Odd vs Even number Psychology

Photo by Nick Hillier on Unsplash

Classification of Things

The ability to classify objects is crucial to thinking. We place objects into categories which helps us predict it capabilities and features. For example you hear a bark outside your house and you instantly categorise the sound to be of a dog. You can now predict that it will be four-legged animal who might want to chase a ball or gnaw on a stick. In this way, the defined categories enable you to use your past experience and help in understanding new situations.

In case of numbers, we often categories then into prime, composite, binary, decimal etc.. but the most common of them, ODD and EVEN.

I was startled when a fellow colleague asked me “Why does MS Word have only even number font sizes predefined?” My first response was that, “even numbers look to be pleasing”. I knew this was in someway right, but it was only my opinion which had no facts to prove. And a UX designer relies on research, not baseless opinions. So, my study on Number Psychology began.

Public Polling

I did a quick read about the cognitive behind numbers and headed out straight to polling. I asked 185 different people (different countries, different culture, different religion) about their most liked number. It was a random question which startled people but, that was the whole point. I did not want them to give it a lot of thought and come up with an answer. Just think of all numbers between 1 to 10 and pick the one which pleases you the most.


49% liked then number 7

24% liked the number 3

19% liked the number 1

8% Others

While some of the choices were based on factors like Astrology, Birth date, Family number etc, most of the choices were personality based. And so, there was still a clear winner amongst all.


Number 7

It is interesting that our favourite number is 7, an odd number, when even numbers are more liked and seen as calmer and better than odd numbers. In fact, in my survey, favourite numbers are much more likely to be odd than even. 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.

From religious connections to being the ultimate “lucky” number, 7 is a number that we all seem to gravitate towards. Some of the numbers mentioned below are bound to cultural beliefs and superstitions, but seven safely seems to be a worldwide favourite. The number could be our favourite due to its constant presence in our world and religion. Here are just a few:

7 Deadly sins, 7 colors in the rainbow, 7 continents in the world

Religion: Seven days to create the earth, seven deadly sins, seven heavens.

Earth: Seven colours in the rainbow, seven continents, seven wonders of the world.

From a marketing perspective, the number 7 is a people pleaser that should be easy to implement. Examples: Jack Daniels Old No.7, 7-UP, 7 Stars.

The Odd Effect — an experiment

Terence Hines of Pace University in the US conducted another experiment that helps explain why we view odd and even numbers differently. He displayed pairs of digits on a screen. These would be both odd, like 1 and 3; both even, like 6 and 8; or one of each, like 1 and 6.


Participants were asked to press a button only when either both digits were even or both digits were odd.

On average it took respondents 20% longer to press the button when both digits were odd. He calls it the “odd effect” — it takes our brains longer to process odd numbers. They are literally more thought-provoking.

Art Gallery - Odd number showcases

At an art gallery, most of the times, we find then number of paintings on a wall to be odd numbered. This is because, even numbers bring symmetry and we tend to ignore them as they become a part of the ecosystem. But the moment, there are odd numbered structures on the wall, we loose the ability to group them automatically and thereby gaze at it for a while. This attracts attention.

To answer my colleagues question of even numbered font sizes in MS-Word or other applications,

  1. Even number makes you think less, it has less of attention seeking capability. While drafting a letter or writing a memo, font sizes are important but not the primary role. Hence, major focus need not be given to the font size. It is one of the most frequently traversed secondary journey which the user must get accustomed to. Hence the even number.
  2. Also, standard font sizes across devices/paper sizes are generally even numbered. So, helps in maintaining standards.


Even numbers feel more homely, friendly and must be used at all times when seeking attention is not the primary objective. Whenever we need focus on a subject and demand the users attention, try using odd sequence numbers.

References and Inspiration: