Some choices are made when all of the options are right there in front of you. For example, if you go to the supermarket, you see the wall of tomato sauce, and you can stand in front of it and compare all of the different brands and the different flavors of sauce for each brand.
For other choices, though, you get information about the options one at a time, and then you have to make a decision. For example, if you are buying a new car, you have to go from one dealership to the next, test driving cars and talking to salespeople. Students who apply for graduate schools may visit the schools to which they have been accepted in a sequence until they have to make a decision about where to go.
What happens in those cases?
A paper by Antonia Mantonakis, Pauline Rodero, Isabelle Lesschaeve, and Reid Hastie in the November, 2009 issue of Psychological Science looks at this question. They had people sample a number of wines in a sequence. After sampling the wines, they had to decide which one they preferred. Participants were assigned to try 2, 3, 4, or 5 wines, and the sequence was determined randomly.
The choices people made depended both on the number of wines they sampled and their expertise about wines. For people who did not have much expertise, they were most likely to choose the first wine they sampled. For example, when there were two wines, people selected the first wine they tried 70% of the time. For a sequence of five wines, they still picked the first one 50% of the time (but if they had chosen a wine at random, they would only have chosen this wine 20% of the time).
For people who had more expertise, there was a combination of two effects on choice. There was still a tendency for experts to select the first wine they tried. When sampling only 2 wines, they picked the first one 80% of the time. When sampling 3 wines, they picked the first one about 65% of the time. But, when they sampled 5 wines, they picked the first one only about 25% of the time. In this case, they picked the last wine they tasted about 40% of the time.
Why is there a difference between experts and non-experts? The wine experts have a more sophisticated ability to taste differences among wines. So, they keep comparing each new wine they sample to their favorite. There is a tendency for the first wine to be a favorite, because it sets the standard for comparison. However, each new wine that is sampled will have some new flavors, and so they provide a reason to pick the last wine tasted. The experts taste these new flavors and so they tend to stick with the most recently tasted wines, particularly when they taste a long sequence of wines. The non-experts can't taste much difference among the wines, so they often stick with the first one they sample.
One thing that is interesting about these results is that the wines in the middle of the sequence are not chosen very often. There is an overwhelming tendency for people to pick either the first or the last of the items in the sequence. For example, for experts choosing from among 5 wines, the first and last items accounted for about 65% of their choices, while the remaining 3 items accounted for only about 35% of the choices.
What does this mean for you?
If you are in a situation in which you have to sample the items in a sequence, and if the choice is important to you (say a car or a graduate school), you should try to write down your criteria for making a choice in advance. Try to evaluate each option after seeing it by using these criteria. If you discover a new dimension for evaluating options after seeing the third or fourth item, go back and evaluate the earlier items along that dimension as well. Do what you can to give each of the options (even the ones in the middle of the sequence) the best chance to be the one that gets chosen.