Dan Gilbert, of TED talk fame, has an interesting article in the New York Times about magic numbers. The basic idea is that there are true magic numbers in math like pi, the Fibonacci sequence etc., but we also have magic numbers that we fixate on because of our physiology or because of something somebody decided arbitrarily thousands of years ago.

He began this journey into magic number when a doctor prescribed him a course of antibiotics for seven days. With a little research, he discovered that there is no actual evidence for how long is the ideal length to take antibiotics for is, but a week just sounds good. But a week is a length of time chosen by the Roman Emperor Constantine in the 4th century AD and I can say with certainty that he wasn’t thinking about antibiotics when he did it.

He discovers we have an unhealthy obsession with the number 10:

…a stock that closed the previous day at $10.01 will perform about as well as a stock that closed at $10.03, but it will significantly outperform a stock that closed at $9.99. If stocks close two pennies apart, then why does it matter which pennies they are? Because for animals that go from thumb to pinkie in four easy steps, 10 is a magic number, and we just can’t help but use it as a magic marker — as a reference point that $10.01 exceeds and $9.99 does not.

And that even the sounds numbers make can sway us:

In a recent study, one group was shown an ad for an ice-cream scoop that was priced at $7.66, while another was shown an ad for a $7.22 scoop. The lower price is the better deal, of course, but the higher price (with its silky s’s) makes a smaller sound than the lower price (with its rattling t’s).

And because small sounds usually name small things, shoppers who were offered the scoop at the higher but whispery price of $7.66 were more likely to buy it than those offered the noisier price of $7.22 — but only if they’d been asked to say the price aloud.

Anyway, it’s a neat, short, easy-to-read article, check it out. And here’s one of Gilbert’s TED Talks: