This article is an excerpt from the bestselling book The Great Mental Models Volume 2: Physics, Chemistry and Biology
Reciprocity teaches us why win-win relationships are the way to go, why waiters leave candies with the bill, why it’s a good idea to use the least force possible to secure an outcome, and why a lot of companies don’t permit their employees to accept gifts. This model demonstrates why we should view giving as being as valuable as having. It prompts us rewrite the Golden Rule to say, “Do unto others knowing that something will be done unto you.” So what exactly is reciprocity?
In physics, reciprocity is Newton’s third law, which states that for every force exerted by object A on object B, there is an equal but opposite force exerted by object B on object A. Every force involves the interaction of two objects where the force asserted by one is reciprocated with an equally powerful and directionally opposite force by the other object. Forces always occur in pairs of the same type of force, and it is not possible for one object to exert a force without experiencing a reciprocal force.
When I land on the ground after jumping, I am exerting a force on the ground. At the moment of landing, the ground is also applying a force that is equal but opposite in direction on me. The earth applies a force on me even when I am just standing. This force is gravity. But the gravitational force exerted on me by Earth is reciprocated by me through the force I am exerting on the earth.
In the natural world, this third law of Newton’s explains jet propulsion. The word propulsion comes from two Latin terms meaning “forward” and “drive”—propulsion is a force that drives an object forward.1 Jet propulsion works by forcing matter, such as gas produced by burning fuel, in one direction, leading to a corresponding movement of the vehicle in the opposite direction. This holds true for everything from fireworks and guns to huge spacecraft.
Jet propulsion only works if the forward push is stronger than the forces acting on the object, like air friction and its own weight. The greater the force in comparison to drag (the amount of force opposing the motion), the faster the object can move. Octopi and squid force water through their mantle and out through a siphon at a high speed that compensates for their weight and the viscosity of the water. As the animal asserts a force on the water, the water exerts a force on the animal, and this makes the octopus or squid move.
Consider the tackle in American football. The force that the defender puts on the receiver’s body in order to bring him to the ground is equivalent to the force felt by the defenseman’s body during the tackle. You can’t initiate force without having a force put on you. For the tackle, this is very important. If the defenseman felt nothing there would be no incentive for him to be strategic in the application of his force on the receiver. And who would actually want to be a receiver if this were the case? If the guy who initiates the force feels nothing—much better to be him.
Since this is not the case, the tackle is more about using the least amount of force required to bring the receiver to the ground. It’s better for the receiver, and it’s also better for the guy doing the tackling, because the more force you apply to others, the more damage you do to yourself. Reciprocity can be summed up like this: when you act on things, they act on you.
What we give
It would be amazing if every time you did something good for the world, you received a corresponding amount of positive effect in your life. We all know that unfortunately this is not true. Sometimes positive intentions produce negative results, or bad things happen to people who do good things for others. Although the connection between good deeds and a good life isn’t perfect, there is a documented relationship between the two. Using the model of reciprocity can help us understand why people benefit themselves when they work for what they believe is good. The life of Norman Bethune,* a Canadian surgeon, is one that can teach us a lot about the nuances of reciprocity.
Bethune was not a volunteer in the sense we often use the term now to describe activities that are an adjunct to daily life. His efforts to help others were completely integrated into his work and life. What made him a volunteer is that he did it of his own volition, at no obvious personal benefit. Therefore, his story provides an interesting example to really explore reciprocity. What do you get when you give? What kind of tensions are created when the two forces interact?
Norman Bethune grew up wanting to be a surgeon, inspired by his doctor grandfather. He completed his studies during the First World War, during which he also volunteered providing medical support on the battlefield. During the 1920s he practiced medicine in the United States and Canada, eventually settling in Montreal. He initially specialized in thoracic surgery and developed a solid reputation as a surgeon. However, he had an ongoing commitment to help people beyond what he did in his practice. This goal he pursued in a variety of ways.
During the early 1930s, while in Montreal, Bethune provided medical services free to the poor and established a free-of-charge clinic he ran once per week. He vocally advocated for universal health protection, explaining that many medical issues were created by poverty and negligent employers. In addition, and unique for the time, he used radio broadcasts to educate the public on tuberculosis. Bethune volunteered his time, energy, and intelligence to try to bring about meaningful improvements in the lives of the most impoverished.
