Science of Gratitude

Reciprocal Altruism

Ever helped a friend move thinking someday when you move, they may repay the favor?
Or helped a co-worker with a project hoping they would help with your work?
Or donated to a charity and shared it on social media?
Or paid for a stranger’s coffee for the karma points?

Reciprocal altruism is when altruistic behaviors are performed because they increase the likelihood of repayment in the future (Trivers, 1971). Reciprocal altruism fits better with Darwinism because animals saw benefit to themselves through helping others.

Robert Trivers, who introduced the theory of ‘reciprocal altruism’ in 1971, suggested gratitude as one of the factors which regulates our response to altruistic acts by others (Trivers, 1971). Gratitude may have even developed as a mechanism to drive reciprocal altruism as a way of turning strangers into friends/allies (Smith, et al., 2020).

Morality is used normatively to refer to a code of conduct which, given specified conditions, would be put forward by all rational people (Gert & Gert, 2020). As society has evolved, gratitude has continued to be part of the moral code, but not because humans continually feel indebted to each other. Instead, gratitude has evolved due to the intention behind the reciprocity: empathy.

While there are caveats to comparing primates and humans, isn’t it interesting how gratitude and empathy may have been around since before our own species’ evolution?

Gratitude researcher and psychologist Michael McCullough suggested gratitude has 3 moral functions (McCullough, et al., 2001):

• Response to others’ moral actions.
• Motivator to behave morally/prosocially towards others.
• Reinforcer to behave morally in the future.

“Gratitude, as it were, is the moral memory of mankind. In this respect, it differs from faithfulness by being more practical and impulsive: although it may remain, of course, something purely internal, it may yet engender new actions. It is an ideal bridge which the soul comes across again and again, so to speak, and which, upon provocations too slight to throw a new bridge to the other person, it uses to come closer to him.” —German sociologist Georg Simmel (1858-1918)

As gratitude is felt in response to others’ actions, it motivates and reinforces the sociability and morality of others.  In this way it is a fundamental force of what allows society itself to evolve: by strengthening bonds between members of the same species who mutually help each other out.

For more on morality and empathy, check out the Values section of Discovery.

The Broaden and Build Theory

Gratitude is part of an upward spiral contributing to positive emotions and experiences, which in turn translate to improved well-being. In 2004, scientist Barbara Fredreickson theorized the Broaden and Build Theory of positive psychology. The theory suggested:

“By broadening an individual’s momentary thought–action repertoire—whether through play, exploration or similar activities—positive emotions promote discovery of novel and creative actions, ideas and social bonds, which in turn build that individual’s personal resources; ranging from physical and intellectual resources, to social and psychological resources. Importantly, these resources function as reserves that can be drawn on later to improve the odds of successful coping and survival (Fredrickson, 2005).”

In other words, positive emotions (love, gratitude, joy, etc…) broaden thoughts and actions which build personal experiences leading to enhanced health and fulfillment. When we are healthy and fulfilled, we feel more positive emotions which creates an upward spiral of positivity.

Gratitude Can Strengthen Our Relationships

Incorporating a practice and mindset of gratitude into your life helps to strengthen your relationships with family, friends, and significant others. We rely on gratitude to form reciprocal relationships with others.

Researcher and author Robert Emmons says:

“I see it as a relationship-strengthening emotion, because it requires us to see how we’ve been supported and affirmed by other people.”

Overall, gratitude has been associated with several relational and prosocial factors:

• Gratitude has been linked to activity in the oxytocin system, which contributes to our ability to appreciate positive feelings in relationships (Algoe 2014).
• Research has found when couples express gratitude for each other, they each become more satisfied within the relationship (Gordon, 2015).
• One Study found that participants’ reported feelings of gratitude towards a romantic partner predicted who would stay in their relationships and who would break up nine months later (Gordon, 2015).
• A lack of gratitude can impact dissatisfaction within partnerships in terms of the division of labor (Trethewey & Alberts 2007).
• Gratitude encourages forgiveness (see video below)
• Gratitude supports the process of making new friends. An Australian study found recipients of expressions of gratitude were more likely to extend the effort to start a new relationship with the novel peer (Williams & Bartlett, 2015).
• Gratitude encourages empathy and sensitivity and decreases aggression towards peers (Ziegler, 2011).

Friendships and strong social circles carry their own list of benefits like a longer lifespan, less stress, and quicker recovery after disease. This is explored more in the Friendship section of this site.

Gratitude Helps the Community

“Gratitude makes society habitable.”  — Georg Simmel

Not only does gratitude benefit one’s own health, relationships, and happiness, but gratitude can have a trickle-down effect on those around us and the greater community.
Prosocial behavior often calls us to pay it forward. 

Gratitude can lead to altruism and philanthropy because of the neural link between the behaviors (Smith, et al., 2020). When we feel grateful for what we have, we have a yearning to give back either to those less fortunate or return the favor to those who helped us.

For essential workers like health care providers and teachers, gratitude has been researched as an intervention to lower burnout levels:

A 2010 study of 96 teachers in Hong Kong indicated: “the dispositional gratitude of teachers correlated substantially and positively with a meaningful life orientation to happiness and with personal accomplishment, and correlated substantially and negatively with the two negative components of burnout: emotional exhaustion and depersonalization (Chan, 2010).”

A 2015 study of 102 health care practitioners found: “relative to control, the gratitude group reported lower depressive symptoms (−1.50 points; 95% CI [−2.98, −0.01]; d = −0.49) and perceived stress (−2.65 points; 95% CI [−4.00, −1.30]; d = −0.95) at follow-up.” The study concluded: “Taking stock of thankful events is an effective approach to reduce stress and depressive symptoms among health care practitioners (Cheng et al., 2015).”

Gratitude supports our physical and mental health.

As gratitude and its effects have come to the forefront of people’s minds, research has come out testing the effects of practicing gratitude on the brain, and whether it has any long-lasting effects on overall mental and physical health.

Mental Health

Gratitude is being explored as an intervention method in positive psychology therapy practices (Wood, et al. 2010).

As this Meta Analysis highlights, gratitude interventions hold a strong place in the practice of positive psychopathy. A few interesting points regarding mental health from the review (Wood, et al. 2010):

• Thankfulness predicted significantly lower risk of major depression, generalized anxiety disorder, phobia, nicotine dependence, alcohol dependence, and drug “abuse” or dependence (odds ratios = .81 to .84).
• Thankfulness was related to a much lower risk of Bulimia Nervosa (odds ratio= .60)
• In a study of participants with impaired body satisfaction, 76% of participants completing the intervention would be less body dissatisfied than a matched control group.
• In a study of participants with “excessive worrying” or anxiety, the gratitude condition led to a significant and large decrease in worry (1.5 standard deviations).

Like most mental health interventions, gratitude can be a helpful tool for some people, and may not be effective for others.

Gratitude has also been shown to increase resilience and improve recovery time after trauma.

• A 2006 study examined Vietnam War veterans with and without PTSD. The study found: Vietnam War Veterans with higher levels of gratitude experienced lower rates of Post-Traumatic Stress Disorder. Practicing daily gratitude accounted for a significant incremental proportion of the variance in daily rewarding social activity (B=.12, SE = .05, t(26) = 2.30, p = .03, d = .90), intrinsically motivating activity (B = .11, SE = .05, t(26) = 2.19, p = .04, d = .86), and greater daily self-esteem, (B=.25 SE=.06, t(26)=3.94, d=1.58), than those without a disposition of gratitude (Kashdan, et al. 2006).
• A study of women with metastatic breast cancer showed: women who practiced gratitude for others experienced up to 50% more social support than those who did not even 3 months after the end of the study (Algoe & Stanton, 2012).
• Two studies sponsored by the Greater Good Science Center surveyed victims of traumatic events (a bombing in Israel and an earthquake in Indonesia). Both studies found in the immediate aftermath of the event, gratitude had little effect, however after time, gratitude seemed to speed up overcoming the psychological damage inflicted by disaster. “Both studies suggest the answer may lie in gratitude’s ability to make us take a second look at our lives, turning our attention from the bad things to the good—a cognitive process that needs time to unfold (Smith, 2014).”
• A 2003 study studied resilience following the terrorist attacks on September 11. Positive emotions such as gratitude and love contributed to resilience and growth in the wake of the attacks (Fredrickson, et al., 2003).

