You know the surveys being taken where nations are asked to rate their happiness as a country?Turns out there's a scientific reason why some places rate themselves higher than others.  Science Daily reports that the citizens of countries that rate themselves happiest all have a specific genetic feature in common. Apparently, their DNA is more likely to contain a specific allele involved in pain reduction and sensory pleasure. Michael Minkov of the Varna University of Management in Bulgaria and Michael Bond of Hong Kong Polytechnic University conducted the study in Springer's Journal of Happiness Studies. Minkov and Bond used data from three waves of the nationally representative World Values Survey (2000 -- 2014). They calculated the average national percentages of respondents who unambiguously reported being "very happy.' The authors found a strong connection between a nation's happiness and the presence of an allele called amide hydrolase. Nations with the highest prevalence of the allele include Ghana, Mexico, Nigeria and Colombia. Lowest included China, Thailand and Taiwan. Interestingly, Northern Europeans had a much higher incidence of the allele than Central or Southern Europeans. As well as genetics and climate, other factors include economics and political issues in the countries surveyed. Lead Image via Showbiz411