Comparing options makes you confident in your choice.
There are two broad strategies that people use to make choices. One method is to compare the options to each other and choose the best one. The other is to evaluate each option individually and then pick the one that is rated as the best.
These strategies are used in different circumstances. In his book, Sources of Power, Gary Klein suggests that experts are more likely to evaluate the options individually, while people with less expertise tend to compare the options.
One reason why comparison helps novices more than experts comes from research by Chris Hsee. This work shows that it is easier for people to evaluate the options when they are being compared. Imagine buying a new dictionary. You find out that a particular dictionary has 50,000 entries in it. Is that good or bad? If you are a dictionary expert, the you might know whether that is a large number of entries. Suppose, though, that you find out that another dictionary only has 25,000 entries in it. Now, you know that 50,000 entries is a good number for a dictionary to have.
To get participants in their studies in a mindset to make comparisons, they had people look at a complex picture and write down the commonalities and differences between two halves of the picture. Other participants evaluated the picture without making comparisons. Previous work by these researchers shows that this technique reliably gets people to make comparisons in later tasks.
In one study, after looking at the complex picture, participants were shown descriptions of three brands of cell phones (labeled Brands A, B, and C). They had a chance to study the descriptions. Later, they were shown fourteen of the features they had seen and were asked whether those features belonged to Brand B. With each response, participants were allowed to place a bet between 0 and 10 Euros (the study was done in Germany) based on how confident they were in their response. The higher the bet, the more confident that people were that they knew whether the feature belonged to Brand B.
People who were put in a mindset to make comparisons were more confident in their judgments about the features of the cell phones than people who did not make comparisons. Despite the difference in confidence, the people who made comparisons were not more accurate in their judgments than those who did not make comparisons.
This confidence can also affect the choices people make. In another study, participants were shown the menu from the university cafeteria before lunch. They were asked to select the item from the cafeteria they thought they would want to eat. As before, some participants were put in a mindset to make comparisons while others were not. After lunch, participants were asked what they actually ate. Those who made comparisons ate what they predicted they would eat about 75 percent of the time, while those who did not make comparisons at what they predicted they would eat about 50% of the time. (Because there were about 10 items on the menu, chance would be about 10%.)
Putting all this research together, it suggests that when you don't have a lot of expertise in a domain, you need to be careful when making decisions. On the one hand, you are quite likely to rely on comparing the options in order to make a choice. On the other hand, those comparisons will increase your feeling of confidence in the decision. So, you need to recognize that at least part of that confidence comes from the way the choice was made.