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Do Plants Think? (scientificamerican.com)
68 points by rosser on Aug 26, 2012 | hide | past | web | favorite | 51 comments

One of the most amazing feat of plants regarding information processing is the way the leaves optimize the gas exchange process. They do this by opening and closing small gates known as stomata [0].

Each stoma integrate their local state with the current atmospheric conditions and the state of their neighbors, behaving as the cells of a cellular automaton [1].

Plant leaves literally compute.


[0] http://en.wikipedia.org/wiki/Stoma

[1] http://www.pnas.org/content/101/4/918.full

It's an interesting article, but the title is a bit misleading. The article is mostly about how plants react to various sensory stimuli.

"Any headline which ends in a question mark can be answered by the word 'no'". http://en.wikipedia.org/wiki/Betteridges_Law_of_Headlines

Don't take this personally, but can people please stop mentioning "Betteridge's Law"?

Somebody mentions it every single time a headline ends in a question mark, and it's not witty, clever, or funny any more. It's just annoying at this point. That style of headline isn't going away, and at this point everybody knows about "Betteridge's Law".

For those of us without flag powers, mentioning the adage is the most we can do about titles like these on HN. Of course I could just stop reading the HN front page, but that seems a rather null solution.

I've got flag powers, but I've basically given up. People have decided to upvote things that aren't relevant to this site, and by the time I see them, it's too late.

And reading the 'new' feed is even more discouraging. I can't deal with the constant flood of garbage that obviously wasn't interesting or relevant, just to find a few tiny morsels.

Don't give up! Flag, and comment (briefly) about why. It's been my experience that lots of storied that I believed were long past flaggable (80-90 upvotes) have been killed sometime after I flagged them.

Even if your flag doesn't kill the story, the conversation about why you flagged it will be valuable --- at the very least, more valuable than the off-topic story.

Leave better comments, then flag with abandon.

I did both of these. This resulted in the "flag" links disappearing.

Well, you've got me there. I flag frequently, like maybe 5-10 a day on average but sometimes 20+. Maybe there's another karma threshold or something I don't know about.

Actually, I didn't, and I found the comment entertaining. But I can see how it gets annoying after a few times.

Admittedly, "think" is perhaps an inapt word choice, but how is response to stimuli not, in some fashion, awareness?

Think of the "knee-jerk" reflex you get when the doctor hits you on the knee. It's a response to a stimulus, but it happens without even any involvement from your brain: it's just a round trip to the spinal cord.[1] I don't think that's what we usually think of as "awareness", which happens at the cognitive level. Reflexes like eye-blinking are even operational when you're unconscious.

[1] http://en.wikipedia.org/wiki/Patellar_reflex

Right. Questions like this are stupid because they're not asking a usable question. The best response to the headline is really, "Define a thought." This is difficult in humans, never mind anything else.

If you choose to define thoughts as stimuli-response, then you're classifying our entire system of instinctive responses as thoughts, which is practically a brain bypass. (The literal knee-jerk reaction.)

> Admittedly, "think" is perhaps an inapt word choice, but how is response to stimuli not, in some fashion, awareness?

Sure, it can be, if you're willing to admit that computers respond to stimuli.

As a vegetarian, I constantly have to suffer through idiotic arguments based on headlines like this. I know this happens in all areas of life, but this is definitely the one to which I am exposed most often and it drives me absolutely nuts.

Journalists, please stop giving people ammo for their stupid guns.

For the record, I agree with you.

BUT, as a biologist, I often find it amusing that people discount plants completely. It's easy to forget that they are alive too. Fundamentally, they aren't so different from you or a turtle or a fruit fly. Different cellular structure, sure. Not easily recognizable "consciousness", absolutely. Non-motile, check.

However, plants are very much alive. They react to stimuli, survive in hostile environments, procreate. They are more alien to our sensibilities, but they are arguably not very much different in the grand scale of things.

As another biologist, I like to troll vegetarians by insisting that plants have pain, because what else do you call a signalling system which starts a damage-response-system?

Also, plants are autotrophs. Cows are heterotrophs. By some inverse of the categorical imperative, you should not do to beings what they are not doing to others. I.e. don't eat the autotrophs. Eat the heterotrophs.

Usually the line is not drawn around "ability to feel pain", it's drawn around "has a central nervous system", which is used as a rough proxy for "is sentient". Otherwise it would be OK for a vegan to kill and eat a person who has lost the ability to feel pain, but otherwise functions normally.

Edit: came along this interesting link about the measure of sentience: http://en.wikipedia.org/wiki/Sentience_quotient

Cool link! And I heard that argument before in my trolling attempts - usually I answer like this:

A central nervous system is defined as "the complex of nerve tissues that controls the activities of the body". Plants don't have "proper" animal nerve tissues, but they do have a complex system that controls activities of the plant, by sending mRNA/proteins through the phloem to the parts of the plant that need regulation (a lot of it is local regulation but psssst, this kills the trolling)

Nice link! Never heard of that before. But if (non-conscious) IBM Watson has a quotient of +12, and humans have one of +13, what good is it for?

That's just playing off the terrible definition we have of "pain"

I dated a vegetarian for a while and people would always ask her dumb questions about it and make unoriginal (basically exact same) jokes about it so I sympathize with you to a degree.

On the other hand, I find it annoying that a vegetarian can draw the line in the sand and decide what is morally correct for everyone to believe.

I'm sure there are vegans judging you for eating (milk, eggs etc. whatever you do eat), and there are "vegetarians" that eat seafood who think you are too extreme, and there are probably people who only eat plants that died of natural causes who think all those groups are terrible and should have more self control over their diet.

The article was pretty interesting and novel to me and if you get a few more dumb questions from people, I don't think it is the end of the world.

On the other hand, I find it annoying that a vegetarian can draw the line in the sand and decide what is morally correct for everyone to believe.

Pretty much everyone does that. People don't notice so much when other people are drawing the same lines as them.

I find it annoying that a vegetarian can draw the line in the sand and decide what is morally correct for everyone to believe.

Only some vegetarians do that, and it's wrong to imply that it's a defining feature of the demographic. I have vegetarian friends that cook me meat when I visit for dinner, despite me asking not to get special treatment. Other vegetarians just don't like the taste of meat, nothing to do with moral or health attitudes.

Unless the vegetarian is being vocal about the moral issue, it's pretty impolite to bring up the topic apropos of nothing - it's almost always just the questioner trying to score some sort of point.

Full disclosure: I'm a vegetarian. Another bonus of this choice is health. My wife and I made it through various third world countries without food poisoning as the travelers around us fell Ill. It could be coincidence, but considering that it was the only dietary difference, I doubt it. Well cooked vegetables only. It's worth considering when food safety is an issue.

Completely agree, but also a terrible tragedy for those times when you end up in Spain, Italy, France, Japan, and other countries with amazing food and good-to-great hygiene.

That said, I eat vegetarian most of the time because the alternative is to eat scary meat, which I'm not going to do. It's insensitive to the animal and a serious risk for me. Accordingly, I haven't eaten fast food in over a decade.

I'm also going to Spain next month and have every intention of gorging myself on delicious cured pork products every chance I get.

I'm sorry, what's scary meat?

My instant thought is backstreet barbequed guinea pig that's been on a warmer for days, with people picking thir choice with bare hands. Peru has amazing vegetarian food luckily!

The meat you'll find at a McDonalds, e.g.

Oh, ok. Well I barely consider that meat anyway ;) And I'm with you, I wouldn't eat it either.

> people who only eat plants that died of natural causes

Not that I've heard of. I have heard of fruititarians, who only eat the parts of plants the plants produce specifically to be eaten. (It's more complex than that, in fact, but I won't go into it all here.)


That Wikipedia article mentions that "According to author Adam Gollner, some fruitarians eat only fallen fruit."

Downvoted. It's a semi-serious article, not something that suggests you shouldn't eat plants (what else can you eat? meat? cows eat lots of plants when they are being raised).

Only a really disingenuous person would claim it's kinder to eat meat. There's arguments in favor of eating meat (there's some book called "The Mindful Carnivore" which goes a bit deeper than "meat bad veg good"), but ... that's way off topic.

