Sentence:  It is customary, moreover, for those sharing a cabin to while away train journeys chatting on the two bottom bunks, which is likely to jar with many Westerners' narrower conceptions of <WSD>personal space</WSD> and ownership (especially if they have paid top dollar for the prized bottom bunk). 
Meaning of the word marked with <WSD> tags:  The physical space closely surrounding a person, which can lead to discomfort, anger or anxiety if encroached on.