Big Brains: Why Death, Divorce, and Breakups Are So Painful


My dad died more than 10 years ago. I still remember the day. I was calling home and no one was picking up. My aunt told me my family was at the funeral. We bury our dead within a period 24 hours.

It was the first time I encountered death. Far from home and alone, I felt lonely and I did not know what to do. I remember waking up the next day, realizing I would never see my dad again and crying. I forgot when I had last cried.

Death of loved ones, divorces, and breakups are the most traumatizing events in our lives. The events are profound and painful. These experiences are visceral; we feel them at a deep, biological level.

They have one thing in common: termination of close social connections. We have a strong aversion to social isolation and loneliness.

Why is our reaction to social separation so dramatic?

Big Brains

In general, the brain size is a function of body weight. That’s why whales have bigger brains than mice. The body mass to brain size relationship is called encephalization.

There is a formula. You drop body weight, it spits out expected brain size. The formula works well for some animals, but for others it produces smaller (than observed) brain sizes. The encephalization quotient is used to measure this deviation.

Animals with higher quotient numbers have more spare/underutilized intelligence capacity. They tend to be smarter. The animal with the highest quotient number? Human.

encephilization                                                                                                                                                   Source: Wikipedia

Dunbar number

Robin Dunbar had an idea.Dunbar is an anthropologist.

He noticed a correlation between brain (neocortex) size and a group size in primates. He observed that the more intelligent the primate, the bigger the social group size.The large group provides a clear survival advantage. It is easier to hunt for prey and defend against predators. The downside? Competition for food and mating partners.

So, to succeed within the group setting, primates had to learn various social strategies. For many primates, it’s mutual grooming. For humans, it’s making friends, forming alliances, and punishing enemies.

Strategizing is hard. The larger the group, the higher the number of possible relationships between members. If the group has 5 members, there are 10 potential dual relationships in the group. For a group size of 150, there are 10,000 potential relationship pairs. Keeping track of all these relationships requires significant mental capacity.

The bigger the social group, the more mental power needed for animals living in that group. This where the underutilized intelligence (as measured by encephalization quotient) came handy.

Dunbar showed that human brain maxes out at the group capacity of about 150. One hundred eight to be precise with 95% interval of 100 to 230. This is a Dunbar number.

It shows up again and again, from farming village sizes to social networks. Malcom Gladwell mentioned the number in his book “The Tipping Point“.


Disadvantages of Big Brain

While having a big brain provides big evolutionary benefits to humans, there are costs.

The human brain is only 2% of our body and yet it consumes 20% of its energy. The number is even higher for children. The large skull in human also complicates labor, making childbirth dangerous.

The large brain needs to grow and the process takes forever. So, the brain has to develop outside of the mother’s body. That makes human (or in general, mammalian) infants completely dependent on a caregiver.

To ensure the parent does not abandon the child, evolution had to develop a connection between caregiver and an infant. In mammals, this connection takes shape in social attachment. Evolution co-opted pain to enforce it.

Social Pain = Physical Pain

When we describe emotional pain we use the same words we do for physical pain (heart broken, crushed, wounded, etc.). Does this mean the brain uses the same neural system to process social pain?

The short answer is yes.

There are cries that mammal infants make when separated from caregivers (1). The sounds are called distress vocalization cues. Researchers found that majority of infants make them upon separation. The infants depend on their caregiver, so the split threatens their lives and is emotionally painful.

If social and physical pain share the same neural infrastructure, then painkillers that alleviate physical pain should also relieve social pain.

Jaak Panksepp tested this theory. He isolated guinea pigs pups, waited for the distress vocalization cues, and administered low doses of morphine. Morphine eliminated the distress cues. This experiment was replicated across other mammals as well, with similar results.

The bodies make their own version of morphine called opioids. Just like the morphine, opioids are addictive. A reunion between the mother and infant increases opiate levels in both parties and prolactin increases opioid production in mothers.

Also, dissolution of relationship often feels like a withdrawal. Furthermore, people in romantic and/or socially supportive relationships have higher pain tolerance.

So the same chemical used to reduce physical pain is used for social pain. That was the first evidence that both sensations share neural circuitry.

Second evidence came from neuroimaging studies. The research on social pain in humans showed that the brain registers social pain in dorsal anterior cingulate cortex (dACC) and anterior insula (AI) regions of the brain.

brain V2

Not surprisingly, both regions register an emotional experience of physical pain as well. Furthermore, dACC and AI have some of the highest concentration of opioid receptors and opioids are used to reduce affective (emotional) of aspects of pain. These brain areas are absent in reptiles, who don’t take care of their offsprings.

From an evolutionary standpoint this overlap makes sense. Evolution rarely creates something from scratch, but rather, builds on existing foundations.

Broken Bones, Broken Hearts

However, the most profound implication becomes clear once you understand the purpose of pain.

Pain is a warning. It’s an indication that something is threatening our survival. Thus, our brain perceives separation of social ties as damaging as a physical injury. Broken hearts and broken bones are all the same to our brain (2).

Pain from a cut in your finger aims at keeping your limbs together. Pain from your dissolved social ties is aimed at keeping your social connections together.

And this is the story. To live in groups, we had to develop large brains. Yet, large brains take a long time to grow.

So, evolution created a connection between caregiver and child. It used pain (among other means) to enforce the social attachment. We carry this connection with us as we grow. Whenever close social ties break, we experience emotional pain that feels like physical pain.

In his book “Social: Why Our Brains Are Wired to Connect” (this post is based on the book), Matthew Lieberman explains that evolution struck a bargain with us.

Every time we connect with another human who can leave us or withhold the affection, we expose ourselves to the possibility of pain. Social pain that feels real. That’s the price we pay for having a big brain.

Unintended Consequences:

1. Perhaps the most curious implication is the factors that decrease physical pain also decrease social pain. Research showed that taking Tylenol reduced self-reported social pain. It also reduced activity of brain regions responsible for processing emotional aspect of the pain (dorsal anterior cingulate cortex (dACC) and anterior insula (AI)) after experimental episode of social exclusion.

2. Presence strong social network is shown to reduce social pain. Viewing a picture of loved one (as opposed to stranger) lead to a reduction in self-reported pain.

3. dACC and AI may play a role in translating loneliness into inflammatory activity, i.e. there’s evidence that social isolation can cause inflammation activity in the body. People who are lonely (or more likely to feel lonely) are at a greater risk of developing inflammatory-related diseases. This is a disturbing implications, especially for the developed countries where people work long hours in socially isolated environments.



Social: Why Our Brains Are Wired to Connect



  1.  Separation has very detrimental impact on mammals. It leads to increased production of stress hormone (cortisol) and impacts infant’s long-term cognitive development. Studies carefully document the impact of separation. Robert M. Sapolsky, mentioned number of studies in his book “Why Zebras Don’t Get Ulcers” that show how loss of a parent to death during childhood increases the lifelong risk of depression. For example, research from Romanian orphanages showed that the longer the child spent in the orphanage, the higher the resting glucocorticoid (stress hormone) levels are in their body.
  2. Pain has aspects that are processed differently, but our brain ties it into one experience. dACC and AI brain regions process emotional (affective) aspects of the pain.
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