Is Love a Supercritical State of the Brain?

The Critical Brain Hypothesis and The Feeling of Love

by Ryan Ripsman

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            You’re walking alone in an unfamiliar part of town. It’s late at night, the lights are dim, and you have a nagging sense of unease. Suddenly, you hear a small crinkle from behind you. Instantly, your heart starts pounding, you tense up, and your legs feel ready to run. Even though you’ve only been exposed to a small noise, from an evolutionary perspective, it’s crucial your body has a fast, unified response. Scientists have shown that evolution has designed a brain that is quick and highly interconnected, but the mechanism by which the brain is able to achieve this remains elusive.

One popular explanation for the brain’s processing speed and interconnected nature is that the brain functions in a critical state. A system in a critical state is highly correlated, meaning the action of one component can directly affect a different, far-away component. In the brain, this would be akin to a neuron firing in one area like the auditory cortex causing the firing of nerves in a far-off area like the amygdala, the part of the brain responsible for our fear response. Critical systems are also complex, meaning they cannot be thought of as merely the sum of their components. This complexity may explain our difficulty in understanding the brain by looking at the firing of neurons in individual parts of the brain. A critical brain can only be understood by examining the firing of all its neurons.

            The idea of a critical brain isn’t just an interesting idea: there is some compelling evidence that it may describe the brain’s behaviour. A key feature critical systems exhibit is a power law distribution. In any given system, random disturbances are happening all the time. However, large random disturbances are much less frequent than small ones. The power law describes how the probability of a disturbance goes down as its size increases. In the case of the brain, the disturbances are called neuronal avalanches, which are random bursts of brain activity. Several studies have shown that the size of neuronal avalanches in slices of the brain grown in a lab follows a power law distribution which supports the critical brain hypothesis. However, since non-critical systems can also exhibit the power law distribution, more rigorous research needs to be conducted to confirm that the brain exists in a critical state.

            One defining feature of criticality is that it exists as the midpoint between two different states, the subcritical state and the supercritical state. When a system crosses over from the subcritical to the supercritical state, it is said to be undergoing a phase transition. The clearest example of this phenomenon is melting ice. When ice is heated it undergoes a phase transition from a solid, the subcritical state, to a liquid, the supercritical state. When ice is on the verge of melting, it is in a critical state.

            The critical brain hypothesis has important implications for our understanding of neurological illnesses. It has been suggested that during seizures, the brains of people with epilepsy may transition to a non-critical state. If this is true, it may allow clinicians to detect seizures earlier, so that anti-epileptic medication can be taken before the seizure starts. Similarly, it has been suggested that Parkinson’s disease may also involve a transition of the brain to a supercritical state.

            One intriguing idea recently suggested in a paper by two scientists from Clermont Auvergne University is that falling in love is a phase transition to a supercritical state. This hypothesis would explain some of the classical features of falling in love. For instance, people in love traditionally overlook the flaws in their partners. The authors suggest that the lack of recognition of their partner’s flaws could be because when people are in love, their brain is in a supercritical state which is less efficient at information processing than the normal, critical state of the brain.

To show that love is a phase transition, the scientists analyze a selection of quotations from literary sources and private diaries to show that the characteristics of falling in love resemble the characteristics of a phase transition. If love is a phase transition, it should at first come on very fast, before plateauing. The scientists had a group of volunteers rate quotations from famous romance literature including Romeo and Juliet and Lily of the Valley based on the intensity of the love exhibited in the quote. As would be expected in a phase transition, the intensity of the love increased extremely fast before plateauing in each of the novels. The study is very speculative, but it introduces an interesting hypothesis: that falling in love shares some characteristics of a phase transition.

            While it may not seem important that love may be a supercritical state, this research is intriguing for a couple of reasons. First, it is an excellent example of multidisciplinary research. Very few research studies use biological, physical, psychological, and literary criticism techniques altogether. However, as we begin to probe the most fundamental questions about ourselves and our universe, research methods that transcend arbitrary scientific boundaries will become more important. But, even more important than the methodology, this study’s results raise intriguing philosophical questions. If something like love, which is intrinsic to the human condition, can be explained by the firing of neurons, what separates us from machines?  If love is just a physical change of state, does that change its value?

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