Buddhism is a virtual storehouse of different meditation practices, and as it has grown more and more popular, those practices have piqued the interest of Western researchers. At first, researches assumed that all styles of meditation were pretty much the same. After measuring the changes in meditators’ physiological states, they found a lower heart rate, slower breathing, and an activation of the parasympathetic nervous system that produces a “relaxation response.” Then as researchers became more sophisticated, they began to use a two-part classification commonly found among Buddhists themselves. The first technique is called shamata (tranquility) meditation and involves selecting an object like the breath or a colored disk and focusing on it single pointedly. Consequently, researchers sometimes called it “focused attention” or concentration meditation. The second technique is called vapassana (insight) meditation. In the Theravadan tradition, which most of the researchers were studying, vapassana involves opening up one’s attention to become aware of all the content in the mind and especially the way the objects of attention arise, abide for awhile, and pass away. Researchers called that type of meditation “open monitoring” or “distributed attention” meditation. When meditators were tested, they found that both kinds of meditation still produced an activation of the parasympathetic nervous system consistent with the “relaxation response.”
Some researchers also classified the visualization practices of the Vajrayana tradition as a type of focused attention, since meditators focus their mind on a complex visualization with an enlightened being at the center, which they eventually imagine themselves to become. However, when researchers actually got around to measuring the physiological effects of this meditation, they found that those practices do not induce a state of greater relaxation and tranquility after all, and that it is the sympathetic not the parasympathetic nervous system that was being activated. Furthermore, subjects also showed a dramatic increase in performance on cognitive tasks after meditating—something that did not occur with the Theravadan techniques. It turns out that that the same thing also happens with the Vajrayana meditation known as dzogchen that researchers had classified as a kind of vapassana meditation. Obviously, much more research is needed, but it seems clear that there are many more different types of meditation than researchers initially recognized, and that they produce very different results. While some types of shamata, with its emphasis on tranquil alertness, is practiced in all the Buddhist traditions, it is clear that other styles of meditation may take meditators into more energized states of awareness.