Intelligence: thinking with different brains

Image credit: Pixabay

Intelligence seems to be a concept we are smart enough to conceive, yet struggle to comprehend. In daily life, we understand that intelligence comes into play in the way we plan our day, solve problems, or navigate a new city. To an extent, we are also able to recognise intelligent behaviour, for example, in a toddler learning how to speak.

Little, however, is known about how our brains give rise to these cognitive powers – how its cells, their connections and physiology, enable us to think in the way we do.

Across the animal kingdom, many instances of intelligent behaviour can be found. Looking at these different brains has helped scientists in figuring out our own.

Birds, especially some parrots and those from the crow family, display many forms of intelligent behaviour, such as tool-use and possibly even recognising themselves in a mirror, as reported in 2008 by Prior and colleagues. The small size of their brains, however, leads us to question the basis for their intelligence. A study led by Olkowicz has shown that the brains of some birds have an extremely high number of neurons, a large proportion of which are located in the forebrain, where most cognitive processing takes place. In fact, these birds have a higher density of neurons than mammals and in some cases more neurons in the forebrain than primates. The scientists suggest that the different layout of the avian brain, with its neurons packed together more tightly than ours, may contribute to faster processing speeds and increased mental capacity.    

Octopuses are a surprising addition to the list of intelligent creatures, considering how different its brain and body are from ours. In the laboratory and in the wild, octopuses exhibit a wide range of intelligent behaviours. An intriguing example is its carrying of coconut shell halves for future use as shelter, reported by Finn and colleagues in 2009. More recently, a sequencing study of the octopus genome led by Albertin revealed that octopuses have much higher gene numbers in 2 gene families compared to its close relatives. One gene family, the protocadherins, is important for neuron development and function. The other family regulates gene expression. These and other molecular peculiarities provide some clues as to why octopuses are so smart.

From another perspective, we can also look at what makes animals not as smart as we are. The elephant has a massive brain compared to ours, but its level of intelligence does not match up. A study led by Herculano-Houzel offers an explanation – the researchers have found that a large proportion of elephant neurons are found in the cerebellum, a structure important in the coordination of movement. However, in the cerebral cortex, where thinking takes place, elephants have much fewer neurons than humans. This suggests that the distribution of neurons is an important factor contributing to intelligence.

Artificial neural networks give us a whole new look at intelligence. The idea for these networks came from our own brains, and they are now teaching us more about ourselves. Recently, a study by Aram and colleagues has used chaotic artificial neural networks to propose a model of how memory works. Neural nets are sophisticated computational tools that can be used as a model for how the human brain works at the level of networks of neurons.  

The challenge with all these data is to string them into a coherent story. Brains can be studied on different scales – from molecules and cells to local networks and entire brain regions, or even on a computer. Scientists may specialise in one aspect of study; for example, a biochemist will look at individual proteins. However, to link atomic changes to intelligent behaviour will require cross-disciplinary cooperation, as will integrating computational models into a biological context.  

Despite the difficulties involved, the potential for a deeper insight into our own minds continues to drive research forward. The study of a wide range of brains can give us an appreciation of the myriad different ways of thinking that have developed, and in so doing, expand our notion of intelligence itself.  

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