If A Plant Is Smarter Than AI? Deciphering All The Intelligence Of Our Planet

MADRID — Chimpanzees in the Congo region have developed a precise technique for hunting termites. First, they use a sturdy stick to dig a deep tunnel in the hard soil and reach the insect colony. Then, they take the stem of a specific plant and break it down with their teeth to form a kind of brush they will use, like a fishing rod, to catch the termites in the hole they just dug. 

But their intelligence goes a little further: This know-how does not arise spontaneously in all chimpanzee populations but has spread over time with exchanges among groups. According to a study by the University of Zurich published late last year, these apes transmit their culture and advances among each other in a way that is not dissimilar to how we humans do it. 

It is difficult to doubt the intelligence of chimpanzees. It’s also hard to doubt that of orangutans — with their medical knowledge — and of dolphins, with their ability to solve complex problems. Anyone who has spent a good deal of time with a dog likewise has few doubts about canine intellectual capabilities. But is an octopus intelligent? What about a bumblebee, or even a plant? 

Defining intelligence

“When we look for intelligence in other living beings, we usually study those that are most similar to us, Homo sapiens,” says Paco Calvo, head of the University of Murcia’s Minimal Intelligence Laboratory — MintLab. “We observe apes and other mammals. But our strategy — here — is the opposite: We study those least similar to us,” he says, adding, “because when we find someone who, without resembling us at all, is capable of solving problems, we may then find a master key that will help us understand intelligence in any branch of the tree of life.” 

Calvo’s laboratory is a unique institution, part scientific and part philosophical in its vocation, which seeks to determine what exactly we mean by intelligence and to define which living beings can show signs of it. The title of Calvo’s 2023 book Planta sapiens, already tells us where this is going.

Is a climbing plant intelligent? The first answer that comes to mind is: no, obviously. But perhaps we are not intelligent enough to understand the other forms of intelligence with which we share the planet.

It’s much easier for us to think of ChatGPT as intelligent than a plant.

The main problem for scientists studying intelligence is to manage to free themselves from their own human vision — or stop using themselves as yardsticks. If a living being communicates like us, solves problems like us or is even capable of imitating our behavior, it is intelligent. But that doesn’t have to be the only valid way of being intelligent. 

“It’s much easier for us to think of ChatGPT as intelligent than a plant, simply because we can hold a conversation with it,” Calvo says. “But that is not what being intelligent means, nor is it about having neurons or even being able to move. That’s why we try to find that common denominator, those signs that there is sentience and intelligence, regardless of the evolutionary strategies that have led that living being to become what it is,” he says.

For Calvo, a cognitive biologist, there are three minimum signals or three behaviors that indicate we are dealing with an intelligent being: the ability to integrate all the stimuli received at a given moment and generate a response; the ability to anticipate a situation; and the ability to pursue a goal.

“We don’t see intelligence directly, not even our own, but rather we see behavior and infer whether or not it’s intelligent. If you see me knock myself into a wall 23 times, you’ll think: ‘Paco seems a bit stupid.’ But if I change strategy to avoid the obstacle, you’ll think I’m intelligent,” explains Calvo. “The same applies with plants.” 

Integration and anticipation

The first sign of intelligence is sensory integration, that is, the ability to respond based on a multitude of stimuli that are integrated. If a plant receives light and always generates the same response, we could be dealing with an automatic reaction. But if the response is different in each situation, adapting to the context based on light, temperature, chemicals in the air and soil, the force of gravity or threats, all processed simultaneously, we can understand we are not dealing with something automated.

“That doesn’t mean there’s someone at the helm of the plant ship, which is how we usually think of intelligence. There’s no one running our brains either,” Calvo adds. “What this means is that a plant is capable of integrating information and providing flexible responses that adapt to the situation. Just as mammals do, but also birds, reptiles, bacteria and fungi. And that’s a way of displaying intelligence,” he says.

Another sign is the ability to respond in anticipation, meaning that responses are not just reactions to something happening but also to something that will happen in the future. Just as we are able to understand the trajectory a ball will follow and prepare to receive it, other intelligent beings can also, somehow, anticipate the future.

“This ability is essential for a plant, which cannot react quickly or move. It has to understand which direction it should grow on the basis of future developments and how its objective will change,” he explains.

Pursuing goals

And this is where the third key comes into play: goal-directed behavior. In other words, intelligent behavior cannot fumble along blindly until its objective is reached; rather, it must be clearly directed toward that goal. At the MintLab, they analyze the movements of climbing plants using time-lapse techniques, taking regular and continuous photos, and then using time-lapse to study their movements on a humanly comprehensible scale. That is where intelligence reveals itself.

“There we see how the plant controls its growth pattern, moving in one direction until it approaches the support and when it gets close, it slows down slightly to reach it in a controlled manner. If we move the support at that moment, the plant modifies its growth pattern. All of this requires internal control and anticipatory and flexible behavior,” Calvo explains. “The plant must be alert, like an animal and just as we are. Be careful, things happen and situations change.”

In addition to photography, another way to study plants at the MintLab is to analyze the electrical signals running through their interior. While plants have neither neurons nor synaptic connections, this does not mean there is no internal communication.

“We can study these electrical impulses and understand what responses they generate. The time scale changes, the ions change and the tissues change, but there’s a communication system in which we even find many of our own neurotransmitters,” the researcher adds.

Rethinking human intelligence

Plant communication not only works internally, but is also directed at other living beings. Plants for example can emit warning signals in the presence of a predator, so other plants can prepare. Some even generate chemical signals that attract other predators capable of eliminating the threat. Furthermore, the response of plants depends on each individual; in other words, they have something we could call personality.

“A plant is not a pre-programmed robot that will always respond the same way. Two plants that have different learning histories or are in different contexts respond differently. They are not personalities like humans, but they are personalities,” Calvo explains.

“Furthermore in the case of plants, it is difficult to know where the individual begins and ends because their intelligence is very decentralized. They cannot run away to preserve their organs, like we do, so their strategy is not to have anything essential located in a specific place. Therefore, we can understand each plant in communal terms,” he says.

It’s not enough to say that we’re clear about who we are and that plants are different.

And this collectivity extends beyond the plant, as plant communities also exhibit collective behaviors. For the researcher, all of this is grounds for rethinking our own intelligence. “A flock of starlings or a school of fish display complex collective behavior, but there’s no one in charge. They display emergent properties, where the whole is greater than the sum of its parts. Everything interacts with everything else, and a pattern emerges from that, without a conductor,” he adds.

“This helps us rethink ourselves. It’s not enough to say that we’re clear about who we are and that plants are different. We have to rethink what human intelligence consists of,” the researcher concludes.

Human beings, he says, “are more decentralized than we think. Consider, for example, the connection between the gut microbiota and the brain. We used to believe our decisions came only from the brain, but in fact there’s an information superhighway that connects us with the gut and with a multitude of microorganisms that aren’t human but are equally at the helm of the ship. Our behavior is also, in some way, the result of a multitude of interactions.”