Eating habits II - Your Chimp Brain, Human Brain & The Famous Marshmallow Study

In part I of this article recall one of the differences between a human and a chimpanzee in a superstore was the superior brain of the human enabling us to have a decision making process chimps don't have, we have the ability to say 'no' to our instincts, to have will power and judgement.

This requires sophisticated processing in our brains that mean physiological outputs of the brain like vision, pain, thirst, and for purposes relevant to this topic - hunger can be heavily influenced and changed 1 .

It turns out, that there is a metaphorical 'chimp' and a 'human' brain in each of us and these parts of our brains serve very different purposes to keep us alive. Of course there is not literally a chimp in our brains (or a human) but it is a superb metaphor developed by Professor Steve Peters in his book 'The Chimp Paradox' to help us understand our decisions and choices. Please now watch the video below, a wonderful overview of this important concept 2 .

Go back and actually watch it!

This metaphor is important, if the brain was always rational in how it interprets a situation we would seldom need credit cards and very few people would overeat. We often make choices and pit ourselves against our future self with the evidence showing these choices being very often self destructive3.

Parental Instinct
— The Chimp Paradox, P.31

The following passage is taken directly from Stephan Guyenets (2017):

"Lets return to the example of the pastry versus three dollars. Most of us like the taste of pastries, yet we also recognise they're unhealthy. The benefit of eating a pastry is its reward value: We want it, we like it. This is a benefit you experience immediately as you bite into the pastry.
The costs of eating a pastry, on the other hand, are all incurred by your future self. For most of us, eating that pastry takes us one small step closer to obesity and ill health in the future. Also, what could you have done with those same three dollars next week? Would spending them take you slightly closer to defaulting on your rent or mortgage?
This is an example of how your nonconscious, intuitive brain competes with your conscious, rational brain. Your intuitive brain has no concept of the future and no understanding of abstractions like health and finances. It wants to eat things that taste good, right now. Your rational brain on the other hand, understands the value of the future, and other abstract notions like obesity and money. It wants to protect you from the excesses of the intuitive brain; it wants your future self to be lean, healthy and rich"

The Hungry Brain P.1083

Law abiding
Self control
Sense of purpose
Achievement and satisfaction
— The Chimp Paradox, P.36.

What Guyenet is describing in the passage above is the playoff between your chimp brain (nonconscious, intuitive) and your human brain (conscious, rational).


Professor Steve Peters describes how the chimp brain is up to 5 times more powerful than the human brain. Does this mean that we have no control over the irrational, impulsive hungry chimp at all? Not necessarily, the winner between the chimp and the human when faced with a pastry to a great extent comes down to a psychological trait known as 'delay discounting'. This principle is demonstrated in the landmark 1970 Stanford Marshmallow experiment some might describe as bordering on child abuse4,5.

Children were offered a choice between getting one marshmallow now, or two marshmallows in 15 minutes. During this time the child was left alone with the single marshmallow, the temptation was intense but what researchers really wanted to see was whether they could resist an immediate reward for a delayed, greater reward. 

Whilst child abuse might be a bit extreme (it had ethical approval!) the experiment can be seen in the video below which whilst being very funny, and to some extent cruel, yielded impressive results.

Jumps to opinions
Thinks in black & white
Emotive judgement
— The Chimp Paradox, P.16

As demonstrated, some children covered their eyes, talked to themselves, nibbled tentatively, most popped it straight in their mouth as soon as they were alone and some resisted. 

People who value their future selves highly will value long term goals like leanness and health
— The Hungry Brain, P.109

Those children who were better at delaying their gratification ended up slimmer 30 years later6. In fact, for each minute they were able to delay the marshmallow as a child, they were slimmer by 0.2 BMI points as an adult (a 10 minute delay is worth approx. 15 pounds in adult weight). This makes sense; people who value their future selves highly will value long term goals like leanness and health. That holiday next year is worth more than the pastry now. On the contrary, those who do not value their future selves will value the pastry much more now than a beach body next year3 and are much more likely to have obesity7.

Evidence based
In context & perspective
Shades of grey
balanced judgement
— The Chimp Paradox, P.20

So, we each have a chimp and a human brain, and those who are best at managing their chimp seem to care more about their future health and leanness. The common advice to eat in moderation doesn't seem to align with our genes as discussed in part I.

Explore part III to find out why a varied diet might also be at the root of weight gain.

Luke R. Davies :)


  1. Moseley, L. and Butler, D. (2017). Explain Pain: Supercharged, Noigroup Publications, Adelaide, Australia.
  2. Peters, S. (2012). The Chimp Paradox; the Mind Management Programme for Confidence, Success and Happiness, Vermilion, Ebury Publishing, Croydon, UK.

  3. Guyenet, S. J. (2017). The Hungry Brain: Outsmarting the Instincts that Make us Overeat, Vermilion, Ebury Publishing, London, UK. 
  4. Mischel, W. and Ebbesen, E. B. (1970). Attention in Delay of Gratification, Journal of Personality and Social Psychology, 16(2), P.329-37. (cited in REF. 3, P.108)
  5. Mischel, W. and Ebbesen, E. B. (1972). Cognitive and Attentional Mechanisms in Delay Gratification, Journal of Personality and Social Psychology, 162(1), P.204-18. (cited in REF. 3, P.108)
  6. Schlam, T. R., Wilson, N. L., Shoda, Y., Mischel, W. and Ayduk, O. (2013). Preschoolers Delay Gratification Predicts Their Body Mass 30 Years Later, Journal of Pediatrics, 162(1), P90-93. (cited in REF. 3, P.109)
  7. Jarmolowicz, D. P., Cherry, J. B. C., Reed, D. D., Bruce, J. M., Crespi, J. M., Lusk, J. L. and Bruce, A. S. (2014). Robust Relation Between Temporal Discounting Rates and Body Mass, Appetite, 78, P1394-99. (cited in REF. 3, P.109)