Do We Know Why We Act?

Looking back on our decisions, we generally feel as though we can explain them. Why did we hire that candidate instead of this one? Because he was clearly more qualified for the job. Why did we go on a date with that person and not the other one? Because he or she seemed nicer. Why did we sentence that criminal to a harsher sentence than this other one? Because she committed a more damaging crime. If we are making our decisions for rational, well thought out reasons, we should be able to explain to ourselves and others what those reasons are. And usually it’s pretty easy to come up with such explanations after our decisions are made.

It could be the case that we almost always act for good reasons, and that our explanations accurately reflect these reasons. But let’s consider an alternative hypotheses. Let’s suppose that much of our decision-making is influenced by factors that seem like they should be irrelevant, but that affect us below the level of conscious awareness. In that case, our attempts to explain our own behavior would often be incomplete. We would attribute our decision to X, when in fact Y and Z were also factors, perhaps as important as X. But, since we would be unaware of Y and Z, it might seem to us like our explanation X was complete.

So how could one test this hypothesis, that people are frequently influenced by factors which they don’t notice are altering their decisions? One approach is as follows. Randomly divide a population of people into two groups, A and B, of roughly equal size. Put everyone from both groups into nearly identical situations, with the only difference being that the experience of people in A differs in a single respect from the experience of those in group B. Choose this difference to be one that participants are unlikely to believe could have a significant chance of changing their behavior, but which you as a researcher think could in fact alter behavior in a specific way. Now see if the behavior of people in group A differs strongly in the predicted way from the behavior of those in B. If it does, this is evidence that we sometimes act for reasons that we don’t understand, and that our self reports of why we act may be inaccurate or incomplete.

Many studies of this basic format have been conducted, some with quite disturbing results. Consider the following scenarios:

  • An ordinary looking man comes up to you on the street and asks you for a dime. Take a moment to think of what factors would influence your decision as to whether to give him the money. Would you be influenced by how he is dressed? By whether he smiles? What behaviors could this person do to make it much more likely that you would comply?
  • A stranger asks you on a date, or asks you to dance at a club. Presumably your decision of whether to agree might depend on how good-looking you think the person is. But what other, subtler factors, might influence your decision?

It turns out that a powerfully influential factor in these cases is whether the person gives you a brief touch on the upper arm when making their request. As Richard Wiseman notes in his book 59 seconds, researchers have consistently found effects from physical contact. In one such study, a person asking for a dime was 20% more likely to get the money when they asked with a quick touch than without. In another study, 1.5 times more women accepted an offer to dance when a touch was used than when it wasn’t (with the acceptance rate jumping from 43% to 65%). A third study found that when attractive men asked out women on the street, their success rate doubled from 10% to 20% when they used a brief touch. People would never say “I decided to go out with him because he touched me on the arm”, and yet, it seems that about half of the women in the “touch group” of this latter study would in fact not have accepted the date without that momentary touch. Presumably, few if any of the women realized this.

Another fertile source of insight into decision-making is the book Yes!, on the tactics of persuasion. Consider these scenarios:

  • You are staying in a hotel and find a note that asks you to reuse your towels (as opposed to leaving them to be cleaned) in order to help protect the environment. You’d expect your level of devotion to environmental causes to influence whether you comply. But could it be the case that an alteration to the note could make your compliance much more likely? In one study, it was found that simply mentioning that the majority of people who stayed in your hotel room followed the request caused a 33% increase in people reusing towels. Yet, if these hotel guests were asked why they agreed to reuse their towels, it seems unlikely that many would say it was because other people did it too. We often subconsciously take cues from others which influence how we act.
  • You get a phone call one day from a group conducting a study for a “public service publication”, and they would like you to participate. The person on the phone says that participation will involve “five or six men from our staff coming into your home some morning for about 2 hours to enumerate and classify all the household products that you have.” What simple trick could this organization use to substantially increase the chance that you will say yes? It was found that when homeowners were called three days before this request in order to give them a phone interview about their product use for the same publication, they were 2.4 times more likely to agree to the later, much more invasive request. Those who didn’t receive an earlier call agreed to allow the surveying men to come 22% of the time, compared to 53% of those who did receive an advance call. And yet, it seems unlikely that those people whose behavior was altered by the non-invasive phone survey would be aware that it was an essential ingredient in their decision. Agreeing to do something small can unwittingly make us far more willing to do a similar but much larger thing later on.
  • You receive a survey in the mail, sent by a stranger, along with a typed request that you complete it. Presumably, if you find the survey topic interesting, you may be more likely to do so. But regardless of your interest level, what variable could the sender change to make you much more likely to fill it out? In one study it was found that if a handwritten sticky note was attached that requested the survey be completed, the chance that the survey was returned was more than doubled, from 36% to 75%. The slight increase in effort and personal touch of attaching a hand written sticky note made people substantially more likely to want to help out.

