For the fiction writer, this means that dumping a problem on your character's foot will not ensure any particular action. Your character won't act unless he or she is motivated to act, and motivation requires more than "just the facts, ma'am." It requires a bunch of internal factors that can be summarized as "values" but--for the writer--need to be teased apart because they are all--severally and together--motivators for your character to act and react in response to events. So the most important things to know about your character are internal things, things that make him/her behave believably in human terms, not just physical-science terms.
Characters all come with intrinsic, constant traits (race, gender, biochemistry, etc.) and extrinsic, environmental traits (the intrinsic as modified by experience.) By inheritance, each person has a range of adaptations possible to him/her in different environmental situations...the more constricted the environment (in terms of both physical resources and social ones) the less you can tell what the real potential of that person was. But that range is not infinite: no amount of perfect nutrition or medical care or anything else would have made me a six-foot-four blue-eyed blonde male. The more the writer understands about human biology and psychology, the more skillfully he/she can imagine and construct characters with believable complexity of traits and experiences....and thus, with more layers of motivation, arising from many different levels of their being--from the core biological drives to the highest-level, most transient effects of, say, fashion. The more layers of motivation a writer can tap, the more ways to connect character to plot, to make the character feel real and complex.
Everything we do, we do because of some motivation, and that motivation is beautifully mathematical--a balance of competing forces or vectors (vector calculus, if you will.) I am sitting here writing this not because of a single compelling drive to explain character development...but because, of the many possible actions which I kindasorta want to do, and think I should do, this is the one that balances the other motivations the best. I'm not just doing this because I want to--I'm also doing it because I can avoid doing something else (several somethings else) and this is an excuse which lets me feel good enough about myself (oh, gee, I'm helping others--that's worthwhile, right? So I don't have to do X, because I can do Y...) to not do the other things. We all have dozens of things we might do at any moment--and our actual actions are the vector sum of all the influences, internal and external, that bear on the moment. We are hard-wired for two things: first, we are all hardwired to repeat experiences that give pleasure, and avoid those that give pain (positive and negative feedback)...but second, we are also hard-wired to pay more attention to the novel, the unexpected experience. These can conflict, to produce the individual who ignores or seeks out experiences that are unpleasant because a) it's become familiar enough to be tolerated or b) the drive for novelty/unexpected overcomes the drive to avoid pain.
So in a story, the characters act for a reason--their reason. Where did that reason come from? What are the factors that sum into that action? And (most important for the writer) how can we use those potential reasons and factors to make a story work?
The longer the story, the more you have to play with, but in any story (even a short-short) you need more than one level of motivation to make it the best it can be. Let's look at several (which should suggest to you that there are even more, if you need them.)
Physical: on the physical level of motivation, you have the basic biological needs and their associated drives: the need for air, food, water, space in which to exist (habitat, if you will), and avoidance of adverse stimuli such as pain and death. Also on the physical level are bodily functions such as excretion and sex. Choking or suffocating characters will seek air; hungry characters will seek food; characters crammed uncomfortably into a space will try to get out; characters will try to avoid pain and death. Unless there's another competing motivation...because humans will, at times, find something else more compelling than a desire for food or a fear of pain.
Social: here you find the motivations common to a particular social situation--at every level from familial to national/cultural. Cultures set the values that connect facts to actions: hunger to eating or not eating at certain times or particular foods or with certain people or with hands or anything else. You'll find multiple levels of social motivation: the unconscious response to early social conditioning that makes it hard for most Americans to eat "bugs" (eeeuw!), the engrained beliefs about gender, race, ethnicity, religion, the prevalent dominance structure and acceptable attitudes about it, and very conscious awareness of what is likely to produce the best social result...which clothes to wear to work v. play, which cultural icons to admire openly, etc. Acceptance, rejection, cooperation, rebellion, dominance games, ambition--arising partly out of individual biology, but also out of the experience of social interaction from infancy on up. The same objective events have very different effects on the insides of people...one person falls off a horse and never rides again; another falls off the horse (maybe even the same horse the same day) and hops back on without a qualm. Not only does the physical experience vary (one may be more sensitive to pain, or have a better sense of balance) but the social experience will vary (who got laughed at, who got sympathy, who had a previous experience which made being laughed at or getting sympathy different from the other?)
Emotional: On the inside, individual to each character, experience (including social experience) is processed differently and leads to a different balance of emotions. Parents and teachers know that one child reacts to a scolding with angry defiance and another with sadness...the same level of scolding. Innately, from birth, personalities are different, and experience can either reinforce that difference or smooth it out--but will not change it. The same basic emotions--joy, sadness, fear, disgust, satisfaction--are attached to different things, in different amounts, in different people, for different reasons.
So in a story, a character may, dealing with the problem you give him/her, react from any of these levels or sublevels, or any combination of them, just as you do. If you have an hour for lunch, you may be juggling errands (the bank, the post office, the dry cleaner's, buy a gift for a friend's birthday) with the need to eat (especially if you skipped breakfast), the awareness that you need to eat carefully because of a health problem, the knowledge that the only places to grab a quick meal near your errand-destinations don't have the food you should eat, guilt over having skipped breakfast and not having packed the lunch you should be eating, concern over gas prices and a struggle to find the most efficient route through your errands, resentment for being expected to do so much in so little time, resentment at not being able to just get a burger and malt without feeling guilty about that, too. What do you eat for lunch? More importantly, what would your character do? Larry the diabetic, let's say, who's divorced, with two kids (one of whom has a birthday in two days), with credit card debt, a bank account nearing zero, only a quarter tank of gas in the car, bills he has to get in the mail today or else, payday's not until next week...you can see that you can tie what he actually does to physical, social, and emotional motivators. Will he buy his kid the expensive toy the kid really wants and risk more financial problems? Will he blow his diet because of frustration? What kind of person is he, at all levels?
When we get to plot, you'll see that this kind of understanding of your character's motivations lets you maintain tension on various levels at different times, so that the reader feels the pull of the character, but isn't being held on the same level throughout. Sometimes your character's facing a physical threat (maybe--not in all stories), and sometimes a threat to self-respect or social position or financial security or relationship stability. Just when the character is triumphant in one thing, something else may go wrong (as it does in real life...immediately after my first book came out, when I was jubilant and heading for a bookstore to sign copies--the muffler fell off the bottom of my car, loudly and publicly and expensively.) Plots need setbacks and complications, but they should not all be at the same level.