Even people who are officially “undecided” may have some leaning toward one candidate or another. Quite a bit of research suggests that the way that someone is leaning influences the way they interpret new information. If you have a slight preference for one candidate, then you are likely to give more weight to the positive things you hear about that candidate and the negative things you hear about the other candidate. In that way, you slowly start to confirm your initial impression.

The idea behind this effect is that we like to keep our beliefs consistent. That means that we tend to focus on information that supports what we already like and to pay less to information that might call our existing beliefs into question. This mechanism is also behind “ ” effects where people begin with a set of beliefs that are not consistent with each other and gradually change some of the beliefs until they fit together.

An interesting set of studies in the August, 2012 issue of Organizational Behavior and Human Decision Processes by Evan Polman and Jay Russo examined some seemingly small factors that can have a big impact on this kind of spreading coherence.

In their studies, they had people express a preference for two restaurants. The descriptions were designed so that if you saw all of the features of the restaurants at the same time, you would think they were quite similar and would have a hard time choosing between them. This was done by having four features that were about equally good for each restaurant and then one feature that strongly favored each restaurant.

The first feature people saw favored one restaurant over the other. One group was asked to circle which restaurant they thought was better at this point. Naturally, people tended to recognize that the restaurant with the better feature was currently the better option. After that, people saw additional features. After each one, people rated how much that new feature favored one of the restaurants over the other. They also rated how strongly they preferred one restaurant to the other up to that point.

Consistent with previous work, by the end of the study, 61 percent of people preferred the restaurant that had the best first feature. In addition, overall, their ratings of the other features favored the restaurant that they preferred at the start of the study.

But, that isn’t the interesting part.

Another group of participants expressed their initial preference in a slightly different way. Rather than circling the option they liked best, they had to use a pencil to completely darken a box to express their preference. This process took about 10 seconds. This extra effort increased people’s initial commitment to one of the options. For this group 75 percent of people preferred the option they liked initially at the end of the study. Their ratings of the other features favored the restaurant they preferred initially even more strongly than those of the people who just circled their preference at the start.

Why would having to darken a box increase people’s commitment to an option?

You might think that having to spend about 10 seconds filling in a box would give people more time to think about the first feature. However, in another study in this series, asking people to think more carefully about the first feature did not strengthen the effect of the initial preference as much as filling in a box.

Instead, it seems to come from the way people interpret the amount of effort they put into expressing this initial preference. Filling in this box take a lot of effort. People seem to attribute that effort to their commitment to the option.

The researchers explored this possibility in a third study. In this study, one group is told that filling in a box is an easy way to express their preference for one of the options. This group should be surprised that it takes so long to do it. A second group is told that filling in a box is a difficult way to express their preference. This group should not be at all surprised that it takes a while to fill in the box.

In this study, the people who think that filling in the box should be easy show a much stronger effect of their initial impression than the people who think that filling in the box should be difficult.

What does this all mean?

Our tendency to keep our beliefs consistent has an impact on the way we make choices. Over time, our initial beliefs affect the way we interpret new information so that those first impressions get stronger over time. Seemingly simple factors like the way that we express an initial preference can heighten this effect.

Perhaps the scariest part of these findings is that they typically happen without our awareness. That is, we think we are evaluating each new feature objectively when we see it. We do not usually realize how much our existing preferences are affecting the way we interpret new information. As a result, we think we have built up our eventual preference by evaluating lots of evidence independently, when in reality we have been influenced by our existing beliefs.

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