With college kids home for the summer, and summer visitors coming and going, human territoriality comes to mind.
Human beings are not that different from squirrels - both species claim particular places as their own. People have a fundamental need for a space that's recognized as belonging to them. Even when we're just somewhere temporarily, we claim part of wherever we are - jackets slung over the back of library chairs keep other people out of "our" spots and when we were in school, territoriality, among other things, kept us sitting in roughly the same seat each class period - even when seats weren't assigned. The need to have other people recognize a space as belonging to us is so strong, that we even touch the edges of our dinner plate as it arrives in front of us in a restaurant - just in case anyone tries to get too close to the beef stroganoff we ordered.
When we're in our own territory our stress level goes down - unless someone seems to be impinging on it. We can relax, reduce our attention to the world around us, reflect on our experiences, and order our thoughts. We need to do these things to thrive.
To make our territories clear, we personalize them. Personalization can take many forms - sometimes we scatter photographs that have personal meaning to us through a space - North Americans and Europeans are particularly likely to focus on things that they can see, at the expense of info collected from other senses, so visual cues are particularly desirable there. Territorial cues don't have to be visual - a scent or a song (sung live or recorded) that drifts through a space will do the trick as well. Drifting things are particularly likely to travel into someone else's territory, which is, at minimum, problematic. Even turning on or off a light, or changing the ambient environment in some other simple way, establishes a space as ours.
People also mark territories with walls or other spatial elements. Sometimes the edge of a carpet does the trick in a workplace, or an archway separates claimed areas in homes. Nothing says "this is mine" better than a door.
Not just individuals need territories, groups do as well. Clubs have clubhouses. Members of religious congregations bond even more intensely through united concern for their place of worship. Teams at work bond in spaces that are designated as theirs.
Speaking of workplaces - territories are particularly important there. In modern offices, workplace territories are a direct way to communicate to others - they are free of the empty platitudes of mission statements, personnel policies, and job descriptions. They tell employees what the organization thinks about them, and illustrate to the organization and co-workers the sentiments that the "owner" of a space reciprocates. Everyone in the organization speaks the same spatial language so space-based communication is clearly understood by all. Workplace territorial invasions real (others let their file folders creep into our space) or symbolic (being asked to take the Beanie Babies home because they annoy team mates) regularly escalate quickly beyond the original situation.
So, how does this all relate to those college students and summer travelers? Give them a space to call their own - and be understanding when they do take over the place that you've given them. Students home for the summer may need to rearrange the furniture in their old room, hang some new stuff on the walls or change the physical form of the room in some other way, play some loud music, or eat foods that smell particularly noxious in their room, just to reassert their spatial rights. If you are lucky, the claiming will subside before they return to school.
People visiting you will spread out the things that they're traveling with in the area where they're sleeping. This is a lot less stressful for you if they're sleeping in a guest room than it is if they're on the living couch. They will do a whole assortment of things to change and customize "their" environment. Know that their fiddling with the lights and the air conditioning is also part of their effort to feel comfortable in your home. Be patient with them - you did the same sort of things the last time you spent time in their house.
Sharing our homes with others is really difficult - our homes are our most private and personal territories. If it all gets to be too much, retreat into your own room and close the door. If you're lucky the walls are thick enough to block out the music and the door fits securely enough to cut off smells. And your guests will ultimately leave. Eventually, your home will be entirely yours again. For a while.
