> you either have something to channel or don't

Again, any evidence? What exactly is 'cognitive ability'? A hallmark of the lack of substantive argument is vague terms that can mean anything the speaker likes, and by not defining the term they prevent any substantive critique - nobody really knows what they're talking about (and usually, not the speaker either).

I highly doubt it's all or nothing. While there are likely variations in anything, they can be quite insignificant. For example, everyone, with tiny exceptions, can learn to speak & understand language, and write & read - highly sophisticated cognitive abilities. And they can improve those abilities through education.

These baseless generalities don't show much 'cognitive ability'.

There's plenty of evidence for those who want to learn instead of split hairs.

I'd start with a search on "general intelligence factor".