Cognitively-Based Compassion Training was developed at Emory University. Their studies used non-meditators in an eight week program. With testing using fMRI brain scans and empathy testing they found an increase in test results as well as an increase in neural activity in areas of the brain important for empathy.
It is interesting to me how many of the studies that I come across are eight week long studies. This is usually because the work is based in the Mindfulness Based Stress Reduction course developed by Jon Kabat-Zin which is itself eight weeks long. But in this case, it was a separate study.
Eight weeks seems to give a lot of benefits. But there are other studies that show even shorter amounts of time can produce results.
Compassion meditation may boost neural basis of empathy, study finds.