Whether you love them or hate them, numbers play an important role in your daily life. You need numbers to plan your day. Without numbers, you'd have a hard time figuring out what time to have meetings or lunch dates, which floors or streets to meet people at, or how many sales you hope to get by sunset. At the end of the day, you need numbers to record what you did whether it's how much you spent, ate, or scored on Angry Birds. Numbers also allow you to determine how much you can spend on the things that you want and whether there will be anything left in your bank account at the end of the month. Without numbers telling you what the temperature will be, you'd be unsure of whether or not to pack an extra layer when you leave home. You'd definitely find it difficult to cook a meal unless you're a top chef in the making or have a storehouse of family recipes at your disposal.
Many people claim to hate anything involving numbers including (and especially) math. Statistics is often a psych student's least favorite course. However much we protest our desire to avoid numbers, though, it turns out we are obsessed with them anyway. Unfortunately, some people can develop an obsession with numbers that goes beyond the norm; in some forms of obsessive-compulsive disorder, people have a counting compulsion that forces them to count everything in which they come in contact.
Number obsessions, in modified form, creep into our everyday lives without our even being aware of their existence. Consider how popular numbered lists are in the realm of practical advice. Whether it's how to plant the perfect herb garden or how to nail a job interview, a list makes us feel secure. David Letterman's Top Ten List is a cultural icon. Some may call this "brain porn." When we see a list, we know that the chaos of the universe will be transformed, if even for a moment, into an understandable set of steps.
Of all the numbers there are, 7 is the one that people seem to have the greatest attraction. Top ten lists asides, 7 stands alone as the most preferred number in people's minds. Let's see why.
1. 7 is magical. The religious and spiritual associations to the number 7 go back through the millennia, ranging from the 7 deadly sins to seventh heaven. The ancient world was declared to have 7 wonders in it although there were obviously countless others that deserved this designation.
2. 7 is lucky. The prototypical lucky number, 7 is a heavy hitter in the gambling world. Slot machines often offer three 7's as the big payout. Our brain feeds off positive associations, and "Lucky 7" gives us an automatic preference for the number itself.
The next three reasons relate to 7's quality as a number:
3. 7 is a good playoff number. You will never have a tie when there are seven events needed for a deciding outcome. When 5 doesn't seem like enough and 9 like too much, 7 is the perfect halfway point.
4. 7 occurs throughout nature. There are 7 seas, 7 continents, 7 colors in the rainbow, and 7 days of the week. The number 7 has interesting properties, including the fact that it's the total of all opposite sides of a single die.
5. 7 sounds good. As NPR commentator Frank Deford pointed out, 7 is the only single digit number that has two syllables. "Snow White and the Seven Dwarfs" rolls off the tongue. "Snow White and the Eight Dwarfs" just doesn't work quite so well.
The final 2 reasons involve our brains and the way we process information. We may literally be programmed to like the number 7 because our brain is hard-wired to clump things in 7's.
6. 7 is the size of a memory chunk. The psychologist George Miller observed many years ago that our short-term memory remembers in units of 7 plus or minus 2. You can remember an infinite list of words, tasks, or facts if you organize it into 5 to 9 (but ideally 7) chunks.
7. 7 is a neuron's favorite number. For years, scientists were mystified about the reasons for Miller's "magical number 7 (plus or minus 2)." Now we may know why. A 2008 study on neurons in the memory input unit of the brain, the hippocampus, showed that they produced the best information when their dendrites (the branches that receive stimulation) numbered 7. Perhaps we remember best in 7's because that's what our brains are best able to store.
You've read the 7 reasons. Let's think back on that concept of "brain porn." If our brains are hard-wired to remember in terms of 7's, then it would make sense that we prefer 7's for everything from world wonders to Seven Dwarfs. The number 7 feels right because we can easily process information that falls into this many units.
When we can remember more information, we also learn better. According to the theory of "cognitive load," learners need to minimize the amount of information they have to keep in consciousness ("working memory") until they gain familiarity and expertise. The principles of cognitive load theory apply to all sorts of instructional materials, from powerpoint presentations at sales meetings to schematic diagrams and to the way you talk to your friends and family. You need to present your information in as easily chunkable a form as possible or the learner's resources will be depleted.
As an aside, there are other interesting implications in daily life for cognitive load theory. For example, if you're presenting a graphical diagram, you should place the labels where they belong in the diagram, not in a legend on the side. A map should have place names where they belong on the map, especially for the geographically-challenged. The reader or learner only has to glance at the diagram or map instead of wasting precious mental energy on trying to connect words and pictures. Of course, all of this works best when you're giving people a chance to chunk.
Knowing that the brain prefers 7 to any other number (plus or minus two) can help you in important areas of your life. Reduce your own cognitive load to manageable chunks so that you can keep on top of the information you need to do your job. If you're trying to communicate to others, you'll get your point across more effectively if you reduce the cognitive load you place on your audience.
Now, what were those 7 reasons again?
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Copyright 2011 Susan Krauss Whitbourne, Ph.D.
Migliore, M., Novara, G., & Tegolo, D. (2008). Single neuron binding properties and the magical number 7. Hippocampus, 18, 1122-1130.