Scientists should conduct more differentiated surveys. For example, comparing "pre-defined" and "improvization" prayers; or comparing different denominations' prayers (non-denominational ones included); or comparing the praying yields - these would be interesting surveys. Prayer itself is also just one part of things called "sadhana" - other fields would be also interesting to investigate, beginning with getting up early in the dawn.

I would be curious, then, how they measure the happiness of life.