As the singing begins, a slow smile begins to spread across his face. He thinks, "this is cool--I like songs." Then the magic line, "happy birthday dear Aidan" and as he recognizes his name, smiles big, laughs, and claps. It's the baby equivalent of, "Oh my god! I can't believe this song is for me! That's AWESOME!"
And then he got to eat cake for the first time, which seems to be another big hit. Already birthdays are shaping up to be a favorite. Forget Thanksgiving and Christmas. Bring on more birthdays.