(update on this post)
I have received a few baffled comments and emails, wanting more explanation for how this mysterious magic trick works.
I won't assume you read my reply in the comments section, so here is my update.
(I was recently obliquely chastised for making a comment on a post without having read through someone's comment section. I read blogs because I am interested in what a certain author who captured my attention before might have to say again. Not so much what their 245 advice-slinging commenters have to say.)
When I was shown this technique, the therapist/ECI actually held it in front of him as if the bowl would catch the barf. She also acted all like she just didn't care if he threw up or not. So he was thrown OFF completely!
This was a valuable modeling lesson for me to watch - I instantly saw that our reaction had been way too exciting and motivating for him.
The presence of The Bowl makes him (and, apparently, almost every other child who gets offered The Bowl) get so distracted or angry that he doesn't throw up anymore. She said a few kiddos do throw up - but only once or twice in the bowl. When they realize there is not going to be any reaction or clean-up flurry, they generally give up the barfing!! I think she has a 100% success rate.
As far as the color? The bowl does not have to be blue - it can be any bowl, any color. I have found that, for my little puker, it helped to have it be the same bowl each time - because there was no mistake in his mind if I was bringing him snacks or offering him the dreaded barf-bowl.
I don't know why it works so well, but it does.