Have you ever heard of the terminology ‘brainless thinking’? We all know what it refers to…But how about taking it really seriously? There are certain animals which do not need a brain for learning and thinking properly! This is the surprising discovery that Prof. Simon Sprecher of the University of Fribourg has laid out in a recently published study. With his team, the biologist was able to teach sea anemones to adapt their behaviour based on past experiences.
We always associate the faculties of learning and memorization with the existence of a brain. Indeed, science already knows quite a lot about the various functions located in different areas of the brain. However, not all animals possess a brain. Cnidarians like anemones, jellyfish and corals have a rudimentary nervous system. “We often suppose then, a bit naively, that these creatures can only behave at the level of reflex,” Prof. Simon Sprecher of the Department of Biology at the University of Fribourg explained. In a recently published study in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS), Dr. Sprecher and his team made clear that the supposition is simply not true. They successfully proved that the starlet sea anemone is endowed with a kind of simple memory and that it is able to learn through association.
Associative learning
The research group carried out tests on animals, subjecting individuals to light and electric stimuli simultaneously (light flashed and electric “shock” administered together) to create an interval between the two so that no link would be perceptible. This constituted training which the anemones did indeed react to. Over time, those that had received the two stimuli simultaneously retracted their bodies as soon as the light pulse was emitted. They had learned that a flash of light was accompanied by an electric shock, classic Pavlovian conditioning. The cnidarians were therefore able to register in some kind of memory a link between two elements and adapt their behaviour accordingly. “This is exactly what is called associative learning, proof that even animals without brains are able to display complex behaviour thanks to their nervous system,” Dr. Sprecher said.
“So we have the necessary framework,“ he added, “to push our research further.” Now that we know creatures without brains are capable of learning, a question arises. How do they do it? There is a hypothesis that certain synapses are reinforced in them as well.” Does there exist a kind of nervous centre? Are there zones that are mainly devoted to organizing the process of learning? Or is the entire process spread uniformly throughout the whole body? Unfortunately, the answers to such questions( crucial for clarifying the mystery) haven’t been found yet.
Learning to learn
Learning is a change in behaviour as a result of experience, and it can come in many forms. At one end of the spectrum sits non-associative learning. Familiar to anyone who has “tuned out” the background noise of traffic or television, it involves turning up (sensitizing) or dialling down (habituating) one’s response with repeated exposure.
Then there is associative learning(explained earlier), in which a cue is tied to a behaviour. Just as the sound of a chip packet brings a dog running or just like the smell of nectar invites pollinators to forage for a sweet reward.
We can add conceptual, linguistic and musical learning, which demand complex coordination and the ability to reflect on one’s own thinking. They also require specialized areas within the brain, and a large number of connections between them. So, to our knowledge, these types of learning are limited to organisms with sufficient “computing power” – with sufficiently complex brains.
The presumed relationship between brain complexity and cognitive ability, however, is anything but straightforward when viewed across the tree of life.This is especially true of the fundamental forms of learning, with recent examples reshaping our understanding of what was thought possible.
No neurons, yet no problems
Stretching our instincts further, evidence now abounds for learning in organisms that lack even the neuronal building blocks of a brain.
Slime moulds are single-celled organisms that belong to the protist group. Recently (and inaccurately) popularised on TV as zombie-making parasites, they also offer a striking case study in what the brainless can achieve.
Experiments have documented a suite of cognitive tricks, from remembering routes to food, to using past experience to inform future foraging, and even learning to ignore bitter caffeine in search of nutritious rewards.
Plants too can be counted among the brainless thinkers. Venus fly-traps use clever sensors to remember and tally up the touches of living prey. This allows them to close their traps and begin digestion only when they’re sure of a nutritious meal.
Learning, then, is not the sole province of those with a brain, or even the rudiments of one. As evidence of cognitive prowess in the brainless continues to accumulate, it challenges deep intuitions about the biology of sensation, thought, and behaviour more generally.
The implications also reach beyond science into ethics, as with recent advances in our understanding of nociception, or pain perception. Do fish, for example, feel pain, despite not having the requisite brain structures like those of primates? Yes. What about insects, with an even simpler arrangement of an order-of-magnitude fewer neurons? Probably.
And if such organisms can learn and feel, even if it is in ways unfamiliar to us, what does it say about how we treat them in our recreational, research and culinary pursuits?
Another mystery arises…
These observations raise another question. When and how did the ability to learn to emerge in evolution? “The first ancestors of all the animals that possess a brain lived around 560 million years ago. Those endowed with a nervous system appeared 100 to 150 million years before that,” Dr. Sprecher pointed out. Have animals that are capable of learning existed for even longer than we have thought until now? “That is a very interesting question that certainly deserves study.”
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