What you expect to see depends upon what you have set for the OWD.
Organization Wide Defaults apply to your entire org by default. When defined as:
Public Read ONLY - Anybody(All users having access to that particular object) in your org. can read the records of the object.
Public Read Write - Anybody(All users having access to that particular object) in your org can read and write the records of the object.
Private - Only the owner of the record can modify the record.
So if you say, there are no sharing rules, role hierarchy, manual sharing etc. and OWD is set to PRIVATE only the owner of the record can view the record. Not even his manager, and no one in the same role as well.
The exception to this will be:
Any user having "View All Data" or "Modify All Data" enabled on their profile. For Admins this is always set to true and hence they can see and modify all data.
For users if in their profile under Object Settings, if for a particular object "View All" or "modify All" is enabled, they can see the data.