During the 1930s he became a supporter of communism and joined the Communist Party, mostly on account of what he saw of the benefits of the Soviet socialized health care system. These political beliefs took him further afield in his efforts to improve access to and outcomes in healthcare.
In 1936 in Spain during the Spanish Civil War, Bethune designed and developed the first ever mobile blood transfusion unit. This vehicle could draw and store blood, was used to give transfusions, and most importantly, could be used on the front lines of the battlefield. It was a remarkable innovation that saved countless lives and inspired the medical approach used in World War II.
All of the work that Bethune did in Spain, and later China, was not for profit. The mobile blood unit and all his other surgical innovations and inventions did not make Bethune any money.
In 1938 Bethune went to China, desiring again to help people. China was fighting a war with the Japanese, the Sino-Japanese War, and Bethune’s belief in communism led him to deploy his efforts in support of Mao and the Communist Party of China. He was made commander of all Chinese medical forces and immediately set about modernizing the existing primitive health care in China.
Helping the Chinese in their fight, he again deployed his practice of bringing the surgeon to the battlefield, designing mobile operating equipment and improving the survival rate of the injured. He also extensively trained doctors and nurses and established hospitals in areas that had neither. In their article, “The Medical Life of Norman Bethune,” Deslauriers and Goulet write, “His courage, determination and will to fully employ his talents of ingenuity, aggressiveness and selfless response to social concerns when the time came is truly remarkable.” He accomplished so much in his 18 months in China that when he died of septicemia after operating on a soldier, Mao delivered his eulogy, describing him as “a man who is of value to the people.”
Bethune’s achievements continue to be regarded as heroic by the Chinese. The first hospital he founded still exists, and his story is mandatory learning for primary school students in China.
Bethune’s story, however, is not solely one of accolades and recognition, heaps of positive effects achieved as a result of a life spent trying to bring about good. He died at age 49 as a direct result of his efforts to improve health outcomes on the battlefield. The fact that he was a communist led him to be written out of Canadian history during the Cold War years, when communism was seen as a direct threat to Western democracy. His personal life wasn’t great, and his aggressive personality earned him enmity from many colleagues.
Normally one would talk about a life like Norman Bethune’s in terms of sacrifice. He sacrificed personal relationships, social acceptance, and ultimately his life in order to take actions in accord with his beliefs and values. But using the lens of reciprocity suggests there is another way to interpret the story.
In a paper on the health benefits of volunteering in adults, the authors explain, “The beneficial effects of volunteering on health outcomes have been well documented. Research has found that participation in voluntary services is significantly predictive of better mental and physical health, life satisfaction, self-esteem, happiness, lower depressive symptoms, psychological distress, and mortality and functional inability.”6 Multiple studies have demonstrated the positive consequences of volunteering that are conferred on the volunteer. We may volunteer for a variety of reasons, based on our interests, goals or values, but regardless, we reap health benefits when we do so.
The studies on the positive aspects of volunteering for the volunteer bring to mind the concepts we outlined above in the science of reciprocity, like how forces always occur in pairs. Although volunteering is not governed by the laws of physics, using reciprocity as a metaphor can help us understand why volunteering appeals to so many people. And consequently, why some people make the choice to help others at seemingly great cost to themselves.
The research on volunteering makes it clear that when we give, we get. We improve our physical health; we feel better about ourselves and our place in the world. We evaluate our lives as having more meaning. One way of understanding people who take the kinds of actions that Bethune did, which on their face seem to risk so much, is that they receive a benefit from the world proportional to what they put out there. It’s not a benefit that can always be measured in legacy or reward. Sometimes those things come; for Bethune, although North America struggled for decades to appreciate him as the dedicated medical innovator he was on account of his political views, China continues to go all out in its appreciation of his contributions to their country.
However, perhaps the benefit is better conceptualized as the reciprocity received by the individual in terms of the satisfaction they have regarding the choices they’ve made. The act of doing good causes an equal reaction in terms of feeling good. In reading Bethune’s story it is clear that he was not motivated by recognition, but rather a genuine desire to help people that gave him an exceptional amount of energy and drive. It is highly possible that he didn’t evaluate his life as one of sacrifice, but instead derived satisfaction from his efforts. (See tit-for-tat.)
