LotR -- Book 3 - Chapter 04 - Treebeard

[Encaitare]

‘Ents are more like Elves: less interested in themselves than Men are, and better at getting inside other things’.

I always thought that this meant that Elves were not fascinated with themselves, as, say, Sam was fascinated with them, and that they (in general) did not have these great inner conflicts such as Men sometimes did (as seen in Boromir, especially). Instead, they were able to put their time to better use, getting things done rather than sitting about contemplating their navels. This doesn't really sound like Ents to me, though, seeing as they take a long time to do anything. But since they've been around for thousands of years, then I suppose maybe it could apply to the Ents as well.

Or, "better at getting inside other things" could refer to the way they both could communicate with and understand the trees.