As stated above, the field "Title" of a contact (where you can choose Mr., Mrs., etc.) is restricted to users of the groep "base.group_no_one". (Which is the ID of the Technical Features group.)
Code of this field:
<field name="title" domain="[('domain', '=', 'contact')]" groups="base.group_no_one" options="{"no_open": True}" attrs="{'invisible': [('is_company','=', True)]}"/>