But as twin studies revealed the awesome reach of genes and the relative unimportance of the family environment that siblings share,30 the ancient happiness hypothesis grew ever more plausible. Maybe there really is a set point31 fixed into every brain, like a thermostat set forever to 58 degrees Fahrenheit (for depressives) or 75 degrees (for happy people)? Maybe the only way to find happiness therefore is to change one’s own internal setting (for example, through meditation, Prozac, or cognitive therapy) instead of changing one’s environment?
