When Middle Son was a toddler, he ate a limited range of food. Very limited. I remember once when we had a sitter come to watch him, MomC told the sitter that there was a list of the foods he would eat on the refrigerator. The sitter laughed and said "you can list all the foods he eats on a sheet of paper?" I responded that actually we could list all the foods he ate on a post-it.
Middle's diet at the time consisted of foods that were brown, dry, and crunchy. He ate dry toast, cereal with no milk, cookies, crackers, and chips. NOTHING else.
For a while Middle worked with a "feeding therapist". She was an occupational therapist who specialized in sensory issues around food. I remember the progression that she went through--size, color, texture, taste. She took goldfish crackers (which he would ate). Then she got larger goldfish and coaxed him to eat those. Then she got different colored goldfish. Then she put a little peanut butter on them (which was texture and taste at the same time).
Eventually, he started trying other things. First he would touch them with his hands. Then he started putting them in his mouth. Then later he started chewing on them.
But he wasn't ready to swallow. So he'd chew on them and spit them out on the floor. My mother-in-law tried to stop him and MomC and I both jumped to intervene. We were really excited that he was chewing on a new food and didn't want to do anything to discourage it.
I had never imagined that I would see spitting food on the floor as a good thing. And then I did.