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## Why Transitivity Violations Can Be Rational169

ananyo writes "Organisms, including humans, are often assumed to be hard-wired by evolution to try to make optimal decisions, to the best of their knowledge. Ranking choices consistently — for example, in selecting food sources — would seem to be one aspect of such rationality. If A is preferred over B, and B over C, then surely A should be selected when the options are just A and C? This seemingly logical ordering of preferences is called transitivity. Furthermore, if A is preferred when both B and C are available, then A should 'rationally' remain the first choice when only A and B are at hand ... But sometimes animals do not display such logic. For example, honeybees and gray jays have been seen to violate the Independence of Irrational Alternatives, and so have hummingbirds ... Researchers have now used a theoretical model to show that, in fact, violations of transitivity can sometimes be the best choice (original paper) for the given situation, and therefore rational. The key is that the various choices might appear or disappear in the future. Then the decision becomes more complicated than a simple, fixed ranking of preferences. So while these choices look irrational, they aren't necessarily."
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## Why Transitivity Violations Can Be Rational

• #### Transisviviisiity (Score:1)

by Anonymous Coward

I'm sure the word "transitivity" feels rather violated by that ridiculously bad misspelling in the headline.

In other news: My security word is "fellatio." Just thought you'd all like to know.

• #### Re: (Score:1)

I'm with that one guy who said we retitle the "editors" as "word rapists." Although lately the summaries have been slightly less egregiously misleading than usual.

• #### Code monkey like tab AND mountain dew (Score:2)

So basically, they discovered that humans aren't the only animals that enjoy variety in their diet?
• #### Re: (Score:2)

So basically, they discovered that humans aren't the only animals that enjoy variety in their diet?

That, and/or they discovered that humans aren't the only ones who make decisions that seem unreasonable and arbitrary to a third party observer.

TL;DR version:

They discovered that humans are animals.

• #### Re: (Score:2)

That, and/or they discovered that humans aren't the only ones who make decisions that seem unreasonable and arbitrary to a third party observer.

Such as drinking crap like Tab or Mountain Dew. It may give you kidney stones, do a poor job of hydrating, lack vital nutrients, and only contain monomers which provide nothing more than short term energy, but it tastes sooo good.

• #### Re: (Score:2)

Yesterday I tried to let my dog lick my cereal bowl; he sniffed it, turned away, and promptly began licking his backside.

I'm not really sure I want to know what makes a dog ass more appealing than a bowl of Kix...

• #### Re: (Score:2)

I don't think "enjoying" is something they can easily determined in honeybees or birds. They basically hypothesized that choices can be made based on future availability rather than just current state (i.e. "wow, animals can think!").

Or to put it in your terms: even if you didn't particularly like Twinkies, you may have hoarded them right before Hostess went bankrupt since you didn't know if you'd ever get another chance.

• #### Finally some sense to being dumb (Score:1)

This will be the perfect excuse for every situation the human being can't explain his moral decisions, like why do we act stupid when in love, why do some people chose to go to war and why did they sack Conan from the Tonight Show.

• #### Mood (Score:2)

There's just randomness in decision making sometimes. Get over it. Sometimes I just feel like stuffing my face with cheap pizza. Other times I prefer to skip dinner entirely.

• #### Re: (Score:2)

Maybe, although you're consciously unaware of it, your body craves the carbohydrates, proteins, and lipids that cheap pizza provides. And then other times, despite the fact that it's dinner time, you had a late lunch and you don't currently need any energy input, especially considering that you haven't used much energy sitting around browsing Slashdot.

There may be randomness in decision making sometimes, but basing a decision off of 'this is what I feel like' isn't random, you're just not making a conscious

• #### Based on what? (Score:4, Insightful)

on Wednesday January 15, 2014 @11:25AM (#45965323) Homepage

Organisms, including humans, are often assumed to be hard-wired by evolution to try to make optimal decisions, to the best of their knowledge.

