NSNotificationCenter: Do objects receive notifications on the same thread they are posted?

The short answer is yes... "Regular notification centers deliver notifications on the thread in which the notification was posted. Distributed notification centers deliver notifications on the main thread".

However, Apple has docs on this very subject that you may find helpful, and from which the above quote was pulled:

Notification Programming Topics: Delivering Notifications to Particular Threads

Just bothered to look it up myself, shameful:

From the class reference: NSNotificationCenter posts all notifications synchronously

Also, if you prefer, you can use NSNotificationQueue to post notifications asynchronously