Do these sorts of effects only hold on unimportant choices? Let’s consider some decisions where money or lives are at stake.

  • You are interviewing college students for a job. Presumably you will take into account their quantity of work experience and grade point average. And yet, in one study, total months of work experience and grade point average did not have a statistically significant effect on whether candidates were offered a job. What did have a significant positive effect was whether the candidates tried to ingratiate themselves with the interviewer (e.g. by conforming to the interviewers opinions and offering favors). We naturally want to hire people that we feel positively towards, even when we believe ourselves to be evaluating them on objective criteria.
  • You want to buy a subscription to the economist. You can choose the web only version for $59, or for $125 get the print version which also includes web access. Which would you select, and why? Surely after the fact you would be able to explain why one would be more right for you than the other. But as Dan Ariely discusses in his book Predictably Irrational, when he conducted a study on this scenario he found that adding a third subscription option which nobody selected massively altered people’s behavior. If a $125 print only version is included as an option, which is similar to the $125 print-and-web option but strictly worse, the preferences of subjects switched from 32% favoring the print-and-web version to a whopping 84% preferring it. The latter group thought they were choosing for good reasons, but in fact many of them changed their minds due merely to the decoy option being offered. The decoy option was clearly worse than the print-and-web version, therefore making the latter look more compelling positive on a relative basis, even though no one wanted the decoy.
  • It is your job to determine how many years someone should go to jail for illegally entering her neighbors apartment and stealing money and merchandise. Your judgement will be based on a description of the crime, as well as a photo of the criminal and routine demographic information about her. What factors do you think will alter your decision of how long a sentence you’d apply? When such a study was conducted on undergraduate students, it was found that when the photograph of the criminal was switched from an attractive woman to a substantially less attractive woman, the average prison sentence that the students assigned increased by a factor of 1.9, from 2.8 years in jail to 5.2 years. The average sentence that the less attractive photo produced was about equal to that of a control that was identical except that it included no photograph. Beauty and ugliness can substantially distort our perceptions of other people, even with regard to traits that have nothing to do with a person’s looks.
  • You’re again given the task of determining the sentence that an accused criminal should receive based on details about their case. You’re also given the prosecutor’s sentencing demand, but you know this demand is random, because you determined it yourself by rolling a pair of dice and summing the values. Surely, the sentencing demand wouldn’t influence the sentence you would give. Right? In one such study, the sentences that lawyers gave in such a scenario were almost 1.5 times higher when their dice came up with high values than when the dice had low ones (the mean sentence rising from 5.3 months to 7.8 months). The values we assign to things can be substantially influenced by suggested “anchors”, even when we know intellectually that those anchors are irrelevant.
  • You’re filling out a form and have the option to sign up as an organ donor. One might imagine that your sense of obligation to other people might come into play. But could the way the form is written have a large impact on this weighty decision? In one study, when people were presented with opt-out organ donation forms (or ones where a choice was forced) people said they would be willing to donate their organs at twice as high a rate compared to if they were presented with an opt-in form. Furthermore, it was found that out of a sample of 11 countries, all 4 countries that use an opt-in organ donation procedure had organ donation rates lower than all 7 countries with opt-out procedures. Yet, it seems unlikely that many people attribute their organ donation choices to whether or not they had to check a box. Sometimes the default or “standard” choice, can have a powerful effect on what we decide.

These studies, and the many others like them, raise serious questions about the extent to which we understand why we make the choices that we do. Seemingly irrelevant or unimportant information seems to powerfully alter our behavior in a wide variety of circumstances. Those influences that are subconscious are particularly pernicious, because their very nature prevents us from noticing how they affect us.

So the next time you think you know why you made a decision, don’t be so sure that the story you tell after is the actual story.



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  1. Excellent post. I’m a firm believer that we backwards rationalize our reasons for almost everything, so it was really nice to read an article that confirmed my already held opinion. I’m sure that if it had said something else, I would have just ignored it however 🙂