What about humans have we seen to suggest humans are rational or are hard-wired make 'optimal' choices?

For biologists (or economists) to make this assumption has always struck me as terribly flawed, because in the real world, we see quite the opposite.

In the case of humans, cultural biases and any number of things skew our decision making to be less than perfect. And any theoretical model which assumes otherwise is pretty much the equivalent of assuming a perfectly spherical cow.

• #### Re: (Score:1)

TFA is badly written in this sense that so called irational is in fact not the way choices are made but our thinking about the choices themselves as it is apparently detached from the past and future. As in example they gave: if you usually have preference a b,c etc then in situation when different combinations are presented choices are still to be made consistently but apparent choices are not and the reason is not that the animal is less consistent but that the preference is not absolute but depends on th

• #### Re: (Score:1)

by Anonymous Coward

There are basically two reasons for this.

One reason is that a rational actor is simple to model, as is the completely irrational actor. Altruistic is also fairly easy. Other models are tricky to define, let alone use.

The second reason is that the deviation from rationality may often be viewed as a stochastic variable with zero mean. Ignoring it affects individual cases, but not the overall conclusions.

But in this case, it seems that there are two ranking functions at play. There's the instant ranking: (if I

• #### Re: (Score:3)

The second reason is that the deviation from rationality may often be viewed as a stochastic variable with zero mean. Ignoring it affects individual cases, but not the overall conclusions.

What is interesting about current research [nytimes.com] is that this assumption appears to not be true a lot of the time.

• #### Re: (Score:2)

In the case of humans, cultural biases and any number of things skew our decision making to be less than perfect. And any theoretical model which assumes otherwise is pretty much the equivalent of assuming a perfectly spherical cow.

Hell, if you have two models of product, say, A and C, where A is better and more expensive than C, introducing a mid-range product B can skew sales towards A. I.e., if you have A and C, C sells more (generally because it's cheaper), but by having B, you can drive sales towards A

• #### Just because (Score:2)

A is better than B and B is better than C doesn't automatically mean A is better than C.

It would require more details and specifics.

When A and B are compared, the criteria that make A better than B doesn't necessarily make A better than C. The specifics and criteria used to judge/choose "better/preferred" need to be known as well.

Silly (and highly personal example):
A = Reese Peanut Butter Cups
B = M&Ms
C = Reese's Pieces

I like A more than B, and B more than C, but given the choice between A and C, I'd pi

• #### serious omissions in the reading (Score:1)

Its important to reinforce the fact that violations in transivity, while rational, may never be appropriate under some circumstances.

in a TSA checkpoint. is your transivity under 3 ounces? did you remove your A and B before walking through C?
if you clicked through the EULA for windows 8 without reading, boy will you ever be sorry. You cant violate transivity or Internet explorer will res
• #### Re: (Score:2)

But the TSA is a Travesty, not a "transivity"....

• #### News at 11 (Score:2)

Real life more complicated that contrived mathematical / logical model.

• #### Re: (Score:2)

More like "world defies 'common sense' solutions to problems", Which is amusing because you phrased it as one of those "common sense tells me this is obvious" type rejoinders.

• #### Re: (Score:2)

I just like pointing out that "Common Sense" is what tells you to put out a grease fire with water and steer your car out of a skid.

• #### Re: (Score:2)

Yep. Bad news for theoretical economics, which depends heavily on the assumption of transitivity or equivalent properties.
• #### Maybe... (Score:2)

Without it, humans would have a heck of a time with rock, paper, scissors.

• #### Re: (Score:2)

Good old reliable rock. Nothing beats rock.

