Verified by 
I recently read a fascinating book about economics by Greek economist Yanis Varoufakis, called Talking to My Daughter About the Economy: or, How Capitalism Works—And How It Fails. Using engaging and accessible language and examples, Varoufakis describes the historical origins of the present economic system.
One section caught my eye—it was on how the concept of “interest” developed. Human beings have always carried debts—for example, telling their neighbor, “I owe you for the fish you caught.” However, with the invention of legal contracts, the debtor (the guy who ate the fish) is obligated to pay back the creditor (the neighbor who caught them). But contracts also came with a critical add-on—that is, the debtor generally had to pay back not only the original loan (of time or money) but something extra. That something extra—a surplus—is called “interest.”
Interest is one of the foundations of market economic systems. Without it, there would be no banks. And without banks, only the most rudimentary form of commerce would exist.
I got to thinking about the concept of interest and how critical interest is to make our market society run. But I am not an economist. My field is well-being science, and my lab studies how (and why) practicing activities like gratitude and kindness makes people happier.
The thing is—there is no “interest” placed on gratitude or kindness. If Brian expresses gratitude to Lucy, he would typically not expect her to reciprocate. But even if he did, he certainly would not expect her future gratitude to him to be even grander or more genuine or deeper than his own.
If Lucy does an act of kindness for Brian, she may or may not expect him to return the favor, but it would be odd for her to expect his future kind act to be even bigger or more effortful than hers.
The lack of interest on gratitude or kindness is one of the reasons that these practices are so powerful in creating positive emotions and making people more satisfied with their lives. Interest may be necessary in transactional relationships, but it is toxic when applied to our friends, neighbors, colleagues, family members, and sweethearts.
