I think its pretty clear that there is no consensus on the definition of intelligence. And we need to remember that the original IQ test was developed at the beginning of the 20th century in France, not to define intelligence, but to identify children who are slow learners in school. Now, many of the modern definitions of intelligence all include some level of multiple intelligences. Now, I am not a psychologist. I don't have training in psychology, but I just want to go over this very briefly, because I think it's important for us, if we're gonna try to define plant intelligence to understand what we think about intelligence in humans. So one of the very popular theories of multiple intelligences said that humans have three types of intelligence. Analytical intelligence. This might be the type of intelligence that we classically think of IQ tests, mathematical ability. Creative intelligence, and what's termed practical intelligence, the ability to know how to do things. Other models further refine this and add in two other types of intelligence. Emotional intelligence, which has gotten a fair amount of press over the past number of years, and social intelligence. The well-known psychologist, Howard Gardner, has expanded this even further to where he as nine different types of intelligences. So, theoretically, why not add a tenth level of intelligence and we can define this as vegetal intelligence. Plants clearly don't have social or analytical intelligence but maybe there is a plant type of intelligence. But even if we could define a vegetal intelligence, does this really help us understand plant biology? Maybe the question shouldn't be whether plants are intelligent, but rather plants are aware. As I hope I've convinced you in this course, plants are acutely aware of the world around them. They are aware of their visual environment. They differentiate between red, blue, far red and UV lights and respond accordingly. They are aware of the aromas surrounding them and respond to minute quantities of volatile compounds wafting in the air. Plants know when they're being touched. They are aware of gravity. They can change their shapes to ensure that their shoots grow up and that their roots grow down. And plants are aware of their past. They remember past infections, and the conditions they've weathered, and then modify their current physiology based on these memories. Now I have a confession. I did not want to call my book What a Plant Knows. This was a title that was actually suggested to me. My original response to this title was not too dissimilar from what many of you have written in the forums, but plants don't know anything. But whether plants know or not is, I think, less important than what we know what we're talking about. Whether or not plants know, I hope I've convinced you that plants are infinitely complex. Rather than immobile, maybe even stupid objects, I hope you now have a greater appreciation for the sophisticated sensory machinery that powers a plant and enables it to survive in every changing condition. Enables it to literally weather a storm. But is important for us to remember plants are not aware of us as individuals. We are simply one of the many external pressures that increase or decrease a plant's chances for survival and reproductive success. A plant is aware of its environment, and indeed people are part of this environment. But plants are not aware of the gardeners or scientists who develop what they consider to be personal relationships with their plants. While these relationships may be meaningful for us, as a caretaker, they are not dissimilar to a child and her imaginary friend. The meaning is unidirectional. And I say this as someone who has more than once used anthropomorphic language in the lab with sentences such as, these mutant plants don't look so happy today. Terms such as happy are our own subjective assessment of a plant's decidedly unemotional physiological status. For all the rich sensory input that plants and people perceive, plant senses are not manifested in emotion. That probably is one of the things that defines us as humans. We project on plants our own emotional interpretations and assume that a flower blooming is happier than one that is wilting. Well, if happy can be defined as an optimal physiological state, then perhaps this term fits. But I think that for all of us, happy depends on much more than being in perfect physical health. Actually, I think we've all known people who are afflicted with various ailments who consider themselves happy, or otherwise, very healthy individuals who are actually miserable in their own mood. Happiness, I hope we can agree, is a state of mind. So if humans and plants are similar in that both are aware of complex light environments, intricate aromas, different physical stimulations, if humans and plants both have preferences, and if both remember, then do we see ourselves when we're looking at the plant? What we must see, I think, is that on a broad level, we share biology, not only with chimpanzees, and with dogs, but also with begonias and sequoias. We should see a very long lost cousin when we gaze at our rose bush in full bloom knowing that we can discern complex environments just as it can. Knowing that we both share common genes. When we look at ivy clinging to a wall, we are looking at what, save for some ancient stochastic event, could have been our own fate. We are, as I hope you’ve learned in this class, seeing another possible outcome of our own evolution, one that branched off some two billion years ago. As we come to the end of our class, I wanna finish by reading the last two paragraphs of our textbook, which sums up my own personal take on what a plant knows. A shared genetic past does not negate eons of separate evolution. While plants and humans maintain parallel abilities to sense and be aware of the physical world, the independent paths of evolution have led to a uniquely human capacity, beyond intelligence, that plants don't have, the ability to care. So the next time you find yourself on a stroll through a park, take a second to ask yourself, what does the dandelion in the lawn see? What does the grass smell? Touch the leaves of an oak, knowing that the tree will remember that it was touched. But it won't remember you. You, on the other hand, can remember this particular tree and carry the memory of it with you forever. And now if you'll bear with me a little bit more, if you want, you can come with me on a tour of my lab and learn a little bit about my research.