The rise of the “win-win”
In the physical world, the law of reciprocity works 100% of the time. The harder you punch a wall, the more force pushes against your fist, the more damage is caused to both you and the wall. In the biological world, reciprocity doesn’t have the same perfect record. However, it has been discovered to work much more often than not, and thus harnessing it has significant long-term benefits.
Evolutionary biologists argue that our tendency to engage in reciprocal behavior is a natural product of evolution. You are more likely to survive if you receive help from others. And you are more likely to receive that help if you have offered assistance in the past. So the genes that encode the reciprocal instinct were more likely to be passed on. And thus the fact that the human species has made it to now is directly dependent on our building social interactions that are reliable, useful, and trustworthy.
Humans engage in two types of reciprocity with each other: direct, which is “I help you and you help me;” and indirect, which is either a pay-it-forward concept, “I help you and then you help someone else,” or more about reputation building—“I help you, building a reputation as one who helps, so that someone else helps me in the future.” Both kinds work.
While reciprocity isn’t as reliable when it comes to humans as it is with physics, the concept can help you achieve better outcomes. Sometimes we go first and go positive and get nothing back, as is the case if we smile at a stranger walking on the street. Most times they’ll smile back at you, but every once in a while, you’re met with a scowl. We tend to forget the times our smile elicited a smile in response and remember the times when we received nothing in return, and so we stop smiling. However, the small loss we occasionally experience as a result of putting ourselves out there and not having it reciprocated is more than compensated for by the gains the rest of the time. If you want to get an idea of the true value of engaging in positive reciprocal behavior, just make a list of your outcomes in any given week. Life is easier and more enjoyable when we act on starting and maintaining win-win relationships with everyone. And as we explained, reciprocity has been part of our biological makeup for a very long time.
Let’s go back to the eastern Mediterranean around 1250 BCE. The bulk of the power in the region was held by the four kings of Egypt, Hatti (a region in present day Turkey), Assyria and Babylon. They didn’t like each other much—in fact, “they deeply distrusted each other and frequently squabbled.” Demonstrating military prowess was often a way that a king achieved legitimacy in the eyes of his subjects, and there were constant conflicts, from skirmishes to full-on battles between these four areas. Fighting was the norm.
Then, one day, as Trevor Bryce chronicles in his article on “The Eternal Treaty”, 15 years after a “great military showdown” between the Egyptians and the Hittites, an interesting thing happened. The two kings decided to enter into the world’s first known peace treaty.
The treaty was not about peace in the global sense, stemming from a desire to have a world without war. It was about peace in the immediate sense; two parties trying to establish a mutually beneficial relationship. The treaty, known as the Eternal Treaty, was the laying out of a directly reciprocal relationship between two civilizations.
Egypt was led by Ramesses, whose primary goal was to build “monumental construction projects, and to build his kingdom’s wealth through trade and the exploitation of its mineral-rich regions.”10 He had other security issues, most notably the Libyans to the west. So his interest in the treaty was to give himself some space to accomplish the legacy that mattered to him. The reality is, if you’re fighting with everyone all of the time you have to spread your resources along many fronts and you likely don’t have time to do anything else. One less border to defend was an opportunity to put his efforts elsewhere.
The Hittites had a similar problem, in a growing military threat from the Assyrians. In addition, their ruler Hattusili had usurped the throne from his nephew and was badly in need of some external power to legitimize his rule. Ramesses commanded great respect in the region, and his acknowledgment of Hattusili’s leadership would go a long way to maintaining stability. In pursuing the treaty with Egypt, “his hope was that Ramesses’ endorsement of his own position, and by implication that of his lineal descendants, would provide some security against future challenges.”
The treaty contained provisions for future military support, the kind of alliance in which an attack on one is an attack on the other. Assyria, despite having both interest and a good position did not, in fact, invade Hatti during Hattusili’s reign, so “quite possibly, the Egyptian-Hittite alliance did prove an effective deterrent against such an enterprise.”
Reciprocity based on self-interest is still reciprocity. Engaging in positive behavior to then be a receiver of positive behavior is about the long game. For both Ramesses and Hattusili, the benefits of trying to develop an alliance were clear. It gave them both an opportunity to exit fighting that consumed resources and allowed them to focus those resources on long-term stability and their legacies. Over time, the likelihood of reciprocal interactions increases, and thus it’s a much better strategy to try to make them positive. The more people you help, the more people you will have willing to help you.