Contradictory in studies about ants

[thinker_jeff]

Here is the classic conclusion for this topic.

 

Mindless Collectives Better at Rational Decision-Making Than Brainy Individuals

Humans often make irrational choices when faced with challenging decisions. Ant colonies, however, can make perfectly rational selections when confronted by tough dilemmas. This isn't because lone ants are especially knowledgeablethey're not. Instead, when ants are grouped together, a kind of "wisdom of the crowds" avoids the kind of mistakes that individuals can make, new research shows.

 

In terms of evolutionary biology, animals strive to maximize their fitness. Still, actions that seem counterproductive and irrational occur not only in human societies, but also all over the animal kingdom. For instance, when honeybees and hummingbirds have two equally tempting choices of nectar, a third alternative inferior to both can sway them to prefer one of the initial two options over the other. The animals apparently compare the inferior choice against the originals and conclude that one of the originals is better, even though nothing about them has changed.

 

Such irrationality can lead to deep insight, because "finding what makes the system fail can give a clue about how it works," explains Stephen Pratt, a behavioral ecologist at Arizona State University's School of Life Sciences in Tempe. Of special interest to Pratt is how groups of animals such as ant colonies make collective decisions. "We can even think of a colony as an analogue for a nervous systemby understanding how decisions emerge from interactions among ants in a colony, we may learn something about how decisions emerge from the interactions among neurons in a brain," he says.

 

To see if collectives behave rationally, Pratt and his student Susan Edwards investigated a common acorn ant of eastern North America, Temnothorax curvispinosus, which is tinya colony of 50 to 200 such ants can make its home inside a single nutshell. When their nest is damaged beyond repair, the ants choose their new home en masse. Scouts look for potential nests, and if enough of them close in on the same area, they then carry nest mates over.

 

The researchers made two artificial nests as potential homes. Nest A had a larger, less defensible entrance but a dark interior that suggested strong, thick walls, whereas nest B had a smaller entrance (more defensible) but a bright interior (weaker walls). As expected, when the researchers ran 26 ant colonies past these nests, the insects split roughly equally on the nests.

Then they provided inferior "decoy" nests to spur irrational choices. For instance, if they presented a decoy that was similar to nest B yet had an even brighter interior, the ants might irrationally prefer nest B over nest A, if past results with humans and animals are any guide.

 

Surprisingly, the decoys had no effect on the coloniesthey always made rational decisions.

 

"All minds, both collective and individual, have limited capacitythey have to use shortcuts and rules of thumb to solve difficult decision problems, and those shortcuts are expected to sometimes cause mistakes," Pratt says. "The ant colonies, however, were unfazed by a challenge that often elicits such mistakes in other animals."

 

So what makes these colonies so rational? Surprisingly, the very ignorance of the lone ants might be key. Instead of making comparisons between choices that can sway humans toward irrational decisions, individual ants typically know of just one option, which prevents them from making potentially misleading comparisons. Although the researchers expected the ants to behave irrationally, "we accidentally got a different insight about a possible advantage of collective cognition," says Pratt, whose findings appear today online in the Proceedings of the Royal Society B: Biological Sciences.

 

"We thought our brains and those of most animals could not always decide rationally because it was impossible to do so," notes behavioral ecologist Anna Dornhaus of the University of Arizona in Tucson, who did not participate in this study. "The ants show us that…there is a way to construct a decision-making system" that doesn't make irrational choices. The question then, she observes, is why our brains have evolved to act irrationally on occasion.

 

http://www.scientifi...decision-making

Now there is a new study about the behavior of ants.

Knowledgeable individuals lead collective decisions in ants

 

Self-organisation underlies many collective processes in large animal groups, where coordinated patterns and activities emerge at the group level from local interactions among its members. Although the importance of key individuals acting as effective leaders has recently been recognised in certain collective processes, it is widely believed that self-organised decisions are evenly shared among all or a subset of individuals acting as decision-makers, unless there are significant conflicts of interests among group members. Here, we show that certain individuals are disproportionately influential in self-organised decisions in a system where all individuals share the same interests: nest site selection by the ant Temnothorax albipennis. Workers that visited a good available nest site prior to emigration (the familiar nest) memorised its location, and later used this memory to navigate efficiently and find that nest faster than through random exploration. Additionally, these workers relied on their private information to expedite individual decisions about the familiar nest. This conferred a bias in favour of familiar nests over novel nests during emigrations. Informed workers were shown to have a significantly greater share in both recruitment and transport to the familiar nest than naïve workers. This suggests that they were the main determinants of the collective preference for familiar nests, and thus contributed greatly to enhance collective performance. Overall, these results indicate that self-organised decisions are not always evenly shared among decision-makers, even in systems where there are no conflicts of interest. Animal groups may instead benefit from well-informed, knowledgeable individuals acting as leaders in decisions.

