I wouldn't doubt that we can impact how the mushrooms grow and perhaps how they effect us and others with our energies. I feel strongly that the mycilium is a sentient entity. They choose what they will teach you, and when.
I also believe that MIND SET and SETTING have huge effects on the trip, especially once you get over the 3-4g mark as long as they are good mushrooms. Many people never eat more then an 1/8th, or never eat more then an 1/8th once
. Average mushrooms an 1/8th is a good trip, but not usually super heavy. I've had some pretty heavy trips off 4g of good mushrooms, but 6-7 was really the zone if I wanted it to get crazy.
When its all said and done I've never had a BAD trip. But in hind sight most of the time things have gotten dark I could directly relate it to something with my mindset or setting.