The diversity in this field is striking. Nevertheless, psychology is a unified science with many assamptions and beliefs. Lest we overemphasize the diver­- the field, let's identify some ideas that all psychologists have in common besides their history and scientific methods.
We have prepared a list of the most important things that contemporary ps­ychologists "know" about human lives. This is not a list of universally accepted "truths." Because psychologists are known for their tendency to disagree with one another, there are sure to be differences of opinion about this or any other similar list. Our intent, though, is to come as close as possible to a summary of the t concepts that all psychologists share. These are edu­as to the "true nature" of human beings as seen from perspective of the science of psychology. It is designed to organize your thinking about this course rather than to give you facts to memorize. Because it forms the foundation for the rest of the ever, it is an important section that should be read care­ughtabout.

• Human beings are biological creatures. We take our biological natu­re so much for granted that we often do not realize :nuch it influences our behavior. We experience emotional highs and lows because of the way part of our nervous is constructed. We spend much of our time preparing and eating food to satisfy the needs of our cells for energy. though our biology determines our behavior to a great - the limits it places on us are elastic; that is, we can them. The muscles given to us by heredity can be ;thened through exercise. Our native intelligence can be ed by a stimulating home environment. We can build es to fly and aqualungs for breathing underwater to me physical limitations. Although creatures of our bio­nature, we are not rigidly programmed by it. 
• Every person is different, yet much the same. Every human be­rruly unique. With the exception of identical twins, each person's heredity is unique, even compared with that of one's own family members. And each person's experiences are dif­ferent from anyone else's. It's inevitable that we should differ from one another in significant ways, and perhaps almost as in­evitable that psychologists would devote much of their time to studying the ways in which our personalities, intellects, and in­terests differ. Differences are a normal part of life that greatly interest psychologists. 

Yet as members of the human race, we are similar in our capacities to think, feel, remember, and so on. Thus, it's possi­ble to have a single science of human psychology. If we were not alike in human qualities, we would have to develop a dif­ferent psychology for each person. Fortunately, we are enough alike to be understood using one science of psychology, yet we are different enough to be interesting.

• People can be understoodfully only in the context of their cul­ture, ethnic identity, and gender identity. We are shaped by our learning experiences with other members of our culture. Our beliefs about right and wrong, our food preferences, our lan­guage, our religious beliefs, and many other facets of our lives come from cultural learning experiences. Among the most im­portant things that we learn from others is our understanding of what it means to be male or female and a member of our own ethnic group. It is impossible to understand a person fully with­out understanding the sociocultural forces (such as culture, eth­nicity, and gender) that influence them. 
• Human lives are a continuous process of change. From birth to death, humans are changing, developing organisms. We grow from helpless infancy through the time of playing with toys, through the time of adult work and rearing children, to the age of retirement. Change is almost continuous; standing still is rare in human lives. Much of this developmental change is in­evitably the result of our biological nature: Unless the process is disturbed, all creatures must grow from infancy to old age. Other aspects of change come from our experiences in life. Every time we learn a new concept from a college course, make a new friend, or adjust to a tragedy in our lives, we change in some way. 

These changes are usually so gradual that they slip by un­noticed. But the next time you ask yourself the question "Who am I?" remember that the answer you give today will be differ­ent from the answer you will give tomorrow. This is not to say that nothing stays constant in our personalities over time. ­I feel as strongly about prejudice as an adult as I did as a teenager-but change is an enormously important aspect of hu­man life.

• Behavior is motivated. Human behavior is not aimless. Rather, most of our actions can be viewed as attempts to meet our needs. We work to earn money for food, shelter, and clothing. We go on dates for companionship and perhaps to satisfy our sexual needs. We tell a joke at a party because of the sweet feel­ing of approval that laughter brings. However, not all of our motives are simple and selfish. Some of us are willing to spend long hours tutoring children with physical chall'enges just to see the joy of accomplishment in the children's faces. Others are internally motivated to express themselves in a painting or poem. 

Most basic motives (such as for food, warmth, compan­ionship, sex) are shared by all people and seem to be part of our biological makeup. Other motives vary among cultures and seem to be learned from others. For example, in some cul­tures most people want to be rich, famous, and important, whereas in other cultures most people try to avoid anything that will make them stand out from others in the community. Regardless of their origins, motives are important forces that guide our lives.

• Behavior has multiple causes. The question "Why did I do that?" rarely has a single answer. Behavior can be influenced by many factors, and it is usually influenced by many of them at once. Think about the factors that went into your decision to go to the restaurant up the street for something to eat at 10:30 P.M. last night. You went because you were hungry; you had finished studying; you wanted to have some companionship; you had just heard the place advertised on the radio; you re­membered the good time you had there last week; and so on. Behavior is influenced simultaneously by many "causes." 
• Humans are social animals. Like hives of bees and flocks of geese, people gather in social groups. The progress of modern civilization, and indeed the very survival of the human species, has been possible only because people work together in groups for the mutual benefit of all. From hunting large an­imals in the jungle to operating an assembly line, social groups are able to accomplish things that single individuals cannot. 

The social nature of human lives extends beyond mutual benefit, however. People need to have contact and relation­ships with one another. Imprisonment in solitary confinement is a harsh punishment because it deprives a person of human interactions. People seek out social support, friendships, and romantic relationships. When deprived of these social rela­tionships for even short periods of time, we know the pain that loneliness brings. Social relationships are a significant part of our lives.

• People play an active part in creating their experiences. Aristotle compared the mind of an infant to a blank clay tablet on which experiences leave their mark. In his view, we passively let experiences teach us about the world and be­come the person that they lead us to become. This is one of the few ideas of Aristotle that almost all contemporary psy­chologists have rejected. It seems to us today that people play a more active role in creating their experiences. The phi phe­nomenon discussed earlier was used by Gestalt psychologists to make this point: Often what we see-motion, in this case-is not in the outside world at all; the human nervous system creates it. 

At a different level, it's clear that people play an active role in determining what kinds of experiences they will have by seeking out particular kinds of situations. Some people regu­larly choose relaxed, low-pressure situations; others get them­selves into frenetic, exciting circumstances. We are shaped by these experiences. to be sure, but we playa role in choosing the experiences to which we will be exposed. We are active partic­ipants in the flow of life, not passive, blank tablets.

• Behavior can be adaptive or maladaptive. Humans have an amazing ability to adapt to the demands of life. We are flexi­ble. capable creatures who generally use our wits to adjust to whatever life dishes out in the way of challenges or pressures. Sometimes, however, we deal with life in ways that are harm­ful to us or to others. For example, some of us are excessively aggressive or much too timid, whereas others use a clinging dependency to get their way. These maladaptive ways of living can result from a combination of biological influences, ex­cessive stress, or improper learning experiences. They are cor­rectable, however, under the right conditions-such as good advice from friends, a change in life circumstances that encourages more adaptive ways to behave, or professional help. 

These ideas serve as starting places for our study of psychology. As you read the following chapters, you may find it useful to glance back to these ideas to see how what you are studying relates to them.