Convergent validity involves examining whether a measure correlates well with other proxy measures for the same concept. Although measures of subjective well-being are focused on an inherently subjective concept, a range of information can be used as proxy measures for people’s subjective states. One option is to look at how ratings from the respondent compare to ratings from other people, such as friends, families, or even the interviewer. Similarly, one can observe the behaviour of the respondent to see whether it is consistent with their reported subjective state. Finally, one can use biophysical measures related to emotion states. All of these approaches have been applied to measures of subjective well-being and provide strong support for convergent validity.
Ratings of a person’s subjective well-being from friends and family have been shown to correlate well with self-reports of life satisfaction (Frey and Stutzer, 2002). A review by Pavot and Diener (1993) found correlations of between 0.43 and 0.66 between interviewer ratings and self-ratings, and correlations of between 0.28 and 0.58 between self-reports and other informants, such as friends and families. In a meta-analysis of self-informant ratings, Schneider and Schimmack (2009) found a mean correlation of 0.42 between self-reports of life satisfaction and informant reports. Similarly, for momentary affect, strangers shown a video or pictures of the respondent are able to accurately identify the subject’s dominant emotion at a particular point in time (Diener, Suh, Lucas and Smith, 1999). This latter finding also held when the informant was a person whose culture differed fundamentally from that of the respondent.
Subjective assessments of well-being are also reflected in behaviour. People who rate themselves as happy tend to smile more. This applies particularly to so-called “Duchenne” or “unfakeable” smiles, where the skin around the corners of the eye crinkles through a largely involuntary reflex (Frey and Stutzer, 2002; Diener, 2011). There is also good evidence that people act in ways that are consistent with what they say about their subjective well-being, i.e. people avoid behaviours that they associate with a low level of subjective well-being (Frijters, 2000). Diener (2011), summarising the research in this area, notes that life satisfaction predicts suicidal ideation (r = 0.44), and that low life satisfaction scores predicted suicide 20 years later in a large epidemiological sample from Finland (after controlling for other risk factors such as age, gender and substance use). Self-reports of job satisfaction have been shown to be a strong predictor of people quitting a job, even after controlling for wages, hours worked and other individual and job-specific factors (Clark, Georgellis and Sanfrey, 1998).
There have been a number of studies that look at the correlation between various bio-physical markers and subjective well-being. Measures of subjective well-being have been shown to be correlated with left/right brain activity (Urry et al., 2004; Steptoe, Wardle and Marmot, 2005). Activity in the left prefrontal cortex of the brain has been shown to be strongly correlated with processing approach and pleasure, while activity in the corresponding part of the right hand side of the brain is correlated with processing avoidance and aversive stimuli. Steptoe, Wardle and Marmot (2005) also investigated the association between the level of the stress hormone cortisol in the bloodstream and self-reported happiness, finding a 32% difference in cortisol levels between people in the highest and lowest quintiles of happiness. People reporting high levels of subjective well-being also recover more quickly from colds and minor injuries (Kahneman and Krueger, 2006).
There is no clear cut-off point for what constitutes an acceptable level of convergent validity. This is because the measured relationship depends as much on the quality of the proxy variable to which the measure is being compared as it does on the validity of the measure itself. However, the available evidence on convergent validity does allow for claims to be made about subjective well-being measures from the perspective of falsifiability. In particular, if it were found that a plausible proxy measure of subjective well-being showed no or a negative relationship with a measure of subjective well-being, this would be taken as good evidence that the measure in question lacked validity until the finding was over-turned, either because a good explanation for the relationship was found or because the result failed to be replicated. The consistent positive relationship found between measures of life satisfaction and the wide range of proxy measures considered above suggests strongly that such measures can be considered as displaying adequate convergent validity. The evidence for the convergent validity of affective measures is also persuasive. However, there is little to draw on with respect to convergent validity and eudaimonic measures.