"I've got no option but to sell you all for scientific experiment."
About 10 months after our first was born, we got an offer from the child development program at Notre Dame to bring our child in for observation and developmental testing. They'd give us $20. So we joked about selling her for scientific experiment.
We got to sit behind a two way mirror and watch them interact with her. She couldn't talk yet, but could sit up. So they sat her in a chair across a little table from the person conducting the testing. There were a bunch of little red blocks on the table. The tester never said a word. She took one block and set it in front of herself on the table. Our kid looked at her, then grabbed a block and set it in front of her as well and looked at the tester. So the tester took another block and stacked it on her own block and looked at our kid. Our kid looked at her and stacked another block on her own block and looked at the tester. The tester repeated this 3 more times. So did our kid. Finally the tower of blocks fell over and they both started laughing.
That was the test. They said she did better than most for her age, so we enrolled her in medical college immediately.
Just kidding. There were a few more tests, and we took her back every few months for a couple years. When we had our 2nd child, they offered us a program for sibling development, so we did that as well. Each time it was $20 and we'd go out for pizza.
It was just interesting to see your kids pass these developmental milestones in everyone's life. Kinda reassuring to new parents.