How to Predict Human Behavior More Effectively

Nita Jain

Have you ever found yourself surprised by someone’s behavior? Perhaps a friend who had always shown you kindness betrayed you by disclosing private information. Maybe old classmates at a high school reunion felt unrecognizable from when you last saw them. Maybe you surprised yourself when you acted in a manner that was out of character.

Don’t Judge a Book by Its Cover

We often make assumptions about other people, but human judgment is extremely prone to fundamental attribution error, the tendency to ascribe traits to individuals based on behaviors we observe.

If someone donates to a food bank, we may assume that person is generous. If someone with a stutter has trouble expressing themselves during a job interview, we might erroneously assume that person is incompetent in other areas. Conversely, excellence in one discipline is not always transferable.

Folklore suggests that human behavior should be relatively easy to predict. Norwegian philosopher Jon Elster writes in his book Explaining Social Behavior:

People are often assumed to have personality traits (introvert, timid, etc.) as well as virtues (honesty, courage, etc.) or vices (the seven deadly sins, etc.). In folk psychology, these features are assumed to be stable over time and across situations. Proverbs in all languages testify to this assumption….If folk psychology is right, predicting and explaining behavior should be easy.

This assumption of stable character traits also underlies the aphorism, “Once a cheater, always a cheater.” But singular actions cannot be used to determine character. Personality is an evolving, fluid entity, not a concrete constant. If we develop expectations of people based solely on what we observe, we are working with limited information and setting ourselves up for disappointment.

Turn, Turn, Turn

If past behavior isn’t a good predictor, then what is? Freakonomics by Stephen J. Dubner and Steven Levitt might provide a possible answer. The central tenet of the book is that if you understand someone’s incentives, you can predict their behavior.

We can see this playing out on the world stage. Why would a large democracy like India refuse to take a stand against the atrocities committed in Ukraine? For the very same reason that China is maintaining its diplomacy.
Christian Lue on Unsplash

India’s allegiance with Russia stems back to the 1950s when the Soviet Union supported Indian sovereignty over the disputed territory of Kashmir. China’s leader seeks a future in which Taiwan is reunited with the motherland and would expect Russia’s support should that goal be accomplished by means of military invasion. Neither country wants to anger an ally, so both are maintaining silence out of convenience.

The same principle of incentivization applies to individuals, as personality traits are highly context-dependent. Your personality around your boss on a Monday morning is likely different than your behavior on a Friday night spent with your close friends. Elster explains, “Behavior is often no more stable than the situations that shape it.”

He describes a social psychology experiment in which theology students were asked to prepare for a brief presentation in a nearby building. Half the group was told to discuss the Good Samaritan parable while the other half was assigned a neutral topic. Each group was further subdivided into two more where half believed they were late and half were told they had plenty of time.

On their way to the other building, subjects came upon a man in apparent distress. Among students who believed they were late, only 10 percent offered assistance, but in the other group, 63 percent tried to help. In other words, preparing a talk about the Good Samaritan did not make students more likely to behave like one.

All the students involved in the experiment considered themselves good people, but the desire to avoid the judgment of a crowd seemed to override goodwill instincts. We need to understand character as the result of specific interactions between people and situations. We should pay attention to the interplay between the situation, incentives, and the person instead of ascribing broad character traits.

Let me share a personal example. The Myers–Briggs Type Indicator discriminates between judging and perceiving personalities. As a scientist, I frequently evaluate the quality of evidence by making judgments about reproducibility, methods, and study design. But around people, I tend to adopt the role of a wallflower or “transparent eyeball” (to borrow from Emerson), inconspicuously making observations devoid of any attempt to parse the data or draw conclusions.

Clément Falize on Unsplash

While personality certainly changes with situations, it also changes considerably across your lifespan. The longest-running personality study of all time, published in 2016 in the journal Psychology and Aging, found that personality undergoes profound transformations between the ages of 14 and 77.

The study began in 1950 with the recruitment of 1200 teenagers in Scotland, and teachers were asked to fill out surveys to assess their students on six distinct personality traits: self-confidence, perseverance, conscientiousness, emotional stability, originality, and desire to excel.

Researchers then reduced these six characteristics into a single dimension, which they termed dependability. Six decades later, the participants evaluated themselves using the same personality inventory and also nominated a close friend or family member to do the same. Researchers found no significant stability of any of the measured characteristics over the 63-year period.

Several confounding variables limit the utility of this study. The people answering the questions differed between the two time points. Teachers tasked with evaluating their students may have been prone to fundamental attribution error, and individuals asked to evaluate themselves were likely subject to the reference-group effect, the tendency to measure ourselves against our peers.

An outgoing introvert who is more sociable than his other introverted friends might describe himself as an extrovert, but his judgment is relative to his circle rather than an objective measure. While the 2016 study had several limitations, one noteworthy trend emerges across studies: “The longer the interval between two assessments of personality, the weaker the relationship between the two tends to be.”

The idea that you can become a completely different person over the course of your life could be comforting or frightening depending on your perspective. But maybe we’re missing the point. Attempts to assign personality traits are restrictive in some ways. We’re all a lot of things, walking contradictions, messy, imperfect, beautiful amalgamations. Maybe Sara Bareilles captured it best in her song from the musical Waitress:

She’s imperfect but she tries
She is good but she lies
She is hard on herself
She is broken and won’t ask for help
She is messy but she’s kind
She is lonely most of the time
She is all of this mixed up
And baked in a beautiful pie
She is gone but she used to be mine

Thanks for reading! 👋

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I am an independent researcher and freelance science writer. Topics that I find particularly compelling include the gut microbiome, women’s health, aging, longevity, and chronic diseases. As a writer, I focus on creating compelling narratives and providing value to my readers. As an editor, my responsibilities include fact-checking, formatting, removing extraneous information, ensuring proper transitions between sections, checking for proper grammar and spelling, and helping to craft an arc for the story. I have worked in both academic and clinical research settings. At the University of Georgia, I studied biochemistry and worked in a cancer laboratory as a research assistant. I am presently serving on the community advisory board for the ACTIV-4c Post-Hospital Thrombosis Prevention Study, a clinical trial conducted by researchers and medical doctors at Duke University as part of Operation Warp Speed.

Duluth, GA

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