Gratitude seems to act as a buffer against depression and fuels growth in the time following traumatic events.

The way in which gratitude allows us to focus on the good parts of life, rather than fixating on the bad parts helps boost confidence and self esteem.

• Research has shown those who practice daily gratitude report an overall greater amount of self-esteem (B=.25 SE=.06, t(26)=3.94, d=1.58), than the control group (Kashdan, et al. 2006).
• Another study of collegiate athletes found athletes with higher levels of gratitude increased their self-esteem over time and reduced levels of social comparison, both of which contributed to better performance (Gratitude atTime 1 had a positive correlation with self-esteem at Time 1 (r=.39, p<.01) and Time 2(r=.20, p<.01), respectively) (Chen & Wu, 2014).

Physical Health

First and foremost, because of the broaden and build theory, positive emotions and improved mental health have a huge effect on physical health.

In other words, gratitude does seem to have an effect on social well-being, and while gratitude may have an effect on physical health, there are no specific boosts to physical health via gratitude that are not available from another source.

While practicing gratitude is not the only specific way to reap physical health benefits, research shows it definitely doesn’t hurt.

In studies, participants who practiced gratitude…

• Experienced up to 50% more social support than those who did not — even 3 months after the end of the study (Algoe & Stanton, 2012). (See the Friendship Section on more research into social support and health)
• Had lower levels of depression — The results of a meta analysis showed a significant association between gratitude and depression, r = -0.39 (95% confidence intervals -0.44, -0.34) (Iodice et al., 2021).
• Exercised 1.5 hours a week more on average compared to the control group (Emmons & McCullough, 2003).
• Experienced improved sleep (−0.26, CI (−0.46 to −0.05), p = 0.014) (Jackowska, et al., 2016).

Gratitude Contributes to Our Happiness

‘Happiness’ isn’t simple. (You can learn all about the subjectivity of happiness, and the 4 Elements of Well-Being in the ‘Happiness’ section)

However, focusing on the good things in life can increase levels of joy and promote overall well-being (Emmons & McCullough, 2003), which fosters feelings of happiness.

In one study, participants  showed up to a 10% decrease in detrimental emotions like envy, resentment, frustration, aggression, and regret after practicing gratitude (Emmons & McCullough, 2003).

Negative Bias: The human brain is wired to focus on the negative. Gratitude helps the brain refocus on the positive or find silver linings.

Author and gratitude scientist Robert Emmons conducted an experiment in 2003 to measure happiness via gratitude called Counting Blessings and Burdens. He used 300 participants split into three groups. Each week for 10 weeks, the groups wrote in a journal. Group A wrote 5 things they were grateful for in the past week, Group B described 5 hassles from the past week, and Group C (the control group) wrote 5 things that happened or affected them in the last week.

At the end of the 10 weeks, Emmons found the participants in Group A ranked 25% happier on the study’s scale than the participants in the other groups (Emmons & McCullough, 2003).

The Hedonic Treadmill

The Hedonic Treadmill, also known as Hedonic Adaptation, is the observed tendency of humans to quickly return to a relatively stable level of happiness despite major positive or negative events or life changes (Rosenbloom 2010). Hedonic adaptation says eventually, your state of being will be your norm and you will become dissatisfied with the norm and want more.

Gratitude is an effective antidote to falling into the hedonic cycle. When we focus on the good things we have, we are less likely to be dissatisfied and more likely to be happy with what we have. Gratitude helps us get off the hedonic cycle and reset.

“For my part, I am almost contented just now, and very thankful. Gratitude is a divine emotion: it fills the heart, but not to bursting; it warms it, but not to fever.” — Charlotte Brontë

Videos Explaining Gratitude and Happiness Experiments

Seeing Happiness and Gratitude in Action