Biases are Fattening

In addition to all their other effects, biases can also contribute to obesity. Architectures of Control cite the story of how David Wallerstein discovered how unit bias could help sell more fast food. He observed how people were unwilling to buy two packages, but quite willing to buy a double-sized package. Hence the supersizing of everything.

Geier, Ronzin & Doros demonstrated that people tends to regard a unit of some entity is the appropriate and optimal amount by measuring how much people consumed free Tootsie Rolls or pretzels when provided in different sizes, or M&M’s provided with differently sized spoons. This likely explains why people tend to eat more when served larger portions. The authors suggest that the unit bias in food might be social: people don’t want to seem to be gluttons. Another possibility they suggest is that there is a culture-norm interaction: we package things in appropriate sizes, we learn the appropriate amount by being exposed to standard packages.

A third possibility is of course an aversion to wasting, whether instilled by mother or evolution. I have a fourth neurocognitive possibility: we run on hierarchical motor programs and tend to switch behavior when one of them has concluded. So consuming a unit would presumably be a single iteration of one such program. We can certainly learn more elaborate programs like "take unit; consume until full; leave the rest", but that requires ongoing monitoring that may be cumbersome or easily distracted. I would expect unit bias to generalise outside food too. The researchers point out that double features are rare but long movies are not, and that people take one ride on an amusement park ride regardless of whether it is 1 or 5 minutes long. I would also expect unit bias to tend to round our thinking towards the nearest integer number of convenient units.

Some months ago when I moved to the UK I made the deliberate decision to only buy Coca Cola in sixpacks rather than 1.5 l bottles. The result is that I consume much less, since I now only take a can instead of more or less continually refilling my glass. So clearly unit bias can be used to downregulate food intake too. It is just that there is no incentive for the food sellers to do it. Maybe one solution to obesity would be easier ways of dividing bought food into convenient smaller units?

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  • http://manufacturedgods.blogspot.com/ LP

    “So clearly unit bias can be used to downregulate food intake too.”

    This is the same principle behind buying a large-sized package of a snack food to save on cost, but then immediately divvying it up into snack-size baggies to provide better portion signalling. Several cookie/cracker manufacturers have taken to selling multi-packs of small bags, to target calorie-oriented shoppers.

  • Doug S.

    “people take one ride on an amusement park ride regardless of whether it is 1 or 5 minutes long”

    Well, are you going to stand in line twice?

  • Nathan Iver O’Sullivan

    “The authors suggest that the unit bias in food might be social: people don’t want to seem to be gluttons.”

    But people would not be seen to be gluttons for eating two half-size portions instead of one whole portion–unless the observers have the unit bias. In this interpretation, one does not need the unit bias in order to manifest its symptoms–he only needs to care about his social standing. Maybe some people have the unit bias while others act as if they do so as to fit in.

    “A third possibility is of course an aversion to wasting, whether instilled by mother or evolution. ”

    Where’s the evidence? According to The Economist’s recent Technology Quarterly, per capita municipal waste collected in America in 2005 was nearly one ton. Maybe you have a more specific form of wasting in mind (e.g. wasting in the presence of others), but you did not specify it.

    “Maybe one solution to obesity would be easier ways of dividing bought food into convenient smaller units?”

    This is probably not any easier than counting calories, which is also unit-based and which is a more precise response to obesity.

  • http://www.aleph.se Anders Sandberg

    Counting calories requires counting, not to mention dealing with statistical information. A sizeable fraction of people are bad at it. Dividing (say) a pre-sliced loaf of bread into smaller packets of slices that can be stored in the freezer only requires simple everyday motorics.

    As for wasting aversion, I think it is pretty common. I know my mother has it, and she has been trying to instill it in me. I see a lot of references to it on various blogs; e.g. look at http://goodmorningyesterday.blogspot.com/2007/05/another-story-our-mother-told-us-beggar.html
    – a nice story, very suitable for a scarce food society and a form of food that can be stored a long time, but pretty irrational as a food security strategy in modern Singapore.

    If we have evolved and learned not to waste food, then it may be selective. Looking at plate waste studies it seems that people leave more of the low-calorie vegetables and drinks and leave less of the high-calorie meat part of meals:
    http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=6619458&ordinalpos=12&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

    Another study seems to suggest that people either eat almost all on the plate or almost nothing,
    http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=7119320&ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum
    which seems to fit unit bias nicely.

  • Hopefully Anonymous

    A great and interesting post that lives up to the spirit of this blog, in my opinion. Anders, I think your posts are of unusually high quality for this blog (not an insult to the blog, but a compliment to you).

