I've no idea how this might relate to the findings from the study but my nineteen month old baby has problems with the number four. She recently started counting up to ten. She will recite each number as she moves groups of like objects from one pile/container to another. She didn't count until about two weeks ago, she started counting with us then counting on her own over the last two weeks. She does a very good job, but has a hard time remembering the number four, jumping from three to five. I hypothesised that the game "give me five" by slapping hands might have given special importance to the number five, it seems to excite her a more then the other numbers, not that 'give me five' was a huge game with us.
\0 You realize we have daughters that are pretty much the same age? My daughter is 21 months. I've not noticed any hesitance to say "4" but I have noticed that she likes the number "5" and I'm guessing it's for the reason you outlined. She's been saying (singing) her ABC's (via the alphabet song) lately and it's funny because LMNOP is essentially one letter to her. I'm trying to teach her the separation. The other day she was really in to her own shadow. Watching a child figure that out is a pretty fun thing to witness. This is such a fun age that I can't stand to be at work for the fear that I'll miss something. edit: Counting to ten at 19 months is really great, especially if she's correlating the numbers to objects. Whatever you are doing, keep it up!
Me too. I was very excited that in one swoop I had figured out how to play both on my guitar for her.