Book review: My Hidden Chimp

tl;dr: A narrowly framed introduction to dual process theory for ~5-10 years olds.

I love a dual process theory metaphor as much as the next rationalist (researching this post I came across King Louie and the Apes which I quite like). The Blue minimising robot series completely changed how I thought about myself and cleared up a lot of the confusions that I had about myself (e.g. what I would now call akrasia). I would say that, personally, dual process theory is the most useful thing that I have learnt under the umbrella of rationality.

I have frequently wondered how different my life would have been had I understood myself better at an early age. How would one go about explaining this to a 6 year old?

I have two children (6 and 4) and had tried to explain a bit about the 2 systems to them but with limited success. I particularly thought it would help my eldest as he can struggle behaviourally and experiences extreme emotions but he didn’t fully internalise what system 1 /​ system 2 meant. Then I heard that Prof Steve Peters had released a children’s book based on his chimp model and I was intrigued enough to get it for him as a Christmas present.

[note that there is a companion book to My Hidden Chimp called The Silent Guides which is aimed more at parents but which I haven’t read]

The Author

I’m not sure how well known Peters is outside the UK but over here he is a minor celebrity. For most people I suspect that if I mentioned Peters by name they wouldn’t know who I was talking about. If I said “You know, that sports psychiatrist who works with cyclists, the chimp guy” then they probably would.

He is probably most famous for his work with British cycling as part of their programme of incremental gains. Most recently was in the news for being credited by Victoria Pendleton for preventing her suicide.

He has also worked with Ronnie O’Sullivan which was where I first noticed his work. Prior to working with Peters, O’Sullivan struggled with drink, drugs and depression but in recent years has turned this around, giving Peters a lot of the credit.

He is also an age group world champion in 100, 200 and 400m.

I’m not his publicist, honest...

The Chimp Model

The chimp model is Peters’ dual process metaphor. Different writers and models seem to me to have subtly different focuses—e.g. Robin’s Elephant and rider focuses on motivation, Kahneman’s system 1 and system 2 on decision making. The chimp model in My Hidden Chimp focuses on fast, emotional responses.

An adult explanation of the chimp model is given in Peters’ previous book The Chimp Paradox. The Chimp model is expressed as the human (frontal lobe, a.k.a blue brain) and the chimp (limbic system, a.k.a red brain). My Hidden Chimp goes into less depth but explains how a chimp has a very small blue blue brain so it mainly decides things with its red brain, hence calling it your chimp. The human (blue brain, “You”) is the you that you really want to be.

[The Chimp Paradox (which I also haven’t read) goes into a triple process theory by adding the computer which stores and acts on memories. This isn’t mentioned in My Hidden Chimp, I presume because it is a simplified version for children.]

The Book


In the first third of the book, the chimp model is introduced, explained and made relevant with examples. The remainder of the book describes 10 habits which help us to manage our chimp and how to build the habits into our life.

Teaching methods

As you might expect from a children’s book, it is full of brightly coloured pictures.

The examples in the book are 4 children and their chimps in various different circumstances where the human thinks one thing and the chimp is thinking something else. For instance you want to go for a walk but your chimp wants to stay at home and do nothing or you know that you’re safe in bed but the chimp is scared of the dark. The examples given are wide ranging so that readers will recognise themselves in some of the characters. The chimps are given names (readers name their own chimp too) and are often presented humourously.

This is probably the best thing about the book. We had many moments of self-recognition as we read it, as did other people who I’ve heard talk about it.

In addition to the examples, there are exercises throughout the book, for instance listing times where you’ve acted in a way that you wish you hadn’t. These help with applying the lessons and to building commitment to act on the lessons.

Section 1 - Chimp model

The first section of the book gives a brief introduction to dual process theory and the chimp model in particular. It introduces the 4 characters and their chimps and gives examples of what they’re thinking.

The book tries to avoid some problems otential pitfalls, for instance explaining that your chimp is part of you so you can’t just blame it when you do something naughty. You have to make sure it behaves itself like you would with a pet.

Section 2 - Habits

The second section explains 10 habits which help manage your chimp. These are some of the basic building blocks that you’ve probably told your children about 100 times (learning to share, learning that no means no, saying sorry). Talking about them in the context of our hidden chimp works well to show why they find them hard to do but also why they are important.

Age range

The book doesn’t give a recommended age range but a lower bound would be the ability to understand and act on dual process theory when explained in an age relevant way. The upper bound would probably be not feeling patronised by the childish cartoon drawings. 5-10 is a fair guideline.

The book states that it can be read by the child on their own or with an adult. I would suggest that (for younger readers especially) the book should be read with an adult as I feel misunderstanding the content could have negative effects.

Potential Criticisms

Here I cover not only some of my own criticisms but also some criticisms which I expect other rationalists might have, even if I think the book deals fairly well with most of the issues.