  • Hopefully Anonymous

    Waste aversion is a very real and annoying problem in an abundant society. A key part of a diet I did a couple years ago to lose 60 pounds was to happily throw away perfectly good food -often. If I bought excess food in weakness, I considered it to be a double loss (financial and healthwise) to eat it. So I rejoiced every time I was able to throw away that bag of chips I bought in weakness. Although I received frequent criticism from friends for that behavior.

  • Nathan Iver O’Sullivan

    Anders, which statistical information are you referring to?

    Of course waste aversion is common, but the evidence seems to indicate that it is not sufficient to explain widespread unit bias in food consumption.

  • http://profile.typekey.com/sentience/ Eliezer Yudkowsky

    As my (paternal) grandmother says, “Better to throw it out than throw it in.” If only I could remember that I am not a wastebasket.

  • http://agoraphilia.blogspot.com Glen Whitman

    “So clearly unit bias can be used to downregulate food intake too. It is just that there is no incentive for the food sellers to do it.”

    Not so! Just the other day, I saw my local supermarket was selling packs of 100-calorie mini-cans of Coca-Cola. And that’s just one example. Here’s an article on the subject:

    http://www.usatoday.com/money/industries/food/2006-04-12-portion-controlled-snacks_x.htm

  • TGGP

    “people take one ride on an amusement park ride regardless of whether it is 1 or 5 minutes long”

    Well, are you going to stand in line twice?

    Even more ridiculous, are you going to “waste” or “leave over” part of the ride by exiting before it comes to a complete stop!

  • http://www.aleph.se/ Anders Sandberg

    I was referring to the nutrient labels. Tabular information is “statistical information” to most people. A surprising number of people have a hard time extracting the relevant information from even a simple table.

    The amusement ride example from the paper is indeed rather bad when you start thinking about it. But that doesn’t make unit bias irrelevant. Most people seem to settle for one iteration of the bumper car ride even when there is no queue and they can get out if they wish.

    And thank you, Hopefully Anonymous. I’m glad that I can contribute something.

  • http://profile.typekey.com/andrewgelman/ Andrew

    This reminds me of an insight I had several years ago which I used to tell the students in my decision analysis classes. They were always skeptical but maybe now with research behind me on this, they’ll believe me.

    Anyway, here goes:

    When I was younger, people used to complain about candy bars getting smaller and smaller. (For example, Stephen Jay Gould has a graph in one of his books showing the size of the standard Hershey bar declining from 2 ounces in 1965 gradually down to 1.2 ounces in 1980, and for that matter I can recall tunafish cans gradually declining from 8 ounces to 6 ounces.) And I remember going to the candy machine with my quarter and picking out the candy bar that was heaviest–I don’t remember which one–even if it wasn’t my favorite flavor, to get the most value for the money.

    But now I realize that, rationally, candymakers should charge more for smaller candy bars. The joy from eating the candy is basically discrete–I’ll get essentially no more joy from a 1.7-ounce bar than from a 1.4-ounce bar. But the larger bar will be worse for my health (no big deal if I eat just one, but with some cumulative effect if I eat one every day, similarly with the sodas and so forth). And, given the well-known fact that nobody can eat just part of a candy bar, I get more net utility from the small bar, thus they should charge more.

  • Michael Schwaeber

    What about the rather favorable marginal cost of the expanded/supersized unit? For example, buy a small 20oz soda at a movie theater for $2.50 or a medium 36oz size for only a quarter more.

  • Nathan Iver O’Sullivan

    Michael, I think Andrew’s point is that the 36oz is actually a worse deal because of our unit bias.

  • Floccina

    I worked in restaurant that sold Pizza and I always thought it silly that many people would ask how many pieces the pizza had (we only had one side Pizza was just a side line). Some people would ask the size and I would give them the diameter some would be happy with that but others would ask how many pieces is that. I wanted to say that we will cut it into as many pieces as you want but I did not.

  • Nathan Iver O’Sullivan

    Based on the discussion so far, the unit bias appears to be almost exclusively a food bias. Why?

  • http://www.aleph.se/ Anders Sandberg

    Mostly an artifact of the initial study (i.e. availability bias). I’m pretty certain unit bias is much more general. I think an easy way to test it would be to look at how people consume other resources like post-its and check whether consumption tends to match package size. The really interesting thing would be to look for conceptual unit bias, where it might round our thinking towards the nearest integer number of convenient units.

  • _Gi

    “We can certainly learn more elaborate programs like “take unit; consume until full; leave the rest”, ”

    This maybe much harder than you think. There is a several minutes lag between satiation and your awareness of it.

  • Tiiba

    My problem is that I buy a snack, see that it’s only a hundred calories, and decide to eat five… And now I have a Twinkie in my gut. What is that called? Perhaps “per-unit” bias?

    This can also be generalized to procrastination and financial wastefulness. A dollar here, a minute there, soon the project is late and over budget.

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