We can explain the popularity of 7 as a favourite number by looking at a classic psychology experiment. When asked to think of a random number between 1 and 10, most people will think of 7. Our response is determined by arithmetic. The numbers 1 and 10 don’t feel random enough, neither does 2, nor the other even numbers, nor 5, which is right in the middle … So we quickly eliminate all the numbers, leaving us with 7, since 7 is the only number that cannot be divided or multiplied within the first 10. Seven “feels” more random. It feels different from the others, more special, because – arithmetically speaking – it is.
We learn at school that numbers are tools for counting, but our relationship with numbers is quite clearly a deep and complex one, dependent on many cultural and psychological factors.
In the far east, superstitions about numbers are more noticeable than in the west. For example, 4 is unlucky for speakers of Mandarin, Cantonese, Japanese and Korean because the word for “4” sounds the same as that for death. Brands avoid product lines with a 4 in them, hotels don’t have fourth floors and aircraft don’t have fourth rows. (This is more disruptive than western fear of 13, primarily since, being smaller, 4 occurs more often than 13).
Eight is a lucky number in east Asia, however, because it sounds like the word for prosperity. A study of newspaper adverts in China, Taiwan and Hong Kong showed that 8 is by far the most popular non-zero digit in a price (for example in ¥6,800, ¥280). If you put an 8 in your price you make the product seem much more alluring.
These superstitions are not lightly held. Indeed, the association of 4 with death has become a self-fulfilling prophecy. US health records show that, for Chinese and Japanese Americans, the chance of suffering a fatal heart attack is 7% higher on the 4th of the month than would be expected.
East Asians hold deep superstitions about numbers, yet outperform western nations in the international league tables of mathematical performance, which suggests that strong mystical beliefs about numbers are not an impediment to learning arithmetic skills.