The purpose of these studies was to develop a valid measure of trait gratitude, and to evaluate the relationship of gratitude to subjective well-being (SWB). Four studies were conducted evaluating the reliability and validity of the Gratitude Resentment and Appreciation Test (GRAT), a measure of dispositional gratitude. This measure was shown to have good internal consistency and temporal stability. The GRAT was shown to relate positively to various measures of SWB. In two experiments, it was shown that grateful thinking improved mood, and results also supported the predictive validity of the GRAT. These studies support the theory that gratitude is an affective trait important to SWB.
Watkins, P. C., Woodward, K., Stone, T., & Kolts, R. L. (2003). Gratitude and happiness: Development of a measure of gratitude, and relationships with subjective well-being. Social Behavior and Personality: an international journal, 31(5), 431-451.