DS 4 also has a great memory. He started with numbers a nine months,then came letters,solar system, dinosaurs, states and capitals to name a few. I am not sure how much he has retained of these things but his true love is words.
He started learning words at 13 mos. And at 19 mos. He was tested by a reading speciialist at mid first grade level with excellent comprehension. Now his reading vocabulary is at sixth grade level. He has his own system for figuring out the words. A researcher at our local university who has tested him
Thinks it is based on chunking parts of words he already has memorized. If DS
Has seen a word once, he never forgets it.