The Semantics of Melatonin

Let’s start with a little riddle: What kind of organism has no eyes, no mouth, and no brain, but—arguably—has a mind?

Most of the work on non-human minds has, naturally, focused on animals—apes, dogs, whales, bats. Some have considered other branches of the tree of life, too—cephalopods, say, or insects. But, just over the past few decades, some brave scientists and philosophers have begun to look even further. They’re starting to ask whether concepts like planning, memory, and awareness may also extend beyond animals, into an entirely different kingdom of life. They’re starting to take seriously the minds of plants. 

My guests today are Paco Calvo and Natalie Lawrence. Paco is director of the Minimal Intelligence Lab at the University of Murcia in Spain and one of the leading figures in the new science of plant intelligence. Natalie is a writer, illustrator, and historian of science based in London. Paco and Natalie are the authors a new book, Planta Sapiens. In it, they make the case that plants—though so often treated as an inert backdrop—are, in fact, cognitive creatures. Albeit creatures of a very different sort. 

In this conversation, we talk about the fact that plants are so often ignored, by both lay people and scientists alike, and consider some of the reasons why this may be. We discuss some spectacular phenomena that have recently come to light about plants—how they respond to anesthesia, how they mimic other plants’ leaves, how they seem to be able to “see” their surroundings. We talk about the question of whether certain plants have evolved to be more cognitively sophisticated than others. We consider the fact that plants and animals rely on the very same neurotransmitters and traffic in the same sort of electrical signaling. We also touch on wild versus domesticated plants, Charles Darwin’s root-brain hypothesis, plant sensing as akin to echolocation, the power and dangers of time-lapse photography, and the question of whether plants have inner experience.

Plants are super cool in themselves. Honestly, some of the stuff we discuss in this episode—if you’ve never heard it before—will kind of blow your mind. But plants are also more than that: they're a prism through which to examine some of the biggest questions about intelligence and cognition. Questions like: What are the minimal requirements for conscious experience? Are brains necessary for thinking? Can we truly compare the cognitive abilities of very different species? And should we? 

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Alright friends, without further ado, on to my conversation with Paco Calvo and Natalie Lawrence. Enjoy!

A transcript of this episode is available here.

Notes and links

3:00 – For a popular overview of research on the mimicking plant, Boquila trifoliata, see here. The recent study testing whether this plant can also mimic unfamiliar (plastic!) plants, see here. 

20:00 – The focus on climbing plants began at least as early as Charles Darwin—see his 1875 book, On the Movements and Habits of Climbing Plants. 

24:30 – For discussion of domestication and how it affects the behavior, physiology, and cognition of animals, see our earlier episode with Brian Hare.

25:00 – Darwin introduced the term “circumnutation” in his 1880 book, The Power of Movement in Plants.

28:00 – The original paper in which the idea of “plant blindness” was introduced. Since this term was coined, a wealth of research has looked at the underpinnings and consequences of “plant blindness,” and has tested interventions that might mitigate it (e.g., here).  

39:00 – A study investigating the effects of anesthetic drugs on several plants, including Venus Fly Traps.

44:00 – A recent article reviewing what we know about neurotransmitters in plants.

51:00 – A very brief overview of the vascular system of plants. 

53:00 – Our audio essay on Darwin’s “root-brain hypothesis” (or read here). 

57:00 – A recent study on peas reaching toward support poles, suggesting they are able to “see” those supports.

1:00:00 – A study examining “skototropic” behavior in a tropical vine.

1:03:00 – A recent paper by Dr. Calvo and a colleague on the question of plant sentience. Skeptical discussions of the idea of plant sentience can be found here and here.  

Paco Calvo recommends:

The Sentient Cell (forthcoming), by František Baluška and colleagues

White Holes, by Carlo Rivelli

Natalie Lawrence recommends:

Other Minds, by Peter Godfrey-Smith

Many Minds is a project of the Diverse Intelligences Summer Institute, which is made possible by a generous grant from the Templeton World Charity Foundation to UCLA. It is hosted and produced by Kensy Cooperrider, with help from Assistant Producer Urte Laukaityte and with creative support from DISI Directors Erica Cartmill and Jacob Foster. Our artwork is by Ben Oldroyd. Our transcripts are created by Sarah Dopierala.

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