Click on Options at the right of the window. In the resultant window, click on the Login tab. Under that tab is an option to Allow Alternate Password. At this stage, the only alternate allowed is voiceprint, so you don't have to worry too much about the drop-down menu. The fact that there is a drop-down menu is intriguing, though: what will Apple introduce as further alternatives to typed or spoken passwords? Fingerprints? Retinal scans?
Also in this box is the option to allow users to speak their names. I've tested this using dummy accounts with similar names (Matilda, Mark, Matthew, etc.) and, frankly, it's a little dodgy. I wouldn't bother.