Does the heart rule the mind?

gzlaser

SOMETIMES we are forced to make a decision when we feel ourselves pulled in opposite directions by reason and emotion. Our head tells us to do one thing, but our heart says do the other.

For the first time in history we are getting close to answering the question of whether the heart rules the head, thanks to an innovation called functional magnetic-resonance imaging, or fMRI.

This technology allows scientists to measure the level of oxygen in the blood, and tells them which parts of the brain are most active. It can show, for example, the parts of the brain that operate when we fall in love or when we feel like eating a particular type of food. It recently revealed the differences in the brains of Democrat and Republican voters in the US elections.

The new technology also holds the promise of answering questions about our deepest human characteristics. For example, do we have an inbuilt moral sense, or do we learn what is right and wrong as we grow up? And which is stronger, emotion or logic?

No trauma

Before fMRI, information on the parts of the brain involved in different tasks could only be gathered by studying people who had suffered brain damage from trauma or stroke, and seeing how their brain functions changed. Now, the brains of healthy people can be scanned as they are performing different tasks.

\"FMRI has provided striking evidence in favour of some theories, and against others,\" said Joshua Greene, of Princeton University's department of psychology, in the US.

Greene, together with Jonathan Cohen, professor of psychology at Princeton, is using fMRI to look at the factors that influence moral judgment.

To do so, the researchers scan the brains of volunteers while asking them tricky questions. For example, imagine you and your neighbours are hiding in a cellar from enemy soldiers. Your baby starts to cry. If he continues, the soldiers will discover your hiding place and kill you all. The only way to save yourself and the others is to silence your baby — by smothering him to death. What do you do?

Clearly, you would feel intense emotions, and this shows on the brain scan.

But you would also be forced to make a logical assessment of the situation, and this shows up on the brain scan too. Areas involved in abstract reasoning and those that process emotions light up.

When solving a difficult and personal moral dilemma, we really are of two minds. If the dilemma is not so personal, the reasoning part of the brain is dominant.

Of two minds

Researchers believed a particular region in the brain was involved in mediating conflict and was highly active in brains struggling with the crying baby scenario.

Greene and colleagues showed a neurological basis for the phrase \"of two minds,\" and that both compete for dominance. So does the heart rule the head? Answer: sometimes. But the head doesn't give in without a fight.

And we can use fMRI to go further.

\"Everything that evolves is a modified version of something else that already evolved,\" said Greene.

\"If you can trace the evolutionary history of the structures involved in a certain kind of thinking, then perhaps you can make the case that the thinking in question is shaped by the creature's evolutionary history.\"

This kind of thinking is what led Andreas Bartels, now at the Max Planck Institute for Biological Cybernetics in Germany, to propose that romantic love evolved from maternal love.

Similarly, Val Curtis of the London School of Hygiene and Tropical Medicine showed that our sense of disgust has evolved to protect us from disease.