Hedonic Treadmill - Major Empirical Findings

Major Empirical Findings

Lykken & Tellegen (1996) performed a 10-year, longitudinal, twin study and found that genetic factors have a significant impact on overall level of happiness, specifically that genetic factors may account for at least 44-52% of one's subjective well-being. They did so by administering subjective well-being questionnaires to a sample of 1,155 sets of identical and fraternal twins at the onset of the study, and then again 10 years later. After controlling for socioeconomic level, educational attainment, income, marital status, and religious commitment, they found a correlation of 0.44 - 0.52. This is a significant relationship, considering that fraternal twins' scores showed a correlation of less than 0.1. The researchers also found that the controlled demographic variables accounted for no more than 3% of the variance.Essentially, Lykken and Tellegen concluded that the variance in happiness observed in the sets of twins means that each individual’s happiness is almost equally determined by genetic factors and the experiences unique to each individual.

Diener & Fujita (2005) studied the stability of one's level of subjective well-being over time and found that for most people, there is a stable range in which their level of satisfaction varies. To measure the stability of one's level of well-being, they asked a panel of 3,608 German residents to rate their current and overall satisfaction with life on a scale of 0-10, once a year for seventeen-years. However, about one quarter of participants exhibited shifts in their level of life satisfaction over the course of the study, and 9% of participants experienced significant changes. They found that level of life satisfaction is more stable in the long run than it is in the short run, and that those with a higher mean level of life satisfaction also had more stable levels of life satisfaction compared to those with lower levels of satisfaction, who experienced more fluctuation in their levels of satisfaction throughout the course of the study.

Headey (2008) concluded that an internal locus of control along with "positive" personality traits (notably low neuroticism) are the largest significant factors affecting one's subjective well-being (SWB). The author also found that adopting "non-zero sum" goals, that is those which enrich one's relationships with others and with society as a whole (family-oriented and altruistic goals), increase the level of SWB. Conversely, attaching importance to zero-sum life goals: career success, wealth, and social status, will have a small but nevertheless statistically significant negative impact on people's overall subjective well-being (even though the size of a household's disposable income does have a small, positive impact on SWB). Duration of one's education seems to have no direct bearing on life satisfaction. And contradicting set point theory, there is apparently no return to homeostasis after sustaining a disability or developing a chronic illness. These disabling events are permanent, and thus according to cognitive model of depression, may contribute to depressive thoughts and increase neuroticism (another factor found by Headey to diminish SWB). In fact disability appears to be the single most important factor affecting human subjective wellbeing. The impact of disability on SWB is almost twice as large as that of the second strongest factor affecting life satisfaction—the personality trait of neuroticism.

Although Headey (2008) concluded that there is apparently no return to a person’s overall happiness set point after sustaining a severe disability, a study conducted by Silver (1982) found contradicting results. For eight weeks, Silver followed accident victims who had sustained severe spinal cord injuries. About a week after their accident, Silver observed that the victims were experiencing much stronger negative emotions than positive ones. However, by the eighth and final week, the victims’ positive emotions actually outweighed their negative ones. The results of this study suggest that regardless of whether the life event is significantly negative or positive, people will generally always return to their happiness baseline.

Baumeister, Bratslavsky, Vohs, and Finkenauer (2001) performed a meta-analysis in which they looked at the impact of bad events in comparison to positive events in an individual’s life. They found that bad events had a greater impact psychologically on a person than positive events. A study carried out by Lucas, Clark, Georgellis, and Diener concurred with this finding. Although the study was focused on adaptation to changes in marital status, one of their largest findings was that widowhood has long lasting effects and not all widows experienced significant amounts of adaptation, while most married people did. While demonstrating that a negative life event can have a greater impact on a person’s psychological state and happiness set point than a positive event, this study also illustrated that the amount of adaptation that occurs is largely on an individual basis.