The similarities between the brains of humans and other species

by Marc Wilson / 10 November, 2018
Illustration/Getty Images

Illustration/Getty Images

RelatedArticlesModule - Human brains species

Humans are different from other species, but not as much as we’ve assumed.

“It makes you think” used to be a sales pitch for the University of Wellington. I assume that is because going to university makes you think. I loved it, because it lent itself to so many variations relevant to the marketing of psychology. I still have my “Your brain – it makes you think” t-shirt. It’s a collector’s item.

Brains are rubbery things, and, probably to gasps of my colleagues who work more closely with them, I think it’s safe to say we’ve not got a complete handle on how they work.

Which isn’t to say we don’t know quite a lot. We know that different bits are associated with different faculties. For example, the amygdala, buried deep and just behind the eyes, is associated with processing emotions. The prefrontal cortex (PFC) is the bit up front and that’s important for complex behaviours like decision-making.

We share a lot, but not all, of this gear with other species. Monkeys also have amygdalas. Since at least the 1930s, we’ve known that monkeys without amygdalas behave quite differently from their intact peers. For instance, they don’t shy away from snakes and other dangerous animals. Instead, they play with them. Animals without amygdalas lose their sensible sense of fear.

The same thing applies to us. One particularly relevant case is that of “SM” (brain folk give their cases initials like this). SM has an unusual condition that means she has no amygdala. If the amygdala is useful for generating fear, and fear is a sign that there is danger, it’s no surprise that SM finds herself in trouble without realising it. In one account, she would walk through the same park where she was mugged only the day before.

For a long time, it’s been thought that not all animals have as extensive frontal lobes as us. Ours are generally large relative to our total brain volume, but not our body size. Some lap dogs and fish do better on the latter measure than we do. Although it’s still generally the case, there’s less reason for us to feel superior to other species on the basis of large frontal lobes alone – our PFCs are about as proportional to the size of other brain structures as they are in other primates.

For a long time, in our hubris, we also thought that we were the only species to exhibit cerebral asymmetry – two hemispheres of the brain that do different things. The classic example is language, the heavy lifting for which is done by one hemisphere or the other. For the majority of people, it is done by the left side of the ol’ burger.

Even split: A Caledonian crow. Photo/Getty Images

Even split: A Caledonian crow. Photo/Getty Images

Another example is handedness. The muscles on each side of our body are controlled by the opposite hemisphere, so a right-handed person is typically left-hemisphere dominant. There is now abundant evidence of lateralisation across a good number of other animal species.

This brings me to bird brains. Many people would say that we should share more in common with primates than, say, the crow that harasses my dog from the garage roof. But there’s some fascinating research that shows that crows are also lateralised.

Caledonian crows dominate these discussions because they make and use tools to pry bugs out of crevices and they show a preference for which side they hold and use their tools.

However, crows and other species that show lateralisation are typically about 50:50 left or right dominant. So, rather than focusing on how we’re specially different from other species, questions tend to centre on why we have a hemispheric dominance that results in most of the population being right-handed.

This article was first published in the October 27, 2018 issue of the New Zealand Listener.


Win the 100 Best Books of 2018
99119 2018-11-16 00:00:00Z Win

Win the 100 Best Books of 2018

by The Listener

Each year, the Listener offers one lucky subscriber the chance to win all 100 of our Best Books.

Read more
Full of light and art, Forestry Cafe is south-east Auckland's newest coffee spot
99142 2018-11-15 16:49:34Z Auckland Eats

Full of light and art, Forestry Cafe is south-east…

by Alex Blackwood

New opening Forestry Cafe brings a city vibe to Flat Bush.

Read more
Turning a corner: Why this wayward Auckland teen stayed in school
99114 2018-11-15 10:34:07Z Social issues

Turning a corner: Why this wayward Auckland teen s…

by Vomle Springford

When Acer Ah Chee-Wilson was 14, he wanted to be in a gang.

Read more
What Kate Sheppard said that changed the course of New Zealand politics forever
99084 2018-11-15 00:00:00Z Politics

What Kate Sheppard said that changed the course of…

by Noted

Helen Clark and even Meghan Markle have quoted Kate Sheppard – what did she say that was so powerful?

Read more
Why Bret McKenzie is going straight with a new band
99026 2018-11-15 00:00:00Z Profiles

Why Bret McKenzie is going straight with a new ban…

by Russell Baillie

After a year of stadium comedy and Muppet shows, Bret McKenzie talks about returning to his music roots in a band whose songs are no laughing matter.

Read more
The weight-loss industry is trying to rebrand itself as the 'wellness' industry
98751 2018-11-15 00:00:00Z Nutrition

The weight-loss industry is trying to rebrand itse…

by Jennifer Bowden

As dieting is exposed as the lie that it is, the weight-loss industry is unravelling.

Read more
Best of Wellington: What to do in the capital
98651 2018-11-15 00:00:00Z Travel

Best of Wellington: What to do in the capital

by Metro

A round-up of great things to do in Wellington, plus where to experience the best of capital culture and tips on where to stay.

Read more
Douglas Wright: 1956-2018
58688 2018-11-15 00:00:00Z Listener NZ 2004

Douglas Wright: 1956-2018

by David Eggleton

The celebrated NZ choreographer has died after a long illness. David Eggleton describes the path of Wright’s creative life from Tuakau to New York.

Read more