Explanation of the chimp

I found the explanation of the chimp slightly confusing. The original explanation makes it sounds superficially as though it is the part of you which makes you do naughty things. This pivots to the part of you that is “acting without your permission”. This is slightly vague but the book makes up for this with repeated extensional definition, giving examples to indicate the kind of thing which it is talking about. Extensional definition seems like the right way to go about explaining it to a child so overall I think this works fairly well.

I should note that re-reading the book it is fairly clear what it means from the beginning yet somehow I (and others) found it confusing on first reading—go figure.

It’s important to mention that Peters’ chimp is not exactly analogous to my mental model of system 1 - my impression is that the chimp is a more narrow framing. The Chimp includes immediate, emotional, visible responses. It doesn’t include other opaque subconscious processes such as those which deal with long term motivation. It is possible that the Chimp Paradox deals with these other issues but the focus of MHC is firmly on short term emotional actions.

This probably makes sense as a children’s book as when we are young we tend to be more short term and react emotionally so learning to deal with these parts of our mind seems like the priority.

Identifying with system 2

This leads on to another potential problem. I suspect that some people might be unhappy with the book’s framing of your system 2 being the you that you really want to be and your system 1 being the part of you that acts without your permission. I’ve seen similar criticism of the Chimp Paradox.

Personally, I found that this worked well as a children’s book and would worry that a more nuanced framing would confuse matters. I intend to go into the rest of the story when my children are older, a bit like I’d teach a child Newtonian mechanics first and wait until they’re older to explain relativity.

I would understand if others took a different point of view (I’m not 100% convinced mysel) so I’ve just described it and will let you decide how happy you would be with the framing given.

The fact that the chimp is a more narrow framing than the elephant might help assuage some worries but I’m not sure. There is a concerted effort to describe how our chimps can sometimes be helpful – e.g. our chimp helps us to have fun and warns us of danger. The often-humourous presentation of the chimps also helps with appreciating the chimp.

However, the book also presents us as having to put our chimps in a box when they are misbehaving. The examples given in the book are of circumstances where the chimp is having a negative effect on our lives (not sharing, telling lies to parents, being unkind to friends). I’ll grant that there are edge cases where these actions might be beneficial but, especially for a child, the advice to prevent our chimps from doing these things overall seems like the right way to go.

Taking the metaphor literally

Dual process theory is a model of something much more complicated. We are not two people or a single person with a limbic system attached. Our brain is a big mass of neurons and connections of which we only understand a very general picture. Peters deals with this by stating carefully that this is just an interesting way to think of how our brains work and not reality. However, for most of the book he just writes as if the model is literally true. This can seem slightly odd but I suspect that it is better than the alternative of constantly qualifying every statement. I just ended up having to remind my son that it was a model every time I thought he might be taking it too literally.

Book not matching life

One particularly interesting experience was talking about the habit of sharing. Peters presents this as our human wanting to share and our chimp not wanting to share. My son pointed out that actually he and his chimp and were in agreement that they didn’t want to share. I don’t know how common this would be but I’d tend to agree with my son that my system 2 by default (especially when I was younger) doesn’t particularly want to share.

I suspect that there’s not much a book can do about this and that it’s a case of adding your own explanation to the book where it doesn’t exactly meet what the child needs. In this case, I reminded my son about “cooperate or defect?” (as we call Prisoners Dilemna) and how cooperating often means a better result in the end. This is part of the reason I’d recommend the book being read with an adult—customisation.


The main critical comments from online reviews seem to be:

Too young for my child (~12 is too old)

The 10 habits are things you’re teaching your child anyway—nothing original

Kindle version is poor

Did it work?


Obviously I have to add the usual caveats that it’s only a sample of 1, perhaps its regression towards the mean, maybe the other things I’ve been working on with my son have made a difference.

Even given that, I am confident that he has understood dual process theory as presented in the book and started to recognise when his chimp “takes over”. As a result, he is more able to e.g. stop himself when he gets angry or to override his instincts not to share. Reading it with him has also given us a common framework to talk about what went wrong when he has lost control.

Before reading the book I could often see how his mind was working when he did lose control and could tell that he was desperately searching for ways that he could still be in the right. Then afterwards you could see how confused he was with himself and he couldn’t figure out why he’d done what he did. Now he feels like he understands what went wrong and how he can do better next time.

He has avoided the obvious pitfall of just blaming his chimp and, if anything, is better at taking responsibility for his actions.

So throughout this review I have had to prevent myself from just saying “THIS BOOK IS AMAZING AND ANYONE WITH A 5-10 YEAR OLD CHILD SHOULD BUY IT IMMEDIATELY!”.

I realise that it is likely that it may not work quite as well with every child. The book could have been written with my son in mind so if it was going to work for anyone it was going to work for him.

You can make up your own mind if you think it will work for your family.

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