A study challenges the conscience of the plant on a test bench

The cry of the carrot is back on the front of the stage.

You’ve probably heard this argument go in the middle of a passionate debate between a vegan and a meat eater : “But what is it that tells me that the plants do not suffer when we eat them ?”


A reflection sometimes formalised under the name “cry of the carrots”, in reference to the alleged ability of plants to feel pain. This is an argument debatable, often presented in a rude way to ridicule the movement vegan. But to believe in the paper opinion produced by a team of researchers led by Lincoln Taiz, university of California, this concept would simply not have scientific basis. A good opportunity to dissect their publication to get an idea of the scientific bases that underpin this problem of controversy.


Nevermind the squabbles between friends for stories of conviction and diet. In science, the problem of the “cry of the carrots” does not date from yesterday : in the 18th century, we begin to see the emergence of a current of thought named “the Biology of romance”. This movement has been codified by the German philosopher, Schelling, in a book called “Naturphilosophie”. Their ultimate goal : to prove that the nature and spirit are one.



The impossible consensus around the “neurobiology of plants”


Today, the different schools working on the subject have a major problem : they are unable to agree on the terminology. There are sticking points on many of the lexical elements, that make it very difficult to find a consensus.


The first is already in the name of the discipline that studies these phenomena. A first group talks about the “neurobiology of plants”, and does not hesitate to draw in the lexicon of neurobiology animal to support his arguments. In contrast, a second group ( including the authors of this study) considers that this terminology is incorrect : according to them, the absence of a nervous system in itself is sufficient to render the name obsolete. We distinguish here the two camps are clearly defined.


The second point of debate is the use of the term “intelligence” when talking about plants. Historically, the scientific community was initially very fiercely opposed to this term because it was considered the intelligence as a term reserved for the faculties allegedly superior to the human. Today, the problem is still very complex : a study speaks even of more than 70 forms of intelligence. The definition of the more generic possible, so that it encompasses all of these concepts, is the ability to “receive and interpret information from its environment”. Problem : according to this definition, single cells would be so smart. And beyond : some organelles (comparable to the “organs” of plants as chloroplasts are also responding to this definition !


As long as the different schools of thought will not be able to agree on a terminology that is clear, it will in any case be difficult to arrive at a consensus. Then, true similarities or bias of reasoning ?


However, some plants show well and the abilities that one would be tempted to interpret as a form of intelligence or sensitivity. We know for example very well that plants communicate through different signals chemical, as in a same organisation as between them. There are even examples even more impressive : the trees “social” capabilities of calculation, the examples of such behavior abound. But is it really a “behavior”, which includes the concept ofintentionality, rather than physicochemical reactions ? Nothing allows us to affirm at the present time.


Then when one notes the number of studies that speak of systems, “articial nervous” without a true nervous structure itself has been identified, a question arises : should we not too much inclined to want to see in plants mechanisms that strongly resemble those that we know in humans ?


This way of reasoning is, however, well known, and bears the name ofanthropocentrism. It means “the fact of putting the human at the centre”, and by extension, tounderstand reality through human perspective. To avoid this danger, the ecologist Monica Gagliano has conducted a series of experiments intended to demonstrate that it was possible to conduct experiments of habituation and pavlovian conditioning on the plants. In these experiments, plants have “learned” to extend their leaves to anticipate the arrival of a light source. The results are quite controversial , which have, however, been sufficient to assert that it was’a form of intelligence and conscience : for it, the signaling électrioque and chemical that are found in plants, fulfills this same function.



No reason to develop a conscience !


A premise rejected by the team of Taiz, which reminds us that the concept of consciousness is intimately linked with the development of a central nervous system, with a high level of specialization. This comparison would be an approximation not really relevant, extrapolation produces a form of anthropocentrism.


But the team of Taiz does not just attack the arguments of many studies of Gagliano, and other researchers more inclined to speak of the “nervous system” and “consciousness” in plants. It advance, especially a very strong argument : they would have had no reason to develop one !



The plants […] are adapted to be examples to follow in terms of energy efficiency, based on the absorption of water […] rather than on the synthesis of proteins which are very costly in energy. They have not evolved to hunt prey or escape their predators. […] There is no evidence that the plants are in need of mental abilities that cost energy as consciousness, feelings and intentionality to replicate and survive.



It is indeed one of the creeds of evolution : which consumes more energy than necessary is necessarily less suitable, and therefore less likely to be subject to natural selection. But by intellectual honesty, the team said the same in his study that to exclude rigorously the question of consciousness in plants, it should first have a clear idea of the “level of functional complexity and need for organizational consciousness in animals”.



A case against anthropocentrism


The team of Taiz refuses, therefore, to accept the idea of a real shape of cognition in plants, in the absence of irrefutable evidence. It closes, not, however, the door to the idea. But in addition to the simple theme of the intelligence and cognition of the plants, there is a second reading possible of this fascinating article. You can interpret it as a plea against anthropocentrism, it truly a plague on intellectual, which is able to corrupt a scientific reasoning is in appearance consistent and documented. Monica Gagliano actually costs because it represents an example particularly relevant, but it should not take this study as an expense only directed against this researcher and his work. It is the thread of the construction of a study is very well conducted, combining a discount in historical perspective very fine, the question of the awareness of plants to that of anthropocentrism in general.


They defend a purely analytical and pragmatic, devoid of feeling and human considerations.



we will issue an objection firm about the fact that the consciousness, the intentionality, and cognition are the moral and ethical issues; A scientific understanding of nature is the only thing you need to search for the truth.



The study ends on a conclusion almost philosophical , in the form of an appeal to the patience and intellectual rigour.



Even if the plants don’t have the complexity of nerve required for consciousness in animals, they remain outstanding organizations, worthy of our admiration, respect, education, and conservation efforts. It is already well enough that they are able to convert the light of the day, the carbon dioxide and water into carbon compounds complex, which will bear all the multicellular life on Earth. We should not require of them that they are also aware of the do !



To go further on the themes of the consciousness of the plants and anthropocentrism :



  • Thestudy very thorough team of Taiz, full of historical references and scientific

  • For you to make your own idea, a few studies presenting arguments in favour of cognition in plants : here, here, here, and here

  • A few extreme events in plants that some have interpreted as of intelligence : there, there, there

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