Microsoft's voice-activated personal assistant that is baked into the company's Windows Phone OS will be not be capable of speaking to anyone under the age of 13, according to CNET.
Why? Because Cortana is capable of collecting data on its users in order for it to better assist users in finding answers to their questions. This data is collected and sent to Microsoft services, meaning the voice-activated personal assistant falls under the purview of United States' Children's Online Privacy Protection Act (COPPA) of 1998.
COPPA restricts the information that children share online, or data that can be collected from them, without parents' permission. But for now, Cortana sits in the beta state, with the issue on a forum for Windows Phone developers, with one developer wanting to help his daughter use Cortana. The bigger issue at hand is that Cortana can only know a users age if she is told their age, it can't recognize grade voice patterns for someone's age... yet.