Wednesday, August 26, 2009

Do ants think?

A paper in the August PLoS ONE (Ants, Cataglyphis cursor, Use Precisely Directed Rescue Behavior to Free Entrapped Relatives, Nowbarhari et al.) reports rescue behavior in ants. That is, they actively attempt to save an entrapped ant by digging around it and pulling on its limbs. Previous reports of ant digging behavior have been dismissed as an alarm response rather than rescue, but the authors of this paper beg to differ.

For this study, the researchers exposed study ants to six different situations, as described here.
Using a novel experimental technique that binds victims experimentally, we observed the behavior of separate, randomly chosen groups of 5 C. cursor nestmates under one of six conditions. In five of these conditions, a test stimulus (the “victim”) was ensnared with nylon thread and held partially beneath the sand. The test stimulus was either (1) an individual from the same colony; (2) an individual from a different colony of C cursor; (3) an ant from a different ant species; (4) a common prey item; or, (5) a motionless (chilled) nestmate. In the final condition, the test stimulus (6) consisted of the empty snare apparatus.
Only active nestmates, ants from the same colony, elicited rescue behavior. Others evoked aggression or no reaction. The authors conclude that a struggling nestmate emits a colony-specific pheromone to which rescuing ants respond.
Moreover, C. cursor ants are able to engage in highly precise behavior directed toward the inanimate object that has entrapped their nestmate. Thus, our findings show that rescuers somehow were able to recognize what, exactly, held their relative in place and direct their behavior to that object in particular, demonstrating that rescue behavior is far more exact, sophisticated and complexly organized than previously observed. That is, limb pulling and digging behavior could be released directly by a chemical call for help and thus result from a relatively simple mechanism. However, it's difficult to see how this same simple releasing mechanism could guide rescuers to the precise location of the nylon thread, and enable them to target their bites to the thread itself.
It's the last sentence of this paragraph that interests us. The thread is obviously not emitting any chemical signal, and the ants are not 'pre-programmed' to know that danger is connect to the thread, and that they could break it with their pincers. Anyone who has observed ants for any time at all, including Darwin, must surely be impressed by their sophisticated cognitive, decision-making abilities. They work together to move barriers from their trails, they figure out ways around barriers they can't move, they cooperate to bring prey back to the nest, and so on.

Darwin himself said it very well in Descent of Man (1871):
...the wonderfully diversified instincts, mental powers, and affections of ants are notorious, yet their cerebral ganglia are not so large as the quarter of a pin's head. Under this view, the brain of an ant is one of the most marvelous atoms of matter in the world, perhaps more so than the brain of man.

It's easy to dismiss the rescue behaviors described in this PLoS paper as 'only' biochemical. But cognition and sophisticated decision-making are evolutionarily ancient. And, what are they, really, but the interaction of complex surface molecules and their receptors? We tend to privilege human thought capabilities, but in fact our brains are just signals, ligands and surface receptors, too.

3 comments:

Mong H Tan, PhD said...

RE: Do or can ants think? -- Hardly!

It's easy to dismiss the rescue behaviors described in this PLoS paper as 'only' biochemical. But cognition and sophisticated decision-making are evolutionarily ancient. And, what are they, really, but the interaction of complex surface molecules and their receptors? We tend to privilege human thought capabilities, but in fact our brains are just signals, ligands and surface receptors, too.

I think your conclusion above has committed a common and persistent fallacy of the neo-Darwinist reductionism of “sociobiology” and of “consciousness” and of “evolutionism” (since the 1970s) that I recently commented here: “The nail in the coffin for group selection? -- RE: Not yet!” (NatureUK; May 29) and here: “The unnatural selection of consciousness -- RE: Commentary on Tallis' understanding of consciousness!?” (PhilosophyPressUK; August 14).

Briefly, our human cognition, memory, and sophisticated thought capabilities are not evolutionary relics, that could be defined by the classical Darwinism; nor predicted by the neo-Darwinist reductionism: the modern geneticism or selectionism which essentially and selectively denies or ignores “consciousness” mechanisms in humans at all, by simply reducing all that of “our brains [that] are [composed of] signals, ligands and surface receptors, [etc]” to those of “nothingness” or of mindless “meme” -- or of ant’s as Darwin had also exaggerated it in1871, by comparing it to “the brain of an ant [that] is one of the most marvelous atoms of matter in the world, perhaps more so than the brain of man”!?

Whereas unbeknownst to Darwin of the time and especially to the self-denial reductionism of the neo-Darwinists of the 20th century, modern neurosciences have shown that our brain and neurochemistry are (in fact) evolutionarily -- both physiologically and biologically -- far more complex and complicated than those of an ant’s; as ants are definitely devoid of those complicated cognitive and memory and thought mechanisms (like ours) at all; and ant behaviorisms are purely reactionary (or instinctive) and ants will respond only to their each species-specific pheromones, that only ants produce in nature, and in living, for their own survival and communications!?

Furthermore, only humans will survive and respond to the world by our both subconscious reactions (or intuitions) and conscious actions: the unique human capabilities of inventiveness and creativity that have had all spawn out of and from our existential memories and forethoughts of visions, or of imaginations, or of experiences and consequences, etc; and all these are the consciousness and conscience and the analytical traits and mental inheritances, that have had so distinguished, and separated us humans (or civilizations that we built) from ants (or colonies that they built) and other organisms (with their each own respective behaviorisms) since over 50 thousand years ago on this unique planet Earth!?

Thus, in your conclusion above: Are you implying that humans should behave like ants!? Or ants could think (and empathize) like humans!?

Best wishes, Mong 9/1/9usct10:39a; practical science-philosophy critic; author "Decoding Scientism" and "Consciousness & the Subconscious" (works in progress since July 2007), "Gods, Genes, Conscience" (2006: http://www.iuniverse.com/bookstore/book_detail.asp?isbn=0595379907 ) and "Gods, Genes, Conscience: Global Dialogues Now" (blogging avidly since 2006: http://www2.blogger.com/profile/18303146609950569778 ).

Anne Buchanan said...

Thanks for your comment, Mong. Our point is not to diminish human consciousness or thought, but that complex traits like these don't spring from nowhere. Like our limbs, immune system, teeth, and all our other complex traits, the human mind evolved from earlier forms. To us at least, there's no reason to assume that the ant brain doesn't share some of that complexity.

Ken Weiss said...

I think the issue here is perhaps what one means by the word 'think'. I don't know how ants perceive the world, but they are far more capable than a view of them as highly hardwired in their behavior (or else we are more hardwired than is usually thought). Ants solve nontrivial problems. That they use neurotransmitters and other chemicals, signals, and so on to do it does not take away from their abilities. We use such things, too.

Of course our type of thinking defines what we usually mean by 'think' and mainly involves our conscious lives. But we do much cognition and problem solving without, or before, cognition occurs. But we tend to equate 'think' with consciousness.

We are obviously different from ants, though we share neural signaling mechanisms etc. Of course, we should not 'behave like ants'! We should and must behave like people. Our divergence from ants is so ancient that our perceived worlds must be very different and so must our sense of awareness be.

I don't understand your comments about relics or neodarwinism etc. We are, from everything known, related evolutionarily to ants. That doesn't make our thought only a recurrence of what they have, if that is what you were suggesting. But it did build on what our common ancestor had, and did that in each lineage in its own way.