My view on it..

Like most people I was totally confused..until the part where the one friend gets scalped, I saw them almost in a state of euphoria... that no matter what they were doing it felt right. It felt okay. To understand this type of feeling you have to have experienced some sort of addiction I have experience with this and I know first hand how it feels to be in such euphoria that nothing can be upsetting or wrong. So I figure the mom some how encountered an alien in one way or another. Then Tyler spread her ashes that materialized into the "corridor"and in some way or another this thing unlocks the mind in all kinds of wonderful but also terrible ways. I think they were so caught up in this "high" they felt that they would do anything to keep it (putting Tyler's pill down the drain) and it just made everything seem okay. That's how I took it at least ..I could be totally wrong though. However no one seems to really know what was going on ..I pretty much think they were all just tweaking out from the feeling they got from it. I don't believe it was all in Tyler's head or they just linked to Tyler's mind. The scene with Lee (the hunter) kind of made clear that this was no mind trick.