Can We Extend Extended Cognition to Plants?

In my previous post, I discussed the ways apparent cognition can emerge from simple systems acting in parallel, and how the richness of an environment can help generate complex behaviors from seemingly simple organisms. This implies that environments play key roles in cognition and possible behaviors. As we’ll see, a great deal of cognition only occurs through interplay with an environment. What are the implications of this? How far are we willing to take those implications?

A lot of our best thinking happens outside our heads. In The Dawn of Everything, the two Davids, Graeber and Wengrow, point out that “When we are capable of self-awareness, it’s usually for very brief periods of time: the ‘window of consciousness,’ during which we can hold a thought or work out a problem, tends to be open on average for roughly seven seconds. What neuroscientists (and it must be said, most contemporary philosophers) almost never notice, however, is that the great exception to this is when we’re talking to someone else. In conversation, we can hold thoughts and reflect on problems for hours on end. This is of course why so often, even if we’re trying to figure something out for ourselves, we imagine arguing with or explaining it to someone else.”

This point is reminiscent of some of the examples Andy Clark and David Chalmers use in their highly influential 1998 paper “The Extended Mind.” They ask us to “think of a group of people brainstorming around a table,” and to “consider the use of pen and paper to perform long multiplication, the use of physical re-arrangements of letter tiles to prompt word recall in Scrabble, the use of instruments such as the nautical slide rule, and the general paraphernalia of language, books, diagrams, and culture. In all these cases, the individual brain performs some operations, while others are delegated to manipulation of external media.” Rather than lose focus every seven seconds or so, the thought process is mediated through talking to others or manipulating objects. If these people or objects go away, cognitive capabilities decline. Such cognition fully functions only through interaction with an environment. We can thus define “extended cognition” as cognition that declines or disappears if the outside aid is absent. It is cognition dependent on interplay with things beyond our bodies.

If cognition is not bound by the body, but often extends into an environment, to what extent is an environment as a whole capable of cognition? If essential parts of thinking take place “out there,” are there cognitive capabilities “out there,” even without us and our brains? Based on the potential intelligence of simple systems acting in parallel discussed last week, can a collection of simple behaviors from seemingly non-cognitive things generate intelligent systems? Can an ecosystem be intelligent? And if so, as one active part of an intelligent system, are plants capable of extended cognition? A 2019 paper by André Geremia Parise, Monica Gagliano, and Gustavo Maia Souza entitled “Extended cognition in plants: is it possible?” asks just that.

The authors clearly want to say, why yes, yes it is possible. A lot of their examples consist of plants interacting with their environment and altering their behaviors based on those interactions. I find such behaviors endlessly fascinating, but I am not yet convinced we should call them cognition, even when considered as extended cognition (i.e., dependent on interaction with the environment to fully function). They cite a study on root exudates and obstacle avoidance. Some plant roots will release substances into the surrounding soil, and these substances will accumulate in the space between the roots and an obstacle, and the roots will then grow away from the accumulated exudates, thus avoiding the obstacle. The researchers in the cited study removed the exudates, and the plants no longer “knew” where to grow and headed right for the obstacle. Is this really “knowing,” or a simple stimulus and response that falls below the threshold of cognition, even when considered as extended into the environment?

In my previous post, I quoted from an early Rodney Brooks paper, “Intelligence without representation.” Brooks paraphrases Herbert Simon and writes, “The complexity of behavior of a system was not necessarily inherent in the complexity of the creature, but perhaps in the complexity of the environment.” An amalgamation of simple behaviors around and between biotic and abiotic parts of an environment can generate complex systems. As we saw in that previous post about Rodney Brooks, his robots were able to behave creatively and intelligently with just a few simple systems acting in parallel.

Are plants intelligent if they are part of an intelligent system? This is part of the argument from the authors of “Extended plant cognition: is it possible?” Through extension into an environment, where a series of signals and responses from a variety of organisms create a range of clever behaviors, is a plant not behaving intelligently as one part of an intelligent system? If I removed your parietal lobe and put it in a jar, it probably wouldn’t be very smart. But as a part of your body, it really makes you think. Aren’t all the parts of an intelligent system part of its overall intelligence?

We may, however, be making intelligent systems less and less likely to emerge. As we plant endless fields of single crops in lifeless soils, all kept alive by salt-based fertilizers and surrounded by asphalt roads, complex ecosystems capable of collectively intelligent behaviors are less and less likely to appear. By turning complex ecosystems into mono-cropped fields of a single species or tree farms that mainly exist for future lumber for suburban homes that will remain standing maybe the length of the mortgage, we are making the world dumber, just as we are starting to notice how smart it is.