Does the Behavior of Certain Plants and Fungi Show That They Value Certain Things?

Original text Luciano Carlos Cunha · Volume VI, p. 51 of the PDF edition · English translation

Certain nonsentient living beings exhibit certain behaviors. For example, plants absorb nutrients from the soil, carry out photosynthesis, some close and open in response to touch or light, and so on. There are also studies suggesting that plant growth is affected by sound stimuli, such as speech and music⁶². There is a common belief that these behaviors show that such organisms are sentient, or else that they have intentionality and a will to remain in this or that state, even if they are not sentient. What follows is an explanation of why this common belief is mistaken.

The presence of behavior does not necessarily imply that there is sentience or valuing. For example, a thermostat reacts to changes in temperature, but this does not imply that the thermostat values being at this or that temperature, or that it has a will to remain in this or that state. It implies only that there is this reaction to a certain stimulus. In fact, there are robots that exhibit behaviors very similar to those of humans. But that by itself does not show that they are beings who value certain states or have a will. The same holds for certain plants that close when touched or grow in response to certain sounds: this does not necessarily imply that the plant likes or wants to be in this or that state. It does not imply that there is necessarily someone there. These behaviors can be explained as the result of physicochemical reactions.

Sometimes the terms used in certain studies of plants or fungi can be ambiguous and mistakenly suggest that plants or fungi are sentient, when that is not in fact what the study shows. For example, certain species of fungi emit electrical signals. In one study, the sequences of these signals were decoded and called a “language”⁶³. When we hear the word language, we normally already assume that there is an individual, a conscious being, who understands the symbols, assigns meaning to them, and uses them to communicate what is going on in their mind. The same study states that “electrical activity is used by fungi to communicate.” This may suggest that the signals are used intentionally by the fungi, that fungi are someone, that they have

consciousness, etc. However, the term “language,” as used in the study, has the same sense as in artificial intelligence: it refers only to something that, although quite complex, may very well occur without being accompanied by any consciousness at all. In this sense, the electrical signals are “used by fungi” in the same sense in which a computer program “uses” input data to perform certain activities. This does not necessarily imply consciousness⁶⁴.

It could be objected that, just as it is possible to explain such behaviors as the result of physicochemical reactions, it is also possible to explain them on the assumption that there is a will or consciousness in these beings. However, the fact that an explanation is possible does not show that it is necessarily correct. The point here is that such behaviors can be explained without having to assume that these organisms are sentient. This is different from what happens, for example, in the case of invertebrate animals⁶⁵ such as insects, crustaceans, and arachnids. In their case, it is very difficult to explain their behavior without having to assume that they are sentient. Moreover, these animals, unlike plants or fungi, have a physical structure (a centralized nervous system) that performs the function of processing the information reaching the organism and creating the conditions for consciousness to arise⁶⁶. In the case of beings that have no nervous system (nor anything performing an analogous function), on the other hand, there are reasons to suppose that their behavior is the result of reflexes. This will be explained in more detail below.

Because they experience certain states as positive and others as negative, sentient beings behave in certain ways (they avoid what would cause them negative experiences and seek what would cause them positive experiences). However, the fact that there is a certain behavior is not sufficient to conclude that an organism is valuing something. Even in the case of sentient beings, it is possible for their sentience to be absent at a given moment (for example, under general anesthesia) while the body still continues to exhibit certain behaviors due to reflexes.

This works this way because of what are known as reflex arcs⁶⁷. Consider, for example, the tap on the knee with a reflex hammer given during a medical checkup for a driver's license. When the information about the tap reaches the nervous system, it travels along two paths. One, shorter and more direct, goes from the spinal cord to the muscles. The other, longer and more indirect, goes from the spinal cord to the brain, where the information is processed and the conditions for the experience to arise are created. This is why the knee reflex is instantaneous, while the sensation arrives a little later.

There are certain nervous systems that operate in a way similar to reflex arcs, but without the sensation part. For example, there are certain animals, such as jellyfish and sea cucumbers, that have nervous systems but have no brain or any other organ that performs its function⁶⁸. These animals exhibit reflexes (and sometimes relatively complex behaviors), but this is not an indicator that they have experiences. A similar mechanism appears in certain organisms that have no nervous system, such as carnivorous plants and sensitive plants (mimosa), for example.

Thus, the lack in these organisms of a physical structure that performs the function of creating the conditions for experiences to arise, together with the presence of reflexes, is a strong reason to conclude that the existence of behavior, by itself, is insufficient to conclude that the organism in question is sentient, that it is valuing certain states, or that it is expressing a will.