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Does eating chicken on the bone make children more violent?

That is the finding of a study published in the journal Eating Behaviors.  I have a lot of admiration for the study's lead author, Brian Winsink (I highly recommend his book Mindless Eating), but I'm going to have to file this one under "I don't believe it."  

I thought it was worth weighing in on since I'd seen the study reported on in several major media outlets.  I'm not saying that it isn't possible that eating chicken on the bone (vs. in chunks) doesn't cause aggression, I'm just saying that my priors are such that it will take a lot more than this to convince me.  

Why would we even expect that eating chicken on the bone causes aggression?  The authors suggest the following hypothesis:

Showing teeth is a common sign of aggression in the animal world. Dogs retract their lips and bare their teeth as a sign that they are willing to fight (Galac, & Knol, 1997). The baring of teeth may have similar meaning in intuitive human behavior

So, the authors ran an experiment.  

They took 12 children participating in a 4-H summer camp (yes, N=12), and split them in two groups, 6 in one and 6 in another.  On day 1, one group was fed chunks and the other group was fed chicken on the bone.  On day 2 , they reversed the foods fed to the groups.  On both days, the children's behavior was monitored and recorded.  For example, the children were asked to stay in a circle and the monitors counted the number of times the children left the circle (glad I didn't go to that 4-H camp!).  Paired t-tests were used to test whether behavior differed on the day the child got the bone vs. the chunk.

Here are some shortcomings of the study that make the results a bit hard to believe:

  • The small sample size.
  • Each child was only observed on 2 days (one with bone one with chunk).  However, on one day, the temperature was 97 degrees and on the other it was 76.  Lots of prior research has posited a link between temperature and aggression (hot = more aggressive).  Suppose you had a couple kids in a group with a tendency toward aggression who got assigned chunks on the colder (76 degree) day and bones on the hotter (97 degree) day?   The difference in their behavior may be due to temperature not bones.  It would be nice to see tests for within-day differences in bone vs. chunk.  If one had a large sample with random assignment to treatments on multiple days this wouldn't be as much of a concern, but it certainly is here.
  • Children assigned to the same group sat at the same table together.  This may have produced some sort of group dynamic.  Suppose, for example, the kids assigned to bone started arguing at the table and the conflict spilled over to the playground.  The current study cannot separate group-day effects from the treatment effect (bone vs. chunk).
  • Given the small sample size, really all it takes is one or two kids changing behavior from day 1 to day 2.  How do we know this wasn't due to something at home that carried over to the camp?  With such a small number of observations, I don't know why the authors didn't just report the entire data set in one table.  That way, we could see whether the difference was from a small increase in aggression of every child or a large increase in aggression of 1 o 2 kids.  
  • The counselors who kept the kids in the circle and who rated behavior were "blind" as to the treatment and control groups each day. That's good.  However, the study doesn't tell us whether the people who subsequently watched the videos and rated behavior were also blinded.
  • Maybe the effect exists but for very different reasons than those hypothesized in the paper.  I've already mentioned a temperature explanation.  What if children like to eat chicken on the bones more than they do in chunks (my kids certainly do).  Maybe they get more excited and rambunctious when they get a "treat" or something they like, which the current authors attribute to "aggression."  Perhaps when the counselors give the kids a food that the kids perceive as more generous or benevolent, it signals to the kids that the counselors will subsequently be more permissive.  To control for this, you'd want some treatments where the bone-in food was less desirable than the boneless food.

At the end of their article, the authors suggest a number of lines of additional research that are interesting and worthwhile.  But, they also give some advice.   The authors suggest

school cafeterias may reconsider the types of food they serve if it is known that there are behavioral advantages to serving food in bite-size pieces

and

it may not be wise to serve young children chicken wings shortly before bedtime, or to serve steak and corn-on-the-cobb in the company of dinner guests.

That may be good advice in general, but this study alone is insufficient reason to re-engineer lunch lines or dinner plans in an effort to reduce child aggression.  

  

A new way to stop food waste?

Food waste has been in the news quite a bit recently. As I've previously mentioned, it is unlikely economically optimal to completely eliminate food waste.  That said, one thing that most folks can probably agree on is that we do not want to enact government policies that encourage more food waste.  

Yet, according to a couple recent papers by Cornell economists, the school lunch program is doing just that.  

The first study, in the journal Public Health Nutrition, the authors (Just and Price) used in-school experiments and found that requiring schools to place additional servings of fruits and vegetables on kids' plates in a school lunch line (as is required by new standards), causes a small increase in fruit and vegetable consumption but also a huge increase in waste.   The authors report (from one of their two studies) that:

However, as more items were served the fraction of items being thrown away more than doubled for those students taking just one serving (from 39 % up to 82 %) and also increased for those students taking two or more servings (from 45 % up to 60 %).

Some of the media discussion surrounding the article suggests that:

For every one to two children who eat fruits or vegetables under the new federal guidelines, five throw them away, the researchers said.

Which results in $3.8 million being thrown away each year.  The authors other research suggest that it may make more economic sense to provide financial incentives for kids to eat fruits and veggies rather than simply requiring more be placed on a tray. 

In another study by David Just (this time with co-authors Andrew Hanks and Brian Wansink) appearing in PLoS ONE, looked at the effects of another school lunch policy: banning chocolate milk.  Again, the authors compared treatment and control schools that had different policies (or before and after policy changes) and found the following:

Removing chocolate milk from school cafeterias may reduce calorie and sugar consumption, but it may also lead students to take less milk overall, drink less (waste more) of the white milk they do take, and no longer purchase school lunch. 

Although more students took white milk after the chocolate milk ban, they wasted about 29% more than before the ban.   

David Just and his colleagues at Cornell have been studying all kinds of ways to increase fruit and vegetable consumption among school children by doing things link re-orienting lunch lines, placing kid-friendly stickers on fruits and veggies, providing economic incentives, changing payment methods, etc.  I like this experimental approach to seeing what works - particularly when paired with research on cost-effectiveness.  But, as their research shows, simply banning foods or mandating that schools plate more fruits and veggies is largely ineffective and wasteful.  

Food Demand Survey (FooDS) - The First Year

The Food Demand Survey (FooDS) has now been ongoing for a full year!  

We've pulled together summary statistics on the key variables we've tracked over time.

For example, here is an index of awareness (how much people have heard or read about an issue in the preceding two weeks) and concern over the past year, for the four issues that seem to top the lists each month (in total, we track 17 items). 

Awareness is much more variable over time than is concern.  

The spike in awareness for Salmonella in October, 2013 corresponds with a widely publicized Salmonella outbreak from a California poultry processor (Foster Farms).  

It interesting to compare the Salmonella spike in awareness with external data sources.  I searched the term "Foster farms" (shown in blue below) and "Salmonella" (shown in red below) in Google trends over the past year.  Google trends, according to Wikipedia,  "shows how often a particular search-term is entered relative to the total search-volume."  The volume of searches measured by Google, both the October spike and the smaller rise in January and February, match up quite will with our measure of awareness shown in figure 2 above.  

Of course, the thing we have that Google analytic doesn't, is information on concern for issues on on willingness-to-pay for chicken and other meat products.

Curiously, despite the spike in awareness of Salmonella in October, we did not observe big changes in concern for Salmonella  or huge changes consumer willingness-to-pay or plans to buy chicken.  

Of course, our survey is more than just about this single incident or issue, but the preceding discussion is an example of the kinds of insights we hoped FooDS would deliver.

Read the whole summary here.