Originally Posted by HowlerKarma
[i]
2) nothing upon DEMAND; skills are demonstrated intrinsically or not at all.


This was my DD for many years when she was young. For example, she spoke VERY early and well, but the day I put her on the phone with my mom and said something like "show off for grandma" she stopped speaking for close to a year and only started again when she was capable of perfect complex sentences. She'd mutter under her breath, but nothing else until she was ready.