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.


Daffodils is a charming, bittersweet and tuneful piece of Kiwiana
103864 2019-03-22 16:20:19Z Movies

Daffodils is a charming, bittersweet and tuneful p…

by Russell Baillie

Aren’t pop musicals meant to be all sweetness and light? No, not if Daffodils is anything to go by.

Read more
Bill Ralston: The keyword is tolerance – even of those we disagree with
103852 2019-03-22 12:37:05Z Social issues

Bill Ralston: The keyword is tolerance – even of t…

by Bill Ralston

Neither evasive nor hate-filled words are needed in the Christchurch mosque-killings aftermath.

Read more
How young New Zealanders are demonstrating their inclusiveness
103832 2019-03-22 09:47:50Z Social issues

How young New Zealanders are demonstrating their i…

by The Listener

Kiwi students provide an inspirational example of how to embrace diversity in the wake of – and even before – the Christchurch attack.

Read more
I never thought I could be in danger over my beliefs – until Friday 15 March
103824 2019-03-22 00:00:00Z Social issues

I never thought I could be in danger over my belie…

by Fatumata Bah

I heard the stories and anecdotes of racism faced by my fellow sisters in hijab, but it was never at the forefront of my mind every day.

Read more
How to enhance your dining experience – with water
103174 2019-03-22 00:00:00Z Dining

How to enhance your dining experience – with water…

by Metro

A stunning dining experience isn’t just about food and wine. Water plays a big part too.

Read more
Facebook won't give up its insidious practices without a fight
103856 2019-03-22 00:00:00Z Tech

Facebook won't give up its insidious practices wit…

by Peter Griffin

Facebook came under fire for its response to the live-streaming of the Christchurch terror attack, but it's digital nudging that's also concerning.

Read more
In photos: The world unites in solidarity with Christchurch
103800 2019-03-21 15:36:46Z World

In photos: The world unites in solidarity with Chr…

by Lauren Buckeridge

Countries around the world have put on a show of solidarity for the victims of the Christchurch terror attack.

Read more
The tangled path to terrorism
103777 2019-03-21 09:59:55Z Psychology

The tangled path to terrorism

by Marc Wilson

The path that leads people to commit atrocities such as that in Christchurch is twisting and unpredictable, but the journey often begins in childhood.

Read more