We all do it. We can't help it. We're predominantly visual creatures. (The visual area at the back of our brains comprises 30 percent of our cortex.) The wrappers in which things come not only powerfully affect what interests us but also how we react to the contents we find inside. This certainly holds true for companies, which can convince us with professional-looking marketing materials, web sites, and offices that they produce professional-quality work. It also holds true for books, whose covers draw our attention, create an expectation that excites us, and suggest a certain quality of writing. Certainly the truth is laid bare once we start reading (just as the truth about a company's quality is laid bare soon after we hire them), but if anyone doubts how their expectations for a book they're about to read are affected by its presentation, I'd challenge them to examine their initial reaction to a book not with an unattractive cover but with an amateurish one.
This is also true to some extent with the way we react to people. By this I don't mean that we're more interested in and think more highly of attractive people (though research suggests both are true). Rather, I mean that our expectations of others are triggered by not only how they look but how they present themselves overall (what clothes they're wearing, whether they're clean-shaven, their accent, and so on). This wouldn't be a problem by itself, however, if it weren't also true that we're so often more influenced by our own biases than we are by actual evidence. When we have a powerfully positive or negative emotional reaction to someone upon first meeting them—often due to their overall presentation—it powerfully affects our reaction to the "content" we find inside, meaning their personality and character. As Proust famously wrote:
We pack the physical outline of the creature we see with all the ideas we already formed about him, and in the complete picture of him which we compose in our minds, these ideas have certainly the principal place. In the end they come to fill out so completely the curve of his cheeks, to follow so exactly the line of his nose, they blend so harmoniously in the sound of his voice that these seem to be no more than a transparent envelope, so that each time we see the face or hear the voice it is our own ideas of him which we recognize and to which we listen.
We all carry around with us conclusions we've drawn about other people through which we filter everything they say and do. Certainly over time a person's actual personality and character alter these conclusions, but even then our conclusions often remain highly biased. Further, we seem to err mostly on the side of overestimation, thinking people far worse—are far better—than they actually are. It's the rare person, in my experience, who looks more skeptically at his beliefs about someone than at any evidence he observes that contradicts them.
But that, I would argue, is exactly what we should do. It takes more cognitive work—which is undoubtedly part of the reason so many of us are so reluctant to do it (as Daniel Kahneman famously asserted, we're all cognitively lazy)—but people are not only more nuanced than we typically acknowledge, but also change more often than we realize. If we really want to understand our fellow human beings accurately, we must allow them to surprise us, to contradict what we think we know about them. Like good scientists, we should cling to our theories about people only loosely and always be willing to revise them in light of new data. The package in which people come to us may be attractive or repulsive, but if we exert a little effort—like opening a book and browsing its contents before deciding whether to buy it—we can see past our visual biases to the truth. That way, we'll be far less likely to exclude from our lives not only a quality person—but also a quality book