In reporting on a recent bushwalk she and her husband had done, my daughter Wendy mentioned with some excitement that they had seen a Lyrebird. She added, almost as an aside, “and a snake”. (Experiences with snakes in Nepal as well as Australia have helped her to be reasonably matter-of-fact about the creatures)
Australia is home to almost all of the 10 most venomous species of snakes in the world. But Australian snakes do not pose a serious threat as they are shy creatures that avoid contact. Nevertheless, we are alert for snakes, especially during the warmer months, like now. Unfortunately a fear of snakes discourages some Australians, especially newcomers, from venturing into our beautiful bushland.
I talk about the fear of snakes later in this post but first I provide a context, which inappropriate as it may first appear, has to do with our love of living things.
I was greatly entertained this week by a video of Wendy’s granddaughter, Zoe, having “quality time” with her new pet rabbit, Peter. She squatted beside Peter (much as she is doing in the photo), gently patted him and then attempted a “cuddle” and a kiss.
Zoe has grown up with dogs in her life and loves animals.
This is not at all surprising or unusual because, like all of us, she was born with a brain that has a positive bias towards living things.
From as early as four months of age, infants pay more attention to animals than to toys including furry toy animals. And they are equally attentive to snakes – with no sign of fear.
Why then do human (and other primate) adults usually have a fear of snakes that is stronger than the fear of almost anything else? It may appear to be a rational or intellect-driven fear because snakes are known to be capable of harming or killing humans. But so too are guns and knives. What’s more, the fear of snakes resides in many people who have little or no contact with them. So what’s going on?
An answer that is gaining increasing scientific support is contained in the “snake detection theory” which is based on the idea that evolution has given us brains that are “prepared” to learn very quickly to fear snakes.
Researchers at the University of Virginia, Vanessa LoBue and Judy DeLoache, have pioneered the study of the origins of the fear of snakes in children. They report that children are very good “snake detectors”. Shown a set of eight photos – seven depicting caterpillars and one showing a snake – three-year-olds were quick to find the snake photo. By contrast, they took longer to find the caterpillar in a group of snake photos. The same thing happens when the children were asked to distinguish snakes and frogs. Picking out snakes seems to be easier, especially so, according to another of LoBue and DeLoache’s studies, if the snake is moving in its characteristic writhing motion.
The posture of the snake may also affect the speed of detection. Using a task that required people to pick out a snake image from an array of flower images, Nobuo Masataka and his colleagues found that both children (aged 3-4 years) and adults were faster identifying snakes if the snakes were shown in an attack position. According to their parents, the young children in this study had never been exposed to snakes before. Not only had they never seen a real snake, they’d never seen any images of snakes, or toy snakes.
These findings point to the likelihood that humans are hard-wired to be quick at detecting snakes and possibly other potential predators such as crocodiles. Snake detection theory goes a step further, however. It proposes that snakes have played a major role in the evolution of our brains, specifically our incredibly complex and accurate visual systems. Both snakes and primates, including our species, evolved in tropical regions and had plenty of opportunities to interact. Snakes are hard to spot, so if their threat was strong enough, natural selection might have favoured primates with keen eyesight and quick reaction times.
The neurological evidence supporting this theory is starting to be uncovered. At the base of the brain, there is a very busy visual relay centre called the pulvinar region. Compared to that in other mammals, this region is disproportionately large in humans and primates. It is thought that the pulvinar is particularly important in picking out important visual information in cluttered environments.
To test this idea, researchers inserted probes into the brains of captive-bred Japanese macaques who had never encountered snakes. Activity in the pulvinar region was monitored as the macaques were shown various images – monkeys’ faces, monkeys’ hands, simple geometric shapes, and snakes – under carefully controlled conditions. The pulvinar region was found to be especially attentive to images of snakes. It didn’t matter whether the snakes were coiled up or stretched out; the macaques’ neurons responded similarly to snakes in each position. Since these monkeys had never seen a snake before, the neural responses appear to be hard-wired rather than a result of experience.
Another response that appears to be hard-wired into the human brain completes the biological foundation of our fear of snakes. LoBue and DeLoache demonstrated the link in infants in the first year of life. In a landmark study, they presented infants with videos of moving snakes paired with videos of other animals – giraffe, rhinoceros, polar bear, hippopotamus, elephant, and large bird – moving at the same speed. The videos were played under two different conditions – accompanied by either an audio track of an adult sounding fearful or one in which the adult sounded happy.
When the happy voice was playing, the infants paid no more attention to the snake than to the other animals, but with the fearful voice, their attention was directed much more on the snake.
What LoBue and DeLoache appear to have shown us is that the human brain has evolved to learn more quickly about certain kinds of animals – those that have posed the greatest threats to our ancestors. Maybe it takes very little to trigger fear (and other negative feelings) where snakes (and possibly other threatening creatures) are concerned. We see friends or family acting fearfully and we are persuaded very quickly to adopt the same behaviour. As Martin Seligman proposed over 40 years ago, animals, including us, are “prepared” to learn some lessons very fast.
Our fear of snakes is just one small aspect of the amazingly complex way in which our thoughts, feelings and behaviour are influenced by nature. Reflecting on this, the architect of the biophilia concept, E.O. Wilson says,
We’re coming to realize that there’s something a lot more complicated and deep and wondrous in the development of the human mind, than what we had imagined.
Ours are minds, Wilson adds, that have “a strong residue of the environments in which we evolved”. And those are natural environments.
Somewhat like the tracks on a CD that are moulded by an environment of sound, our brains have been richly and subtly attuned to natural environments. And just as a CD requires the right kind of player to perform, the human brain responds optimally to the stimulation of nature.
That is why our brains have the strong positive bias towards nature we see in infants like Zoe. The image of Zoe reaching towards Peter captures something of that bias and is a symbol of what our brains would have all of us do – embrace nature and be showered with benefits for doing so.