 

http://jeb.biologist...cf-753fd3a881a5

Edited August 31, 2011 by thinker_jeff

[Maximilian]

I don't think the results are contradictory. The second study did challenge the assumption that multiple-choice decisions are evenly shared among the decision-makers in the colony, but this doesn't really affect the outcome of the first study.

 

The first paper "Rationality in collective decision-making by ant colonies" by Pratt et al. focused on one of the principles of rationality that is commonly violated by several animals, including humans.

A = B are perceived as equal. However, when C is added and it is dominated by one of them but not both, the one which dominates C is now preferred. In this case A, B and C were nesting sites. Here is the description of the nests;

 

"For ternary choices, colonies were given options A and B, as well as a third decoy nest, either D_A or D_B. Decoy D_A was dominated by A, but not by B; it had the same interior illumination as A (40 lux), but a larger, and thus less preferred, entrance size (9.5 mm diameter). It was not dominated by B because D_A had a darker, and thus more preferred, interior light level. Decoy D_B, on the other hand, was dominated by B, but not by A; it had the same entrance size as B (1.6 mm), but a brighter, and thus less preferred, light level (300 lux), achieved by fitting it with a transparent plastic sheet (Grafix Dura-lar) instead of a neutral-density filter. It was not dominated by A because D_B had a smaller, and thus more preferred, entrance size. "

What happens is that humans and other animals see the three options, and thus their judgement is affected by the decoy. But ants are not individuals who perceive the three of them and choose, the ants do a random search, find a nest, and recruit/transport. The better the nest is, the faster and more efficiently they recruit/transport. The first nest which gets to the quorum threshold will serve as the new nest for the colony. Because of this, the decoy can't affect their judgement. Aproximately the same amount of ants will arrive at A, B, and Da or b, however, the recruitment/transport towards A and B will be similar and higher than that of Da and b, so there is no irrational decission making.

In the second study, the researchers put a nest near the nest of the colony, marked the workers, and saw which workers explored the empty nest. This nest became the "familiar nest", because several workers had explored it. They induced emigration by destroying their current nest, and added a new nest which was just as good as the familiar nest but was "unfamiliar" to the workers.. The workers that had never been to the familiar nest explored randomly, and were as likely to find either nest. However, the worker ants with the "private knowlege" of the familiar nest would get to the familiar nest quicker and initiate recruitment/transport quicker. Thus, the worker ants with the private knowledge would contribute disproportionately in the decision making, making it more likely for the quorum threshold to be reached in the familiar nest first.

The findings from the second study did not come into play in the first study because the ants were not allowed to explore the surrounding nests before being induced to emigrate, and thus there were now knowledgable ants, only naïve ones.

Two interesting studies I can think of;

-Repeat the first study but let the ants explore the surrounding nests before inducing emigration.. Will more "knowledgeable" ants prefer whichever nest dominates the decoy?

-Repeat the second experiment but make the "unfamiliar" nest superior to the "familiar" one. Will the superior quality from the unfamiliar be enough to speed up the recruitment/transport to achieve the quorum threshold before the familiar one? For this experiment, different colonies should be exposed to the familiar nest during different amounts of time before inducing emigration.

This is my opinion. But it's late and I'm tired - so I could be very wrong

Anyway, thank you.

[thinker_jeff]

I like your opinion very much.

My question is more related to psychology. What kind of communication do ants have? Can an ant tell another what the nest looks like? Or, can it tell the comparison of two nests?

I assume that more information they can exchange, more rational choice will be made. Human beings can exchange information more than any other species, that why they dominate this world.

