There are 4 paragraphs spread out over something like 1600 vertical pixels.
When I saw that the video was not only in that same "clown on acid" visual style, but 2:45 long, I bailed hard.
Pairing mental associations seems like the kind of thing that should be demo'd on the home page, not buried behind a signup wall.
In other words, you need to provide value upfront. By upfront, I mean within the first 500 pixels of page height.
edit: I'm not affiliated with these guys, but they showed up on HN recently and I found their site compelling. http://www.timeful.com/
But when I looked at, it wasn't so great. I don't know what is missing or what is wrong, maybe the ideas I saw weren't mine. Or maybe the transition between "anything you think about" and the paper is not that easy.
Fun fact: Brian Eno played with an early prototype of Seenapse and gave us some feedback too :)