The somatic marker hypothesis can explain the role of emotions in practical reasoning.

Let’s end by returning to our final question: What role do secondary emotions play in our practical reasoning?

We’ve been pursuing a mystery in which the main suspects are the limbic system, the somatosensory cortex, and the ventromedial prefrontal cortex. If you were hoping the answer would have a more melodious name, you’re going to be disappointed. It’s called the somatic marker hypothesis – but it’s a lot more interesting than it sounds!

Somatic markers are a special type of secondary emotion that plays a key role in our decision-making processes. Basically, as you think through all of your options and their possible outcomes, you feel secondary emotions about each of them. Depending on whether the emotions are positive or negative, they steer you toward or away from certain options. The emotions help you “mark out” your options – saying “go this way” or “don’t go that way.”

For example, let’s say you find yourself in a situation like Elliot’s. You’re trying to choose between scheduling an appointment on Monday or Wednesday. Now, imagine you’ve come to hate having appointments on Mondays. Maybe the combination of going back to work and attending an appointment on the same day has a history of stressing you out.

All of this life experience is baked into a negative secondary emotion you’ve developed toward Mondays. If you analyzed it, you’d find some very useful information about yourself and the option in question. But you don’t need to waste time thinking through all of that information. Instead, you just feel an almost instantaneous negative gut feeling toward the prospect of scheduling the appointment on Monday. A couple of seconds later, you choose Wednesday. Your decision is done.

In contrast, when Elliot tries to make this decision, he doesn’t have the luxury of somatic markers saying, “go this way” or “go that way.” As a result, he ends up wandering around the landscape of possibilities in front of him, exploring every nook and cranny. What if it rains on Monday? What if there’s traffic on Wednesday? The questions go on and on.

But the world doesn’t wait for us to ponder them. Life keeps throwing choices at us, and our brains need to make reasonable decisions in reasonable amounts of time. To do this, they need the help of the somatic markers provided by our secondary emotions.

To sum up: in order to be reasonable, our brains need to listen to our bodies and the emotions they express. Reason and emotion. Brain and body. Rather than being at odds with each other, they depend on one another. They need to work together. Otherwise, we end up like Elliot – lost in a wilderness of endless possibilities.