Breastfeeding and mommy wars

Last week, a paper came out in a relatively obscure journal and got a lot of attention (or at least got its own #slatepitches headline). A sociologist at Ohio State published a study saying that the positive effects of breastfeeding essentially disappear if you look at within-sibling differences. That is to say if you compare two siblings from the same parents, one of whom was breastfed and one of whom wasn’t, there isn’t much in the way of statistically significant differences in their educational achievement, health status, or intelligence as measured by standardized tests.

In many ways, this isn’t surprising. We already know that the vast majority of our later life outcomes are determined by our parents’ incomes and education levels, where we grow up, how many words are said to us before we can even talk, and the myriad investments our parents make in our parents’ health. That breastfeeding doesn’t make a very big difference among siblings shouldn’t surprise us.

Perhaps even more important though, and this is really the kicker when trying to identify the effects of early childhood interventions, is that we don’t know what else the parents did differently for these two children. Given what we know about mothers who breastfeed—they tend to be wealthier and more educated, they get more assistance with breastfeeding education, they tend to have more flexible jobs that allow them to breastfeed for longer, or are staying at home with their kids, they’ve been told for years, etc.—we also expect them to be conscientious if they for some reason are not breastfeeding one of their children. Colen’s analysis can only control for time-invariant, mother-specific characteristics. An important omission is that she can’t control for mothers who supplement bottle-feeding with additional doctor’s visits, vitamins, extra care, more time spent together, or any other activity or characteristic that would act as a complement to breastfeeding. It ignores anything that might cancel out the fact the child isn’t getting the extra nutrients and other stuff that we ascribe to breastfeeding.

This omission is only important if it’s correlated with breastfeeding, and in all likelihood, it is. If you thought your child was missing out by not being breastfed, mothers with the ability to might try to compensate by increasing other investments.

It’s also worth noting that there are other studies using the same methodology that do find within-family effects for breastfeeding. This one, for instance, by Rees and Sabia.

Ultimately Colen wants to use the results to push for more family-friendly social policy, like increased maternity leave and more. But this is not the last word on breastfeeding. One momy blogger called it a “suspect methodology.” It’s not, it’s a perfectly valid methodology, but we need to be careful about what it’s actually showing.


Rees, Danial and Joseph Sabia. 2009. “The Effect of Breastfeeding on Educational Attainment: Evidence from Sibling Data.” University of Colorado at Denver Working Paper 09-03.

Colen, Cynthia and DM Ramey. 2014. “Is Breast Truly Best?:Estimating the effects of breastfeeding on long-term child health in the United States using sibling comparisons.”Social Science and Medicine.

Hart, B. & Risley, T.R. “The Early Catastrophe” (2004). Education Review, 77 (1), 100-118.

Awesome things at SVRI Forum

After an awesome week in Bangkok, I thought I’d share some of the conversations, research, and events that happened last week because I’m feeling privileged to have been able to spend time with such a diverse, animated group of researchers and people passionate about ending sexualized violence. It was a singular experience, to be sure, and I can’t wait for the next one. Below is a partial list of the awesome things I saw and heard at the SVRI Forum in Bangkok, in no particular order.

  • Research on LRA child soldiers and the harsh methods used to control them by Jocelyn Kelly of the Harvard Humanitarian Institute.
  • Tweet-ups. Such a fantastic group tweeting the Forum and interacting online. Storified here.
  • An Egyptian woman recounting how she and her daughter went to the Tahrir protests for two weeks in a large group of women, and how her daughter became more autonomous, independent, and opinionated as a result.
  • A Bhutanese woman talking lovingly of her King, who she thinks looks like Elvis Presley, and the modest cottage he inhabits.
  • Limited positive effects of cash transfers on instance of intimate partner violence in Ecuador by Amber Peterman of the school that shall not be named.
  • An American woman recalling the 70s in Berkeley and abortion activists offering to pay her to get arrested to perform an abortion without a license
  • The same American woman recalling her interactions with rural Japanese housewives.
  • Lots of UN and NGO politics.
  • A Kenyan woman surmising that Kenyatta has the potential to be Kenya’s greatest president yet, if (and that’s a big IF) he doesn’t end up being a war criminal.
  • Thai food. So much wonderful, delicious Thai food.
  • Kate Falb of the Yale School of Public Health on multi-faceted interventions addressing gender inequality and economic empowerment in Cote d’Ivoire.

There were so many more. Check out all the presentations online.

Children’s health and recall

One of the primary problems with survey research is that it relies on recall of past events. In as much as humans are subject to forgetting things (and we are actually designed to forget things), asking someone about how often they perform an activity or how often something has happened in the past few weeks or how much they paid for something is problematic. This is before we even factor in the cultural norms and expectations around the behavior. We probably exaggerate the things we’re proud of of or that match social norms and downplay the incidence of events we’re ashamed of. Econometrically, we tend to say this kind of error is only a problem if it is systematic. That is, if some people overestimate and some people underestimate (with mean zero and some constant standard deviation), it won’t affect our estimates. However, if everyone underestimates, this causes our parameter estimates to be biased. In simpler terms, we don’t accurately assess the relationship between two variables because we’re missing a lot of information about at least one.

A paper explains this problem as it relates to diarrhea incidence recall by parents and definitions (which also gets me thinking about language, and education, but that’s another post or two or three).

Several methodological issues may have an impact on the incidence rates of childhood acute diarrhea reported by community-based studies. This study was performed to assess the impact of parental recall ability and definition of diarrhea on the estimate of incidence of acute diarrhea. Eighty-four children younger than 40 months were randomly selected and visited every other day for four weeks and the occurrence of diarrhea was registered. On the last day of the study, another visit was performed and the informants were inquired about the occurrence of diarrhea during the previous four weeks. Data gathered during the four weeks were compared to those obtained on the last visit. Additionally, the informants’ definition of diarrhea was investigated and compared to the one adopted by this study. During the observation period, 33 children suffered diarrhea, but only 10 (30.3%) informants reported the occurrence of diarrhea. Although 42.4% of those informants reported that their children had been ill over that period, they did not report diarrhea. Further, 60.6% children who had diarrhea suffered at least one episode in the two weeks prior to the visitation. The same definition of diarrhea used in this study was adopted by 52.1% of the informants inquired. Parental recall is an unreliable method to estimate the incidence of diarrhea and studies with a short interval between the visits should be necessary to correctly evaluate this important health problem. Moreover, assessing the informants’ own definition of diarrhea is a significant contribution to the interpretation of the results.

The rub is that we’re not very good at recalling past events, even when we’re being constantly reminded of them. As a separate, but related question, I wonder whether our ability to recall changes over time, or more specifically, over the course of an intervention. I wonder if the percentage of recall changes when you’ve been a recipient of an education program or a new latrine or whether that percentage stays constant. Depending on what the answer is, it could have a large impact on how we evaluate the effectiveness of health and sanitation interventions.