The Brain on Gratitude
With Thanksgiving just around the corner, now is as good a time as any to stop and think about the concept of “gratitude.” The general consensus seems to be that gratitude is good for you, being consistently correlated with better physical, psychological, and social health. But for all its supposed benefits, there is still plenty that we don’t fully understand about gratitude.
How do you even define “gratitude”? Is it a personality trait or an emotion or simply good manners?
Psychologists in this field define gratitude as a two-step process: 1) “recognizing that one has obtained a positive outcome” and 2) “recognizing that there is an external source for this positive outcome” . Beyond this, gratitude may be classified: as a trait, or someone’s innate ability to be grateful, and as a state, a fluctuating feeling of gratitude over time.
So how are scientists working to fundamentally understand gratitude, its biological basis, evolutionary purpose, etc.? For those of us who work with mice or worms, this does not sound like a simple task. Lucky for us, the field of gratitude research (currently led largely by social psychologists) has seen a recent spike in interest, and there are concerted efforts to expand our understanding of this topic.
Survival of the Most Grateful
Although we usually think of gratitude as a social construct, it may actually have deep roots in evolutionary history. Scientists theorize that gratitude may have evolved as a mechanism to reinforce altruism. A wide variety of animals engage in “reciprocal altruism, behaviors that one animal performs to help another member of their species, even [when that may come] at a cost to themselves…” . Studies with chimpanzees, for instance, show that a chimp who has received help with grooming or retrieving food is more likely to return the favor to its helping partner . Altruism is essential to the survival of many species, and yet, its evolution is a paradox that troubled even Darwin.
It’s easy to see how altruism could arise between family members (if my kin survive, so does my particular pool of genes: biological success!), but it’s harder to imagine how such altruistic behavior could arise between nonkin individuals. Researchers propose that gratitude may have “evolved to help convert acquaintanceships with nonkin into relationships that can support reciprocal altruism”. By this logic, we may think of gratitude as a social “glue” that brings non-family members together into a community. This is supported by the fact that one is more likely to feel gratitude toward acts of kindness from strangers than from family members .
The Brain on Gratitude
Although the idea of studying gratitude has been around since the time of ancient philosophers, methods for its rigorous study at the biological level have been limited. With the advent of fMRI to study brain activity during numerous types of tasks, scientists have recently been able to identify key brain regions that are differentially activated by the experience of gratitude. Research participants may be presented with written scenario descriptions involving friends [7, 8] or in one case, to imagine that they were Holocaust survivors who had received life-saving assistance from complete strangers . Some of the brain regions implicated by these studies include:
- mesolimbic and basal forebrain (associated with feelings of reward and the formation of social bonds) 
- inferior temporal cortex (associated with interpreting other people’s intentions) 
- medial prefrontal cortex (PFC) and anterior cingulate cortex (ACC) (associated with moral cognition, perspective-taking, and reward) 
It isn’t surprising that something as complex as gratitude would activate multiple brain regions. It can feel good to give thanks to someone, especially if we are particularly moved by considering someone’s intentions or perspective of us.
You Can Thank Your Parents
Furthermore, some genes have been identified that may be linked with “trait” gratitude. One variation in the CD38 gene, which is involved in the secretion of oxytocin, was linked with “the quality and frequency of expressions of gratitude toward a romantic partner in both a laboratory setting and in daily life” . In another study, a particular variant of the COMT gene, which is involved in dopamine recycling, was linked with greater trait or “dispositional” gratitude, even after controlling for non-genetic factors like socioeconomic status and religion . Both of these studies implicate neurotransmitters popularly associated with “love” and “happiness”.
A Dark Side to Gratitude?
We may not fully understand the nuts and bolts of it yet, but we can all agree that gratitude is a good thing, right? Mostly. Although most research seems to support this idea, studies also indicate that gratitude can have a dark side to it. Individuals with disabilities sometimes feel “burdened” by their need to thank their caregivers and frustrated with the one-sidedness of the relationship . Moreover, a 2016 study linked higher trait gratitude with greater efforts to maintain an abusive relationship . As researchers explore these topics, it will also be necessary to take into account cultural and developmental differences that influence how people experience and express gratitude.
Still, active efforts to put gratitude into practice, (like, for example, through gratitude journaling), have been shown to improve sleep , reduce biomarkers of inflammation in heart failure patients , and improve symptoms of mental health , among other benefits. UC Davis psychology professor Robert Emmons encourages people to get creative when it comes to gratitude, writing, “Mother Theresa talked about how grateful she was to the people she was helping, the sick and dying in the slums of Calcutta, because they enabled her to grow and deepen her spirituality. That’s a very different way of thinking about gratitude—gratitude for what we can give as opposed to what we receive. But that can be a very powerful way, I think, of cultivating a sense of gratitude” .
- Allen, Summer (2018) The Science of Gratitude. Greater Good Science Center. White paper.
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