After only two weeks of online training, participants who practiced compassion meditation every day behaved more altruistically towards strangers compared to another group taught to simply regulate or control their negative emotions. What’s more, the study is the first to link these behavioral changes with measurable changes in brain activity, shedding light on why compassionate thoughts may actually lead to compassionate deeds. “Doing these kinds of exercises is a little like weight training—the compassion ‘muscle’ is strengthened by practicing with people of increasing difficulty, like increasing weights over time,” writes lead study author Helen Weng. After the experiment, Weng’s team made the compassion trainings available for free to the general public. As of April 2014, over 3,700 people have downloaded the compassion meditation training in over 60 countries.