Which of the following is the factor that determines human beings’ psychological space needs?

　　Now, I’ d like to talk about psychological space.
　　Not everyone in the world requires the same amount of living space. The amount of space a person needs around him is a cultural preference, not an economic one. Knowing our own psychological space needs is important because they strongly influence your choices, including, for example, the number of bedrooms in the home. If you were reared in a two-child family and both you and your sister or brother had your own bedrooms, the chances are, if you have two children or more, that you also will provide separate bedrooms for them. In America they train people to want their own private rooms by giving them their own rooms when they are babies. This is very rare in the world. In many cultures the baby sleeps in the same bed with his parents or in a crib near their bed.
　　The areas in the home where people gravitate also reveals a lot about psychological space needs. Some families cluster, and the size of their house has nothing to do with it. Others have separate little niches where family members go to be alone.
　　Although it is tree that psychological space needs are not determined by economic factors, they sometimes have to be modified a little because of economic pressures. It is almost impossible, however, to completely change your psychological space needs.