I've been talking more about the mythological aspects of character development in talking about archetypes (though there's a lot of Jungian psychology in there, too). But one of my favorite things to do to help me learn to find ways of developing and depicting characters is through psychology. I'm always looking through the library's psychology section to find books on interesting aspects of personality. One I found recently, called Snoop: What Your Stuff Says About You by Sam Gosling, Ph.D., struck me as a wonderful characterization resource.
The author, who's on the faculty at the University of Texas, focuses his research on trying to analyze personality based on a person's possessions and surroundings. As writers, we have an advantage in that we already have a pretty accurate assessment of our characters' personalities and can reverse-engineer their surroundings and possessions to reflect and depict that. I'd recommend reading the book if you find these ideas interesting, but here are a few tidbits I pulled from the book that I think might be helpful for characterization.
One category of possessions is what the author calls "identity claims." These are deliberate symbolic statements about yourself. They can be other-directed, so that they're about how you want to be seen by others. That includes things like bumper stickers (since you don't spend a lot of time looking at your own car's bumpers) or tattoos (since many tattoos are located in places that can't be easily seen by the person with the tattoo). Or these things can be self-directed, so that they reinforce how we see ourselves, like family photos, reminders of past success or personal keepsakes. This may be a message that's meaningful only to the person and obscure to outsiders. You can often tell the difference based on where they're placed. Other-directed identity claims are mostly where others can see them -- pictures on a desk facing the visitors' chairs, posters on the outside of the office door, in the office, in public spaces at home, like the living room, or in the front yard. Self-directed items will be mostly where the person can see them -- photos on the desk facing the desk chair, a poster the person can see from his/her chair but that's not obvious to others, at home, in private spaces at home, like the bedroom or in the back yard.
When analyzing these, look for matches or discrepancies. Someone who's trying to be something he isn't may send totally different messages through other-directed identity claims than he sends through self-directed claims. To depict this in a book, you might have a distinct difference between that person's public spaces and private spaces. For instance, someone may want people at work to think of him as a high-powered, super-successful executive who lives, eats, breathes and sleeps business, so he'll have an office full of status symbols designed to impress visitors, like awards, diplomas, a big desk, photos of himself with important or famous people, etc. But if what's really important to him is his family and he fears that being a family man will make him look weak in business, he may have things that remind him of his family where only he can see them -- the photo of his family on his desk may be turned to face him, he may keep his daughter's drawings folded up in his day planner, and the keys to his status symbol car may be on a keychain his son made in Scouts.
Another category of possessions are "feeling regulators" -- things that can influence mood or emotion. These are things that calm or rev us up and may include colors, keepsakes, photos, inspirational quotes and different kinds of music. One interesting thing that the author found is that people with those inspirational or motivational posters on the wall tended to be more neurotic.
Then there's the way behavior reflects in possessions or surroundings. The author calls this "behavioral residue" and says that it's not nearly as conscious as these possessions. It's the result of habits or everyday actions -- are things put away or left out, what things are left out and what things are put away, how are things arranged. Trash is a good source of behavioral residue -- what you find in a person's trash can tell you a lot about them. Oddly enough, in spite of how often this shows up on character-development worksheets, the contents of a person's refrigerator don't actually tell you much about his or her personality, unless it's something really, really odd. That's because refrigerator contents are so transient and vary depending on how recent the last shopping trip was or if the person has just cooked something. You'd have to study the refrigerator over time. One look doesn't tell you anything about the person, unless it's filled with something like blood. One of the best places to analyze someone's personality is in the bedroom -- no, not in that way, but because that's generally a private place and a place of comfort and safety, the possessions and surroundings in the bedroom are most likely to reflect the way the person really is.
You can also read a lot into how possessions are used (or not) -- someone with a really messy desk that has a lot of office organizational tools on it may value the idea of organization but may not have achieved it. Likewise with someone who has a lot of bath salts or bubblebath in unopened jars and candles in the bathroom that have never been lit. That may be someone who feels like she ought to relax more often but who hasn't found the time. Things that are owned but not used are a sign of what the person aspires to -- or, if they're a gift, of what someone else thinks they should be.
While we may be able to reverse engineer our characters' surroundings based on their personalities, remember that the other characters in a story can't and have to make their own guesses, which may be right or wrong. They need to take into account the context of the item -- where did it come from, why does the person have it, does it even belong to that person? You could get the totally wrong impression by judging someone on the basis of an item that was a gift or that a friend left behind. One odd quirk of human nature is that we're likely to notice the weird thing that doesn't seem to fit first, and then interpret everything else based on that. The author mentioned a situation in one of his studies where the room being evaluated had a pair of high-heeled shoes lying in the floor. The researcher evaluating the room decided that meant it was a woman's room and evaluated everything else accordingly. But the room belonged to a man who'd had an overnight guest who'd left her shoes behind, and everything else about the room indicated that it belonged to a man, but because of that first impression, the researcher overlooked all the other clues. Another way to get a more accurate impression is by looking for patterns in various aspects of the person's life -- at home, the car, the office, various parts of the home, clothing, musical tastes, etc.
Sometimes characters may deliberately try to create a false impression of themselves, and this isn't actually all that easy to do beyond the most superficial levels. It's difficult to fake the results of long-term patterns of behavior. For instance, a man trying to make a woman think he's sensitive and emotional might put a book of poetry on his nightstand, but if the woman actually looks at it, she'll notice if it's never been opened, if the pages stick together because they've never been turned, if the book doesn't fall open to a favorite poem. To make the book look like it really belonged to a sensitive poetry lover, he'd have to actually spend a lot of time reading the poetry. There's also the problem that someone trying to fake it won't know all the things that someone who's truly into it would notice. The author points out the difference between a "tidy" house and a "tidied" house. There's a difference between a place that's kept habitually clean through tidy habits and a place that's been frantically cleaned. A woman who's a bit of a slob may desperately clean her house to impress her neat-freak mother-in-law, but the neat freak probably won't be fooled because she'll recognize the lack of systems for maintaining that level of neatness, and there are things that would be obvious to a neat freak that a natural slob wouldn't even think needed to be cleaned. The place may look spotless to the slob but may still be a total mess to the neat freak.
I suppose all of this still comes back to action defining character, because all of these things come as the result of actions characters have taken and choices they've made. They're just very concrete ways to show patterns in a character's life that tell you a lot about them.