I can’t remember how I discovered lateral thinking puzzles but I do remember why I became fascinated with them – often the puzzles revealed an underlying assumption that was made without us knowing about it which, when actually challenged, would reveal the solution to the puzzle.

Here’s an example problem – see if you can get to the answer (typically, the person posing the lateral thinking puzzle would know the answer and the responder can ask as many yes or no questions as possible).

A man buys three bananas for a dollar. He then turns around and sells five bananas for a dollar. In this process, he becomes a millionaire. How?

I have asked this question to a lot of friends and co-workers who ask if there’s something funny about the bananas, is it the same dollar (currency) that he is buying and selling for, maybe he’s actually using the bananas to do something in between which results in additional profits, etc. I’ll reveal the answer at the end of this post.

As I was browsing a used book sale, I saw a number of books by Edward de Bono – having recognized his name as the authority in lateral thinking, I immediately grabbed these treasures of books. His book on lateral thinking may be one of the best books I have read to help generate new ideas – and as James Altucher says, ideas are the currency of the 21st century. Here is what I learned about lateral thinking:

Lateral thinking vs. vertical thinking

Vertical thinking is defined as A leads to B, which leads to C and D. It is typically one of the first ways of thinking that we are introduced to when we first learn about how to reason. Vertical thinking, as the name implies, involves stacking information using a pattern or structure that we have learned or previously used.

Lateral thinking is a method of arranging information in which we do not stack information but instead, move laterally (sideways) from A to E or to Q and back to D and then to K.

There are some great benefits to lateral thinking: it involves challenging assumptions, it can help disrupt patterns that you normally follow, it can help generate brand new ideas and it can help you see alternative paths that might lead to the same or better results.

Lateral thinking is primarily concerned with changing patterns

Edward de Bono helps to solidify a lot of the takeaways of the book through the use of examples. For example, there’s a story about a bird that tries to desperately drink out of a bucket, except that the water level is too low for the bird’s beak to reach. One way to approach the problem would be to use a straw to suck up the water. Another approach, which the bird uses, is to fill the bucket with stones or pebbles until the water level is high enough for the bird to drink.

In the first scenario, our ‘pattern’ of thinking is how to change the bird’s situation to get to the water. Reversing this pattern (a technique for lateral thinking) is how to get the water to the bird.

Techniques for lateral thinking

Perhaps the most useful section of the book is about the different techniques to facilitate lateral thinking. Each technique also comes with examples and practical tips on how to lead a classroom through each of the techniques. I do not cover all the techniques from the books, but those that I found most relevant and useful to my life.


Fractionation is the idea of breaking down a problem, design or function into each of its component parts and then examining each in detail. Edward uses the example of trying to get apples from a tree. This involves many different components including: going up to a tree, reaching for an apple, picking the apple from the tree, making sure that the apple is undamaged as it is being picked, transporting the apples, etc. Each of these can then be examined in different ways to look for different ideas / assumptions. For example, if you think about the idea of picking the apple from the tree, the tree is a certain height so whatever you are using to pick the apple also has to be able to reach the apple. But therein lies an assumption, why not plant the tree in a small trench so that as the tree grows, the apples are at an optimal height for picking?


A number of concepts, ideas and solutions may have a certain sequence or order in their steps. Or there is a certain way of thinking about the problem that involves ‘forward’ thinking. Reversal is the idea of going backwards.

For example, Edward points to a simple problem that we may all have faced as kids. The problem is that there are three fishermen who have tangled their lines (and the lines criss-cross on the page). Only one of the fishermen have caught a fish. Can you figure out which fishermen caught the fish?

One way of looking at the above problem is to try from each of the fishermen, follow the lines and to see which one leads to the fish. Doing this ‘forward’ approach may result in three attempts in the worst case scenario. Another way of looking at it is reversing the problem – from the fish, follow the line to the respective fishermen. In this way, you only use one attempt.

Here’s another problem: a tennis tournament organizer wants to know how many matches need to be played in a single knock out tournament of 111 players. How many matches need to be played to determine the winner?

Again, one way of thinking about the problem is to map it out using 2^n or A plays B and then A plays C scenarios. The reversal of this is to consider that there is only one winner and therefore, there must be 110 losers (and therefore, 110 matches) as each match creates one loser.