Nobody with half a brain thinks plants scream when you eat them, and that's not what the article is saying.

There actually is a religion/practice that eschews even eating whole or root vegetables on the basis that killing plants is also murder. It's called Jainism, and practitioners eat only fruits, leaves, nuts, seeds, and the like. They also walk barefoot, and sweep the ground in front of themselves as they go to avoid inadvertently stepping on insects.

And in countries like India, the belief is neither considered outrageous nor is it hard to follow. In fact, Jain food is readily available and basically the same as typical Indian vegetarian food minus the root vegetables plus replacements. It is often hard to distinguish.

As a meat-eater, I've determined that the answer to the question isn't particularly relevant to my dietary choices.

Strangely, I've never had anyone argue this to me, but I do get asked, several times per year, if I eat seafood.

In many languages, "meat" roughly equates to "red meat". Fish and fowl are considered different categories. I believe this came about because of a Catholic church ruling that fish did not count against the promise to give up meat during Lent. It also lead to silliness like classing the chig├╝ire / capybara, basically a large swamp-dwelling gerbil, as a fish.

Not just the capybara, but beavers and muskrats too! It actually makes some sense when you consider that Thomas Aquinas' Aristotelianist classification of animals more to do with habitat as anatomy.

My usual answer: "Only Broccoli Fish."

When they ask what a Broccoli Fish is, I explain patiently that there's no such thing.

> if I eat seafood

Do you kill invasive insects? Frankly, a shrimp or a lobster is pretty much on a level with a cockroach, when you get down to neural complexity and everything relevant to moral vegetarianism, as opposed to vegetarianism for health reasons.

Bony fish are not much more complex.

Things like sea cucumber don't even have brains: They have nerves, but they lack any centralized structure for them to converge on. Same with jellyfish.

So I suppose my point is that it isn't a dumb question, at least if you're a vegetarian for moral reasons related to killing a living being with emotions.

You make a very good point, and if you excuse my snarkiness, I shall now describe myself as "an exclusive consumer of plant cells" instead of "vegetarian."

If you define 'feel pain' correctly, single-celled organisms have been observed to feel pain in that they move away from noxious chemicals.

What about the intensive questioning on how you get protein. I do t think I've every asked anyone anything like this. Is there anything more boring?

I particularly enjoyed the memory part - where they mention a venus fly trap remembers the contact with one leg of the insect then confirms that another leg has touched, and then the trap closes. Then 15-20 mins later it'd open again. This eliminates false positives, conserves energy!

while(1): if (get_count_contact()!=2) continue; else close_trap(); sleep(15); set_count_contact(0);

If nature wrote this kinda code, Evolution is like debugging! But this is really really oversimplified ...

I think (no pun intended) that plants and some other species that lack central brains operate more like BEAM robots http://en.wikipedia.org/wiki/BEAM_robotics in that the behaviors they exhibit can be remarkably similar to intentional behavior.

If you believe that a Turing test is sufficient to judge an AI as "intelligent" then in the same way you'd have to conclude that the behavior is the measure, which seems to disallow certain assumptions regarding intent.

Then again, given the recent research into how the gut flora can affect all manner of processes in humans, it certainly looks like Me(tm) is a product of a whole host of complex systems whose interactions display an emergent "intentional" system.

If Aliens visit us, they will likely classify us as "Non thinking creatures", just as we classify plants as non thinking. Everything rests on a spectrum and trying to classify everything into bins as "thinking" or "non thinking" is a childish way to go about explaining how the world works.

If you generate a 200 hz signal around the root systems of cabbage, the roots will grow toward the source. The plants can generate that signal as well, so yes, certain plants communicate with a very rudimentary audio communication system.

Do plants think? It depends on your definition, but yes, Plants think, computers think, humans think. A better word might be "plants calculate the best course of action to achieve a goal just like humans do.".

> If Aliens visit us, they will likely classify us as "Non thinking creatures"

No. Obviously not. We obviously manipulate our environment in complex ways.

> "plants calculate the best course of action to achieve a goal just like humans do.".

If you truly believed this you could never justify eating them.

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