I'm not claiming that The G is a genius. But given her unfathomable interest in everything that The B does, she is receiving quite an education by proxy.
She listens to everything he says and, whenever he sits down to practice his letters or numbers or finds a book to read, she does exactly the same. She knows all the classroom rules and regulations and has learnt all the teachers' names. She can write her name (and his), can work out the first letter of most words and, in the bath the other night, she counted to 100. She even knows all the planets.
The B is quite clever but the knowledge that The G has acquired from their time together means that she is far more advanced - in intellectual terms, at least - than he was at this age.
Keen to push her boundaries a littler further the other day, I fired up our long-forgotten Nintendo Wii. The 'game' I chose is called Big Brain Academy, a collection of tests and puzzles that, it is claimed on the packaging, is designed to calculate brain power.
This isn't intended for children. Still, it came as no surprise to discover that The G soon had it all sussed out . . .