Entry point

Imagine that you are presented with two pictures. The first picture shows a man with a stick. The second picture shows a dog running. You might then think that this man is playing with his dog and the dog is chasing the stick. Now what if you are shown the two pictures again but in a different order. You first see a dog is running. Now you see a picture of a man with a stick. You might then think that this man is chasing this dog away from his garden.

The same information is presented in a different sequence and therefore, you think about these in a different way.

Here’s another scenario: suppose you want to draw yourself a bath. First, you put in hot water into the bathtub. Then you fill the bathtub with cold water until you reach the appropriate temperature for bathing. Doing it in this sequence means that you fill the bathroom with steam and condensation. In a different way, you can fill the bathtub with cold water. Then fill the bathtub with hot water until you reach the appropriate temperature for bathing. Doing it in this second sequence means that the bathroom is not filled with steam and condensation. It’s the same amount of water in both scenarios, but the sequence can lead to different results.

Or consider another example – many times, medicines or drugs are created or tested for specific purposes. Viagra was originally developed to treat hypertension. Erections were a side effect. However, viagra was later repurposes so that its intended purpose was to create an erection. Here, the entry point was changed to lead to a different result.


Analogies are incredibly useful – they can help to abstract complex information into something relatively easier to understand. Maybe you’ve heard of the analogy of a brain compared to a library. Or the analogy of a database being a magical genie that can retrieve anything you identify. Little did I know that analogies can be used to promote lateral thinking.

For example, say that you had the same problem of designing something to pick apples from a tree. One way to promote ideas and ‘movement’ is to create an analogy – say grabbing socks from a drawer. First you have to identify which drawer has socks. This is analogous to finding a tree with apples in them (and identifying if they are ripe, undamaged, etc.). Next, you have to get to the right height to open the drawer. This is similar to getting to the right height to pick the apples. In each of these analogies, you can explore the tangential relationships or similarities between the two scenarios. In this case, socks are very soft, so you do not need to be very strong to pick up and transport the socks. The socks are also quite durable so transporting the socks is not as big of a problem as apples. But is there a way to make the apples stronger? Or to make them more durable? Or softer so that it does not matter?

Random stimulation

One technique that I was really surprised about was the technique of randomly introducing something which could be related but in most cases, is completely unrelated to the idea. This could mean finding a random word in the dictionary. Or finding a book and reading a random article. Whether it is related or not is not important. What is interesting is that when the mind has two ideas, no matter how different, it always tries to find connections to link them together. Paired with the technique of analogies, this can help generate interesting and new ideas. Consider the idea of coffee and introduce a random word “noose”.

Noose -> hanging -> can we hang coffee beans to dry -> execution -> how do we create coffee -> trap -> can we trap the aroma of coffee and capture it in a way that adds value -> tightening -> does it matter that grinding coffee introduces air and how does that affect the taste

I made up this example but you can see that even things that seem completely unrelated can have some connection of ideas.

The use of a new word ‘PO’

One of the most interesting takeaways for me from the book is Edward’s introduction of a new vocab word: “PO”. PO is introduced, from my understanding, because “Yes” and “No” do not really capture the essence of lateral thinking. PO is a word for lateral thinking and it can mean several things:

*PO can mean let’s challenge the assumption that is being made
*PO can mean let’s not be judgmental or introduce judgment in any way
*PO can mean this step is a lateral step to a brand new idea – do not worry about how we got there but let’s think about the effect for now and run with it

Lateral thinking is an incredibly powerful method of thinking about problems or ideas in a different way. Here’s an interesting lateral thinking tip that I picked up – it’s better to fill your gas at night than during the day. Why? The next time you go to the gas pump, you may notice that there’s a small note that says that the gas is corrected to 15 celsius. If it’s colder, that means that you get a little bit more gas than when it is hot out.

Like these book notes? Every month I read on average 4 – 5 books, take notes and then summarize the key takeaways in a newsletter. Subscribe to Wang’s e-mail newsletter! and get immediate access to the top ten formative books that he has read culled from hundreds of the best non-fiction books and monthly book notes.