Even young babies know who's boss

http://www.newscientist.com/article/dn20041-even-young-babies-know-whos-boss.html
In many species, bigger is better. Birds puff their plumage to inflate their perceived size, humans talk about the "big man" on campus, and are even more likely to vote for the tallest candidate in an election. Now, it seems that children as young as 10 months use size as a cue to interpret social hierarchies. Cordes suggests that mental representations of social dominance emerge alongside enhanced locomotion, once children have begun crawling and practicing more fluid movements.

It is interesting and surprising fact that even young babies know how to differ the blocks by size and use size as a cue to interpret social hierarchies.