The expressions of gratitude are based on social reciprocity in everyday life and understandings of rights and duties surrounding mutual assistance and collaboration. There is cross-cultural variation to this. Universal tendencies of social reciprocity does not equate to practices of expressing gratitude.

Social reciprocity is a basic element of human organization that involves the mutual exchange of goods, services and support among individuals, allowing individuals to achieve more together. People can expect others to assist them in the achievement of individual goals as well as to collaborate in the achievement of common goals. They can anticipate that others will assist and collaborate in return. This reflects principles of cooperation that have been argued to be at the center of human evolution, including the development of human communication.

If gratitude’s role in the maintenance of social reciprocity in different societies is evidenced by its verbalization (e.g. ‘thank you’), we would expect this to occur frequently in episodes of informal everyday interaction where someone seeks and obtains a good, service or support from another. What has been found instead is that expressions of gratitude in these episodes are remarkably rare, suggesting that social reciprocity relies to a large extent on tacit understandings of people’s rights and duties surrounding mutual assistance and collaboration. At the same time, it has also been found that minor cross-cultural variation, with slightly higher rates in Western European languages, including English, showing that the potentially universal experience of gratitude should not be conflated with culturally variable practices of expressing gratitude. The idea that gratitude’s role in social reciprocity is tied to saying ‘thank you’ appears to be largely based not on systematic empirical observation but on attitudes about politeness in English-speaking society.

Universals and cultural diversity in the expression of gratitude (royalsocietypublishing.org)