I’ve made my share of mistakes predicting the behavior of others. I am not alone. Political commentators and stock brokers are poor prognosticators, despite their cocky self-assurance. Still, you’d think an intelligent person might be able to anticipate the behavior of those around him — friends and co-workers of regular acquaintance.

Here are some reasons why few of us are good at this:

1. The mistake of believing we think the same way. We have much in common with other humans, but not everything. Look around you at the superficial differences: bodies high as the sky or wide as a block; hairy and hairless; and all the hues of the rainbow if you include the artificial colors on top. Just as exteriors are unalike from person to person, so are the interiors. Your way of thought, perception, and motivation may be at odds with the person whose fortune you wish to tell. Don’t expect him to do what you might do.
2. Situations vs. traits. Many folks are “nice” in the daily course of life. They pet dogs, smile at children, and make charitable donations. Under pressure, however, some apply vanishing cream to their virtue. I’ve observed people I thought I knew turn monstrous — like a wolfman at the full moon: lying, breaking promises, and embezzling. I am not talking about patients. These individuals rationalized their misbehavior using doctrines of fairness drawn from the “Bizarro World” and considered unscrupulous “means” permissible because of high-minded “ends.” MORAL: you don’t know for sure who you are dealing with until your counterpart has been tested by temptation or fear; rage, humiliation, or misfortune. The Stoic philosophers remind us to test ourselves. Only in this way, they believe, can we recognize ourselves as we are, let alone grasp the workings of anyone else. Indeed, they argue that self-improvement should be the goal of any good life.
3. Expecting too much or too little. Some of us see the best in others, some expect only the worst. If your default prediction doesn’t match the behavioral tilt of the man whose actions you are trying to anticipate, you will be wrong.
4. Simple explanations. The world is a complex place. Bolts within wrenches within hands. Existence is too convoluted to comprehend all the factors that might make it intelligible. We simplify life by using shortcuts and broad, pithy descriptions of one another: “He is cruel” or “He is greedy” or “He is hard-working,” for example. A more refined evaluation, however, would reveal a hard-working man at one job, uninvolved in another. Our labels are misapplied — too black or white. We are tempted to demonize too many. Equally, leave the halos for the angels, not your fellow-man.
5. Absent historical data. Are you aware of the detailed life history of close friends? Even with knowledge of their every possible trauma and trouble, prediction is difficult.
6. Absent current data. Perhaps your buddy is experiencing medication side-effects or coming off his antidepressants. Maybe his mother or spouse is dying. Changes like these can cause him to be a new man, not the man you know.
7. Unresolved issues. A teen was a hell-raiser: she cut classes, ran away from home, shop-lifted  and had a too-early initiation into the world of sex. There were plenty of unfortunate explanations for this, but two decades on she appeared past “acting out” her troubles. Only she wasn’t. If you crossed her, she resumed the shape of the human wrecking ball she’d been at age 16. No one predicted it.
8. Expecting logic to prevail. We are told not to converse about politics or religion. That is, not encourage our conversation partner to switch candidates, adopt a new religion, or give up faith altogether. Jonathan Haidt and other psychologists note that Homo sapiens tend to arrive at emotionally driven decisions about highly charged issues and only then think of reasons to support them. A failure to factor emotions into your estimation of future conduct reduces predictive success. We all have witnessed behavioral train wrecks when powerful emotions take charge of the flesh and blood locomotive.
9. Self-destruction. Some folks burn down the barn to kill the rats. At the extreme, you find this in the Euripides play, Medea (she murdered her children because of betrayal by her husband, Jason) and in horrific murder-suicide news stories. Don’t expect future negative consequences to be considered in advance by everyone; and, even if noticed, to cause a course change.
10. Actions and reactions. Life provides moving targets, rather like a computer game. A good chess player “sees” several moves ahead. A wise person also adjusts his next step in response to the after effects of his last. It is almost impossible to know what another will do unless you understand all the things he will meet down the road, including his reaction to anything you do.
11. Poor affective (emotional) forecasting. Daniel Gilbert and colleagues looked at how happiness might be affected by work disappointment. They studied assistant professors at the University of Texas at Austin who either succeeded in getting tenure (the guarantee of a permanent job) or failed to achieve this goal (which usually means leaving for a different college or another line of work). Measures of happiness taken over a 10-year period indicated “the outcome of the tenure decision did not have a dramatic and robust influence on (the) general happiness (of the teachers).” The researchers concluded that we commonly ignore our emotional resilience and durability when imagining our future reaction to life’s disappointments. Put differently, we are lousy at forecasting our future emotional state. The divorce rate supports the same conclusion; as does the common, but erroneous, expectation of a wonderful life following a giant lottery award.

Without the ability to predict matters in our own lives, should we expect to read the tea leaves of others?

In summary, the next time you are about to take out your crystal ball, overconfident about your knowledge of the human condition, remind yourself of the following quote of H.L. Mencken. He was a scribe well-known for cutting us down in size:

No one in this world, so far as I know — and I have researched the records for years, and employed agents to help me — has ever lost money by underestimating the intelligence of the great masses of the plain people. Nor has anyone ever lost public office thereby.

A little humility is a good thing to keep in your back pocket for those times when the cigar of hubris explodes in your face. I need all the humility I can get, otherwise I’d offer you some.

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The top image is a 1910 poster of Alexander, Crystal Seer uploaded to English Wikipedia by Ali. The undated photo of the man with the cigar is H.L. Mencken.