What lvl of skill for a Frontier character to be called a doctor?

What level of skill should a frontier citizen have to be called a doctor? <br /><br />For example I'm messing around with the Cassidine Jones and the Raiders of Volturnus idea and casting the PCs in the &quot;Indiana Jones&quot; roll who is famously called Dr. Jones&quot; throughout the franchise. <br /><br />With PCs getting a free level 2 science skill to start plus 2 more first level skills it doesn't seem right to accord them the title of Doctor. <br /><br />Perhaps professor? I'm considering using the Triad Intitute of Technology as a sponsoring organization in a very Indiana Jones style adventure with a Volturnus campaign mash up.