Reason vs. emotion?

“The heart has its reasons, which reason knows nothing of,” wrote the French mathematician and philosopher Blaise Pascal (1623-1662). And indeed, many of the decisions that humans make cannot be explained or understood by reason – usually not even by the person who made them. Did the head decide, the gut, or something else entirely?

When a person thinks rationally about a problem, weighs up the pros and cons, or plans their future, they use the prefrontal cortex. This area of the brain is connected to the limbic system, the seat of emotions, and can control emotions – when it is reasonable to do so. The economic model of Homo economicus is based on the idea that every consumer thinks through the costs and benefits of their decisions purely rationally, and soberly attempts to maximize their profit. So, are humans purely rational beings controlled by their frontal lobe?

This model is now outdated: economists have simply overestimated the influence of rational decisions. No one acts purely rationally. Psychologist Gerd Gigerenzer from the Max Planck Institute for Human Development in Berlin puts it this way: “People make decisions – and now I'm going to say something radical, especially for us economists – mostly without calculating benefits and probabilities.”

For example, someone who blurts out “I quit!” to their boss in the heat of the moment has allowed themselves to be overwhelmed by their strong emotions. These emotions actually come, as the colloquial expression goes, partly from the gut (see info box). Such spontaneous emotional outbursts occur before one can properly identify the trigger (e.g., frustration with the boss) and the feeling. In fact, a mixture of feelings such as anger, guilt, disappointment, and sadness arise later.

A core area of the limbic system, the amygdala, fires especially when fear is involved, such as when there is a risk of losing something. In a study, Benedetto De Martino and his colleagues at University College London used magnetic resonance imaging (MRI) to look into the brains of test subjects who were offered £50 and given a choice: if they opted out at the beginning of the game, they would receive £20; if they continued playing, they could either win the entire £50 or walk away empty-handed. The interesting thing was that the way the question was phrased had a decisive influence on the subjects' decision. 62 percent chose to take the risk when they were told, “You will lose £30 if you don't play.” When told, “You can keep £20,” only 43 percent risked their luck.

Scientists refer to this as the framing effect: when the same fact is phrased differently, people often make different decisions. The reason: the threat of losing  £30 activates the amygdala and motivates people to take the risk – after all, otherwise they will lose something. However, the amygdala does not fire when it comes to the prospect of earning £20 for sure – even though the result for the wallet is exactly the same.

In addition to the amygdala, the reward system in the brain is also an early indicator of decisions. This includes, among other things, the nucleus accumbens. In an experiment, Brian Knutson of Stanford University offered his subjects chocolates for actual purchase in an MRI scanner. When the subjects reached for the chocolates, the nucleus accumbens was stimulated even before the subjects were aware that they were consenting. If the treat was too expensive, however, the insular cortex fired, obviously vetoing the purchase.

Emotions also set the tone when we perceive something as unfair. This was discovered in 2003 by a team led by Alan Sanfey, now at the Donders Institute for Brain, Cognition and Behavior at Radboud University Nijmegen. A player received a sum of money and had to decide how much of it to give to his fellow player. Only if the other player also accepted could both keep the money. If the person weighed up the situation purely rationally using the prefrontal cortex, the other player would always accept, because then they would ultimately receive money; if they refused, they would receive nothing at all.

However, many test subjects indignantly rejected unfair offers. This stimulated the insular cortex, cingulate gyrus, and prefrontal cortex in the brain. The researchers interpreted this as emotional conflict: the prefrontal cortex fired to overcome the negative feelings from the other two areas of the brain and persuade the test subjects to accept the unfair offer anyway. The prefrontal cortex therefore attempts to control and override emotions, but this does not always work.

The late brain researcher Gerhard Roth from the University of Bremen puts it even more radically: it is not reason that primarily guides our actions, but rather affects and emotions. This often happens unconsciously. “And so it happens that when asked, ‘Why did you just make that decision?’, we make something up because we simply have no access to our unconscious motives and impulses.” However, this does not mean that the mind cannot counteract this, said Roth. This tends to happen indirectly: the mind is only able to influence our plans for action by coupling opposing feelings. For example, if you feel like having chocolate spread for breakfast in the morning, even though you actually want to lose weight, reason can ensure that you leave the fatty food alone. According to Gerhard Roth, there are no rational decisions, only rational considerations.

But it's not always feelings that guide us, says psychologist Gerd Gigerenzer: Many “gut decisions” are often based on simple rules of thumb and experience that greatly simplify life. As an example, he cites the attempt to catch a ball: No one would calculate the ball's point of impact based on its trajectory, air resistance, wind direction, and so on. Instead, you fix your eyes on the ball and try to keep your angle of vision constant while running. This automatically reveals the position at which the ball must be caught. Even preschoolers have this “empirical knowledge” (intuitive physics), as they can effortlessly catch a ball rolling down an inclined plane without being able to explain why the ball must land exactly where they put their hand. But even buying the same brand of cat food every time, or deciding to follow the advice of close friends, is based on such experiential knowledge.

We are often not really aware of this experiential knowledge “because it is stored in a different data format, so to speak,” as Gerhard Roth says. However, it can be activated during decision-making, preferably while sleeping, or at least by temporarily switching off the mind: “Then all previous experiences are scanned, and they receive a kind of average assessment. This then manifests itself as a vague feeling, something like: Yes, I should do that,” says Roth. Especially when it comes to complex decisions, this form of intuition seems to be superior to rational consideration (see info box).
Intuition ha

probably saved many a cyclist from falling: When someone suddenly starts to skid on their bike, they intuitively decide to steer in the opposite direction based on their experience – without knowing the laws of physics or thinking through the consequences. However, if you ask people in advance what they would do in such a situation, they usually give completely wrong answers, the implementation of which would inevitably lead to a fall.

First published on February 20, 2012
Last updated on September 11, 2025