So the psychologist to test the first group of volunteers by the selected objects from the table in one room to remove it through the door and then through another which lead back to the first room.
So psychologists tested the volunteers first select an object from a table in one room to get it through the door, through which again leads back to the first room.
So psychologists test volunteer first group by select objects from the table in one room to get it through the door, then through another, which brought back the first room.