The Interdependence of Irrelevant Alternatives

I don’t understand psychology. I’ve never studied it formally, and have read only a few popular books written by psychologists (e.g. Daniel Gilbert’s excellent Stumbling on Happiness). Not understanding psychology is one of the reasons I like being a sociologist – our explanations act on a different level, a level I feel more comfortable with (although at times it’s awkward to avoid a bit of psychologizing). When I’m trying to understand microeconomics and its critiques, however, I have to engage a bit more with that kind of work – rationality, what that means, deviations from it, the whole behavioral turn in economics. One of my favorite “deviations” is the violation of the axiom of “independence of irrelevant alternatives” (IIA). IIA says that if you prefer A to B when you don’t have option C, then you will still prefer A to B when you do have option C. So, if you have a choice between salad and soup and you choose soup, and then the waiter says, “But wait, you could also have fries!” you won’t then decide to have the salad. There’s some experimental work that shows people do precisely this (although not particularly often, if I recall correctly) but I’d never really encountered it in my own life…

Until tonight. As a bit of back story, in undergrad I spent a lot of time wishing I had more to do on Saturday nights. My first year, I didn’t meet a lot of people except through my older siblings, and for some reason I was never involved in their Saturday activities (perhaps because I didn’t really drink then, or go to bars). So I’d always end up in my dorm, failing to get work done, and mindlessly clicking away at some video game. I’m sure most of us have nights like that – where you don’t have anything to do, but wish you did, and can’t get anything done because of it. Things have improved in the last few years, and tonight (a Tuesday!) many of my friends gathered at our usual pub – affectionately nicknamed the Winchester. I realized early on that I just wasn’t feeling it (getting over a cold, didn’t sleep much, etc.), and decided to head home early to read a good book. What’s fascinating (to me anyway) is that the existence of the option to go out makes me feel completely differently about staying home. Even though, tonight, I prefer home to going out, the possibility of being out and actively electing the opposite means that I will likely get much more done and be happier doing it (much as I would have probably elected to stay home rather than going to a frat party or a skeezy bar freshman year). It’s not a perfect example, as there are only two choices involved and the second choice is changing the value of the first not the choice elected, but I think it fits the general idea.

Speaking of which, I should go read. And sleep. And get over this expletive deleted cold.

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  1. Mark K.

     /  June 17, 2009

    So, if you have a choice between salad and soup and you choose soup, and then the waiter says, “But wait, you could also have fries!” you won’t then decide to have the salad.

    I do this. Thinking of the fries might make me say “ugh, hot food actually doesn’t sound so good” or “wait, that soup might be salty after all, bleh” or something. And then I pick the salad.

  2. Colds are going around. Mine’s just settling nicely into my chest. Joy.

    Around my school the students often run fundraisers where they get a bunch of Krispy Kreme donuts, throw in some home-baked cookies or muffins or something, and wonder why they have trouble unloading this fatty/sweet glop on their neurotically weight-conscious professors.

    The donuts are right out, because they engage an instant defense, and although the muffins might be dietetically acceptable they’re a bit scary and unappealing. So the choice is B but unit sales suffer.

    I tell the kids they need to offer C, a couple of baggies with celery and carrot sticks, not because anyone will actually buy them, but because they’ll break the plausibility seal and get the marks bellied up to the table, at which point the Krispy Kremes ooze back into play and do their nefarious work. I actually talked the marketing club into doing this and they thank me every time they see me.

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