• #### Totally flawed model (Score:5, Insightful)

on Wednesday January 15, 2014 @12:01PM (#45965749) Homepage

If you're trying to find a balanced diet using many ingredients and take one of those away, the rest of the diet might change totally. For example, let's assume the removed ingredient was a very good source of protein. Now you're scrambling to replace it with other protein sources, introducing foods you didn't need before. And now you're high on carbs, so your high-carb food goes out and is replaced by something else, so now you lack vitamin D so we add another new food and so on. It's a set ordering not a factor ordering because if you've eaten beef all week you'd rather eat pork, even if you prefer beef.

• #### Re: (Score:2)

It seems like a resource optimization [wikipedia.org] problem, albeit a very difficult one to model.
• #### Re: (Score:2)

They don't claim to have a realistic model of the situation: They showed a very simple model in which the rational behavior contains an apparent violation of transitivity. And they didn't need to introduce a variety of nutrients to obtain it. This makes their model better, in the sense that it is simpler.

[Sorry, I posted as AC earlier.]

• #### This explains why people order a McRib ;^p (Score:2)

I always wondered why people ordered McRibs.

It certainly can't be consistently ranked better than anything else on McD's normal menu, yet people seem to irrationally still buy them.

Maybe this explains it... Nah... ;^P

• #### Predators (Score:3)

<.oc.puslla. .ta. ... aitram.elytsoom.> on Wednesday January 15, 2014 @02:30PM (#45967737) Homepage Journal
Unpredictability is a necessary trait when evading predators, so an organism that always chose C when C > B and B > A would be more predictable and easier for an intelligent predator to catch.  This tendency not to would need to be deeply hardwired into the nature of the organism, since otherwise it would rarely kick in and, again, the organism would be easy prey.  Optimising a small subset of a problem (and the whole problem is survival and procreation) often leads to locally optimal yet seriously globally subobtimal solutions.  The greedy algorithm works on only a few cases (sometimes called monoids if I remember my combinatorial optimisation text, though that was over a decade ago); and with only slightly more complex problems it is often easy to construct pathological cases where the greedy algorithm gets it wrong.  I see this result about organisms as another example of the principle that straightforward rational solutions are only the best when the problem is straightforward and simple.
• #### duh (Score:2)

In other news, there is more than one dimension!

• #### Path dependent decision making. (Score:2)

Evolution happens without any intentional action by the participants. The proto-eagle did not decide, "it is getting too crowded in this niche, let me fly higher, evolve keener eye-sight, may be a second foeva, the current one is not good for distance over 1 mile, and become an eagle". Many million proto-eagles made many ad-hoc decisions, and the ones that happened to hit on the right strategy, over many thousand generations became eagle. What you learn from evolution is statistical result of millions of e
• #### Re: (Score:2)

Forget about Chuck Norris and Rajnikant, look at Bishnu Shrestha [badassoftheweek.com] instead.

• #### Re: (Score:2)

The Gurkhas are legendary. Thanks for the link.
• #### Simple summary (Score:2)

Scientist always thought that choices made by animals could be modeled using simple algorithms such as if A is preferred over B and B is preferred over C, then if A and C is offered the animal would choose A. When the animal being observed didn't choose A they declared a transitivity violation. What they have discovered is that there model was flawed and what goes into making one choice better than another is more involved than first thought. As such, there is not transitivity violation and the animals st

• #### Re: (Score:2)

And it's a bit like when you are eating - if you love roast beef with mashed potatoes and have had that every day for a month, then you would pick something else just to get a change as long as you know it's edible, you may even be willing to pick food that you usually avoid.

The point is that nature has provided some species the ability to get bored with a certain food to ensure that there is a variation in the intake of nourishment and avoid deficiencies and dependability on a certain source.

Species that l

• #### Reminds me of a math class I took (Score:2)

I had a prof who would take a vote on which day we would have our test. Once he gave us the choice of next week monday or friday. The vote was overwhelmingly monday (I can't remember but something like 2/3). Immediately after he realized that wednesday was also an option, so we had a re-vote. Friday won out with a majority (not plurality) vote.
So, no, I don't think that guans are wired for logical decision making. Animals, I still hold out hope for.

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