Yes,
you can use conditions, example:

I have a select fields with these options:
1|Author
2|Manager

now I set these conditions on this field:
- Condition 1: if equal to custom value "1" add to usergroup "Author"
- Condition 2: if equal to custom value "2" add to usergroup "Manager"

Now user can control own group with a simple select field

NOTE 1:
conditions have two ways so for example if user is already author and choose manager, he will be removed from group author, this because condition 1 do this, if equal to custom value "1" add to usergroup "Author" else remove from usergroup "Author"

NOTE 2:
Registered group is mandatory for all registered users, this group is set into Users->User Manager->Options->New user registration group parameter