Can I test whether or not a correlation (between ES and PSM, below) is spurious directly?

I thought I might ask people to evaluate fictional others but the existence of a fictional correlation does not prove that a self-evaluatory correlation is fictional. Does anyone have any better suggestions?

Background

I have a student who wants to investigate the connection between positive psychology and public service, with a view to showing that they are correlated, and suggesting that positive psychology may be causal in promoting better public service. I am aware that correlation does not prove cause but more fundamentally, it seems to me that, as in the case of much research in the positive psychology field, even the correlation may be spurious due to self-evaluation style.

After all Martin Seligman's positive psychology scale, the Explanatory Style (ES) scale is just that - a measure of how people explain things. If it turns out to be the case that positive psychology as measured by the ES should correlate with e.g. Perry (1996)'s Public Service Motivation (PSM) scale, as I think is very likely, then it would only seem to prove to me that people that explain themselves positively explain their public service motivations positively as well.

The reality may possibly be quite the reverse.

I thought first of all like to attempt to obtain objective data on service, by obtaining evaluation by others, or by having subjects respond to some sort of test (e.g. asking for and obtaining help) but I am not sure whether the former will be available, or whether the latter will be a good indicator of service in the real world.

Another possibility would be to compare not individuals but groups. E.g. The correlates of self esteem at an individual level are very positive, but may be far less so at a national level. This data may be hard to obtain.

Seligman, M. E. P. (1995). Learned optimism. New York, Knopf.

https://web.stanford.edu/class/msande271/onlinetools/LearnedOpt.html

Perry (1996)

https://www.researchgate.net/publication/31448729_Measuring_Public_Service_Motivation_An_Assessment_of_Construct_Reliability_and_Validity