I remember the first time I spent the night at a friend’s house when I was growing up near St. Louis. I had a lot in common with this friend, so I was especially surprised when I discovered how different things were over at his house.

I was 10 years old. First of all, his house smelled different. I don’t know if it was the cooking, cleaning supplies or inhabitants, but the actual physical ambiance was noticeably different — not necessarily better or worse, just different.

It was Friday night and for dinner they served a lumpy fishy substance they called “salmon croquettes.” I forced down as much of it as I deemed necessary to appear polite, but in my house we were as likely to have fricasseed camel hump as these “salmon croquettes” things.

Even their dinner conversation was quite different from what I was use to, both in terms of politics and volume. This was perhaps my first realization about how different other people could be. I guess I had always thought that everyone else was just like us.

Working in mental health, my family and I have moved from state to state. I had many adjustment to make when I moved to Mississippi from Illinois, the Land of Lincoln. Florida had other customs and assumptions, and then moving to Indiana seemed like entering Bizzaro world.

After Illinois, Indiana seemed the same but different. We went to the same kind of church, but the times for Sunday school and the church service were reversed. Covered-dish dinners we called now called pitch-ins and “yards sales” were suddenly “tag sales.”

Back in the early 1950s, two of the leading social scientists of the day, Henry Murray and Clyde Kluckhohn, observed three quite obvious things about human nature that transformed the field of psychology.

Specifically, they noted that: 1. In some ways people are all alike; 2. In other ways they fall into groups that share characteristics with each other; and finally 3. In many very important ways people are completely unique. These observations helped launch the field of psychology known as “individual differences.” This is the area that studies such things as personality, intelligence, attitudes and values.

Although intellectually, we are aware of these differences among people, our biggest and most immediate frame of reference is always our own experiences. Since we use ourselves as the baseline, we tend to project our own perceptions, opinions and emotions onto another people. We easily come to believe that other people are like us. Psychologists call this the “false consensus bias.”

In the 1970s, Stanford psychologist Lee Ross conducted a study in which people were instructed to read stores about interpersonal conflicts. Each story had two very different possible solutions.

The study participants were then asked to guess which solution most other people would choose. They were also asked to reveal the solution they would choose themselves, and to describe what kind of person would choose each of the different solutions.

Results showed that participants uniformly thought that most other people would choose the same solution that they did, regardless of which solution they picked. The subjects consistently believed that other people thought the same way as they did, when actually they often did not. Participants tended to described people who didn’t make the same choice as having something wrong with them.

In a follow-up study, Ross requested that his subjects engaged in a mildly embarrassing activity — such as wearing an advertising sign around campus. Subjects were free to accept or refuse this task, without any negative consequences.

Of those subjects who agreed to the task, about two-thirds of them thought others also would agree. Of those subjects who refused, about two-thirds thought that others would also refuse the task. Subjects also characterized people who made different choices as cowards, show-offs or “just plan weird.”

Some psychologists speculate that we may overestimate how much others share our own attitudes and beliefs, because we spend a majority of our time with people who are much like us. People tend to select business associates, friends and partners who have similar characteristics and beliefs. Operating in a world of self-selected consensus may help us feel like we belong, but it also can lead us to believe that everyone thinks like us.

The false consensus bias also explains the “honeymoon effect.” We often go into new relationships, inaccurately assuming that the other person shares our beliefs and values. Over time, we may learn just how different they actually are and start negatively evaluating these differences.

Knowing too much about another person may be a problem. The famous baseball manager Casey Stengel once suggested that is a not a good idea to let people you work with have too much contact with people who already know you. He said, “The secret of successful managing is to keep the five guys who hate you away from the four guys who haven’t made up their minds.”

Relationship coaches Pace and Kyeli Smith recently published a self-help book on the “false consensus bias” entitled, “The Usual Error: Why We Don’t Understand Each Other and 34 Ways to Make It Better.”

The Smiths call assuming that other people are just like you the “usual error,” because it’s such a “common mistake and pitfall in communication.” The Smiths even believe that the traditional Golden Rule can get us into trouble. They have proposed an updated version, called the Platinum Rule. Instead of doing unto to others as you would have them do unto you, it states, “Do unto others as they would have you do unto them.”

The need to address false consensus bias in counseling has lead to a push to train therapists to be “cultural competent,” so that they can recognize cultural differences in patients. The failure to take in account cultural factors can be a major barrier to success. This is true not only in counseling, but also in business, education and especially international relations, as our nation’s experiences in the Middle East have amply demonstrated.

My wife, Diane, felt that her provincial outlook was blasted apart when she visited Great Britain and sat next to a woman from Australia, stayed at a sheep farm bed and breakfast, ate damson plum pie in pubs and ran around London. On the other hand, she was surprised that the weird Brits knew about pampas grass and rhubarb, which she felt belonged to America.

Our oldest son had an opportunity to learn about cultural differences when in college he developed a close relationship with a guy from Norway. I remember how his Norwegian friend was squeamish about eating the traditional American Thanksgiving dinner, and yet these are people who eat raw herring and whitefish soaked in lye.

If being aware of group differences is difficult, recognizing and respecting individual differences may be even more challenging. Our core beliefs, attitudes and behaviors are the essence of our identity. Thus, we are motivated to believe that our approach to things are not only socially accepted, but that they are also essentially “right.” Other people’s different beliefs may threaten and even anger us, since they imply that we are somehow “wrong.”

To truly overcome false consensus bias, first we must learn to recognize how much other people really differ from us and not commit the “usual error.” Ultimately, it’s important to be able to maintain our own beliefs, without feeling a need to obliterate the contrary beliefs of others.

Terry L. Stawar, Ed.D., lives in Georgetown and is the CEO of LifeSpring the local community mental health center in Jeffersonville. He can be reached at tstawar@lifespr.com or 812-206-1234. Checkout his Welcome to Planet-Terry blog and podcast at http://planetterry.wordpress.com.