For about 30 minutes, you existed as a single cell. Nine months later, you were born with over 300 bones in your body; yet, you will die with 206.¹ Twenty-two of these form your skull and contain twelve paired cranial nerves, the second being your optic nerve. At just one millimeter wide, it connects your brain to everything visual in the world. On a clear night, your eye can detect a candle’s flickering light 30 miles away.² Your sense of smell is no less impressive; the human nose can detect a single drop of perfume in an adjacent room, as well as thousands of scents.³ Each of your fingertips can touch your thumb, and you blush—both of which are unique traits among primates. You hiccup for no apparent reason, as well. Excepting those with physical and cognitive disabilities, people universally laugh, cry, sit, stand, look, touch, and feel. We have been this way for thousands of years. It is both exhilarating and humbling to realize just how similar we all are.

With humans sharing so much in common, you might wonder why designing for them can be such a challenge. After all, you are one of them, too. Knowing what users want and how they behave would seem to be implicitly understood. If that were the case, we would not even need to concern ourselves with user experience. We would know everything already. However, despite our similar physiology and neurology, human beings do have differences.

People differentiate themselves through an expansive range of cultures, educations, aptitudes, social norms, etiquettes, and taboos. Some distinctions are subtle, but others are not. A newborn Bulgarian baby may be spat upon for good luck, whereas a Finnish baby may spend its first few nights sleeping in a government-supplied cardboard box.⁴ Members of the South American Yanomami tribe eat the ashes of their dead relatives, whereas the Houston-based company, Celestis, launches your loved ones’ ashes into outer space (see Figure II-1). Although we have similar starting points, where we go from there often takes wildly different directions.

We have similarities. We have differences. Designing a single, optimum experience to serve everyone is impossible; you’d be too busy handing out wet wipes and keeping everyone from launching one another into orbit. Nevertheless, we realize design solutions when we focus our efforts on a particular set of human beings with a particular set of goals.

In this section of the book, we examine the physiological and psychological factors to consider when designing experiences. We discuss how we sense and perceive our world, how our attentions wander, how we are pushed and pulled by persuasion, and how users recognize information today and recall it tomorrow. We even talk about the benefits of being lazy. But, for now, let us be ambitious and start at the very beginning of what makes an experience—perception.