Medical science has elucidated many brain functions. This led me to question certain "mystical experiences". We know from various studies that these experiences can be induced in individuals (i.e entheogens). Also, patients suffering from temporal lobe epilepsy claim to have profound feelings after a seizure, as if they had experienced God, and they no longer see life as meaningless.
Are these real divine experiences, or mere delusions? How does one know if meditative experiences are "real"?
Right now there is a lot of research going on at Stanford University that is looking at this question of why some people have transformative experiences and others do not.
They are looking into the neurobiology of it and perhaps will have a scientific answer for us soon re: what happens during some of these profound biochemical and electrical changes that happen and effect people.
Of course we also know that there are neurochemicals that are released that do change our state of "feeling" but not necessarily our state or level of consciousness. A person may have a profound change in his or her attitude w/o necessarily having a true superconscious experience, which we know can only occur through communion with the Divine.
Swami Kriyananda mentions throughout his teachings that experiencing deep, calm, peaceful feeling throughout meditation is a good sign that one is experiencing Superconsciousness.
Yogananda says that, "When bliss comes over you, you will recognize it as a conscious, intelligent, universal Being to whom you may appeal, and not as an abstract mental state."
Still, the question/answer of what is "real" can only be truly known by one who has experienced the Superconscious.