Hahaha. You'd get way more than 100 neuroscientists rightfully saying that this is pseudoscience.

IIT is what Massimo Pigliucci terms "almost science". They want it to be science. But it's not: too many assumptions, basically no key tests. As pseudosciences go, it's pretty thoughtful. But I'd have signed the letter.

However, the evidence for collective consciousness is much worse. We can talk about specific papers if you'd like, but keep in mind that almost every psychology experiment ever would be messed up if the assumptions about consciousnesses being independent were badly wrong. And it'd show up in experiments (controls wouldn't work). If they're only mostly independent, well, you can always dial down the level of collectivity until it fits within the error bars around zero.