[jimmydasaint]

What an excellent and stimulating find. Well done. I have only read the first article up to this point and these are my thoughts on the mattter. The article is slightly misleading because humans have a much more complex set of decisions to make at any given time and (emotions, biochemistry and perception amongst other factors) dovetail in order for a decision to be made. Ants, on the other hand, seem to (unconsciously) prioritise a successful survival strategy and retain this 'collective' memory. Rationality and irrationality are value judgements that we make as humans on a type of behaviour. However, it is not human rationality being tested here but non-human behaviour, and I would be wary in ascribing human 'qualities to ants.

 

As to the point about communication, ants are sensate individuals and chemical communication is apparently a strong factor in adaptive behaviour.

 

It is probably safe to say that insects rely more heavily on chemical signals than on any other form of communication. These signals, often called semiochemicals or infochemicals, serve as a form of "language" that helps to mediate interactions between organisms. Insects may be highly sensitive to low concentrations of these chemicals -- in some cases, a few molecules may be enough to elicit a response.

Insect communication

Edited September 3, 2011 by jimmydasaint

[thinker_jeff]

What an excellent and stimulating find. Well done.

Thank you for the comment and I will keep doing that in SFN.

 

As to the point about communication, ants are sensate individuals and chemical communication is apparently a strong factor in adaptive behaviour.

There is still a question - can ants inform each other with a specific description about the nests? I think that makes a big difference to explain their behavior. We might not know the answer at this moment, however, it could help us to think of the further studies.

[Rhoops]

Would it unfair to ask how well the difference between 'rational' and 'irrational' decision making is known in humans first? Collectively for instance our societies make decisions , often for the greater good, more usually for that and a mixture of elite self interest, and less commonly entirely for the latter. This is not a political statement, simply pointing out that if social individuals, like primates are have at least 3 forms of collective organisation: group, group/individual, and individual based, I fail to see how its possible to extrapolate a simple dichotomy (and ignoring structural conflicting interests) in rational/irrational 'group as a unit' behaviour from a Eurykarote species so distant from us that isn't even a Deuterstome.

This sounds like a purely subjective analysis, where the answers are already pre-determined by the superficial anthropomorphism given to 'communal' 'social' ants.

Doesn't it strike you as a big 'coincidence' that some researchers from a species of rational/communal social monkies finds 'rationality/communality' issues in a species with no common ancestor with us for about half a billion years? Parallel evolution... fine, but don't cuddle up to it too much. The basic intellectual premise of these studies seems to me to be too Disney-esque

A little self awareness of how the question asking process is generated goes a long way in extending the length of one's linear logic chains...

[thinker_jeff]

Would it unfair to ask how well the difference between 'rational' and 'irrational' decision making is known in humans first? Collectively for instance our societies make decisions , often for the greater good, more usually for that and a mixture of elite self interest, and less commonly entirely for the latter. This is not a political statement, simply pointing out that if social individuals, like primates are have at least 3 forms of collective organisation: group, group/individual, and individual based, I fail to see how its possible to extrapolate a simple dichotomy (and ignoring structural conflicting interests) in rational/irrational 'group as a unit' behaviour from a Eurykarote species so distant from us that isn't even a Deuterstome.

This sounds like a purely subjective analysis, where the answers are already pre-determined by the superficial anthropomorphism given to 'communal' 'social' ants.

Doesn't it strike you as a big 'coincidence' that some researchers from a species of rational/communal social monkies finds 'rationality/communality' issues in a species with no common ancestor with us for about half a billion years? Parallel evolution... fine, but don't cuddle up to it too much. The basic intellectual premise of these studies seems to me to be too Disney-esque

A little self awareness of how the question asking process is generated goes a long way in extending the length of one's linear logic chains...

I had hard time to catch your point. For example: "This is not a political statement, simply pointing out that if social individuals, like primates are have at least 3 forms of collective organisation: group, group/individual, and individual based, I fail to see how its possible to extrapolate a simple dichotomy (and ignoring structural conflicting interests) in rational/irrational 'group as a unit' behaviour from a Eurykarote species so distant from us that isn't even a Deuterstome."

I don't want to be offensive. Maybe my English is not good enough.

[jimmydasaint]

Rationality and irrationality are value judgements that we make as humans on a type of behaviour. However, it is not human rationality being tested here but non-human behaviour, and I would be wary in ascribing human 'qualities to ants.

If I read the post correctly, he was re-iterating my point but in far more elegant, and emphatic, language than I could have used.