart rate according to the energy equation
But before we really start digging into the methodologies itself, I would like to explain to you what happens in our body and mind when we are mentally aroused. Not in terms of psychology, but rather in terms of physiology. Being aroused simply means that there is an increase in physiological activity in our body. Here, I will focus on the stress reaction, no matter whether it is good (eustress) or bad (disstress). When someone is stressed for a presentation or because he/she is threatened by a criminal, the reaction of the body is quite similar. The body doesn’t distinguish between perceived and real stressors. Therefore, it’s possible to make a monitor for stress, based on the physiology of a stress reaction. Within the framework of the theory however, individual differences exist. For instance, some people will get very stressed out for a presentation, some people just a bit. Which means that the level of activity of the mechanisms that cause the arousal may differ between the two kinds of people, but not the mechanism itself.
So what are those mechanisms? Well, I could write an elaborate chapter in some stress-related book about it, but not everything is relevant for the stress-monitoring systems that will be discussed in the next weeks. Therefore, I will focus on what’s most important: the autonomic nervous system.
Actually, the autonomic nervous system is responsible for the change in variables that we measure with a stress-monitor. Simply put, the autonomic nervous system consists of two branches: the sympathetic and parasympathetic nervous system. Both have an influence on the variables we measure, however, in a different way. Most of us, probably have already heard of the fight-or-flight response. This is how we call the response of the body triggered by the sympathetic nervous system. However, it is not always a response as we see in the animal world, like when a prey gets chased by a predator and has the options to either flight or fight. When we humans give a presentation, the response of the sympathetic nervous system is the similar as in the animal, only we choose not to run or fight, because our mind knows it’s not necessary. But as said before, our body doesn’t differentiate between a perceived or real stressor and will make our hearts pumping faster, our breath being faster and more shallow, our sweat glands being more active,… In other words, we are ready to fight-or-flight.
But how does the sympathetic nervous system do this? Well, it’s mainly through the release of so called “catecholamines” in our brain. We know these substances better as adrenaline and noradrenaline. Through the release of catecholamines, a series of events takes place in several organ tissues and prepares our body to fight-or-flight. Several metabolic changes take place and we are ready for rapid physical movement. Please find a list below with the most relevant bodily changes caused by the sympathetic nervous system.
- Increased heart rate
- Increased ventilation
- Reduction of digestion
- Increased activity of the sweat glands
- Increased force of the muscles in the heart
- Widening of the arteries in the working muscles
- Constriction of the arteries in the muscles that are not working
- Widening of the pupils and bronchi (branches within the lungs)
It’s important to notice that this response is very fast and works immediately. However, when the stressor is gone, the body should calm down again. And that’s exactly what the parasympathetic nervous system is responsible for. You can visualize the sympathetic and parasympathetic nervous system as respectively the brake and gas pedal. They cannot have a dominant influence on the car (read: body) at the same time and both have their own influence. It’s quite logical actually, ever been relaxed and stressed at the same time? Exactly!
So how does the parasympathetic nervous system calm the body down? That’s mainly through the release of acetylcholine (ACh). It’s again an agent in the brain and causes the body to relax after a stressor and brings back the body in homeostasis (all functions of the body being in balance).
Now that we know the physiological background of stress, let’s go back to the stress monitoring systems, which are mainly algorithms coupled to or running in a piece of measurement hardware. Both the software and the hardware need each other, otherwise nothing would happen. First of all there is the monitor based on skin conductance. This methodology, that you often find in lie-detectors, is based on the theory that the resistance of the skin changes when the activity of the sweat glands changes. As we have seen before, increased sweating is part of the fight-or-flight response that is regulated by the sympathetic nervous system. Then, HRV. This is a theory that the variability in the interval between two consequetive heart beats, is related to the activity of the sympathetic and parasympathetic nervous system. And lastly, there is also a theory that heart rate is composed of different components that can be separated if you measure the right variables. One of these components is influenced by the mental status of an individual so if stress is a mental phenomenon (stress can also be physical!), then this component will be influenced by it. As you can see, the stress-monitors measure those variables that are infuenced by the autonomic nervous system at stressful moments. So it is key to measure variables that are somehow part of the stress response, simply because the thickness of your toe nail won’t tell you much.
Ok, let’s end here for today. I hope you now have a better idea of what’s happening in mind and body during stress and how it relates to stress-monitors. Next week’s blogpost will focus on: Stress monitoring via skin conductance.
This blog was originally posted here.