My daughter nursing.

My daughter nursing.

Years and years ago people thought that the biggest predictor of later success would be a child’s IQ.  Of course, they thought, intelligence had to be the be-all and end-all of success; smart people do better and it was that simple.  Only it wasn’t.  It turns out that another variable has become one of the greatest predictors of success later in life: Delay of Gratification (for a review see [1]).

Delay of gratification (DoG) refers to a person’s ability to exercise self-control in the present moment for a greater reward later on.  If one thinks about it, this of course should be a great predictor of success as most of what we do is contingent exercising self-control for later rewards (e.g., work now for pay later, don’t indulge too much in things that are bad for you despite the immediate reward, etc.), but what about young children?  Children were thought to be ruled by impulse so how could we possibly expect any DoG?

It turns out, however, that there is wide variability in DoG in children as young as the preschool age.  The way researchers have classically tested this by bringing kids into a room and telling them they have small or large rewards (predetermined based on the child’s level of interest).  The experimenter explains that she (it’s nearly always a “she”) has to leave the room and gives the child a bell.  If the child waits until the experimenter returns on her own, the child can have the large reward, but the child can ring the bell to bring the experimenter back whenever s/he likes, but if s/he does that, the child has to settle for the small reward (e.g., [2]).

Years of research in this field has found that individual differences in DoG in preschoolers has been linked to various outcomes in adolescence – including academic competence[2][3], drug and alcohol use[4], ability to handle stress[2][3], and social competence[3] – as well as in adulthood – including body mass index[5] and sensitivity to emotional environmental cues/resisting temptation[6].  Even when assessed in older school-age children, it is associated with conscientiousness, intelligence, academic competence, health and social outcomes[7].  In short: It’s a darn good thing to have.

The question us parents are probably asking is: What predicts it?  Clearly there are neurological aspects[6] that likely influence the development of the skill at a later time.  Research has also shown that experience plays a large role in that adolescents who do engage in risky behaviours are likely to rapidly develop delay of gratification abilities such that low-DoG adolescents show vastly improved DoG in later adulthood[4].  However, most of us hope our children don’t have to experience the high risks to get the reward of DoG.

Well, thanks to research out of Switzerland, we can now add one more predictor: Breastfeeding.

That’s right, a relatively recent study examined various maternal and intergenerational factors and how they may influence child DoG[8].  Included in the assessment were child variables such as age, sex, a diagnosis of ADHD, attending kindergarten or not, and siblings.  Maternal variables included household income, breastfeeding duration in months, education, fluid intelligence, crystallized intelligence, the Big Five personality traits, and life satisfaction.  Furthermore, intergenerational relationships between maternal and child DoG, impulsivity, patience, and risk-taking were included.

Of all of these variables, only two were significant predictors of DoG in both a correlational and a binary logistic regression analyses: Child age and breastfeeding duration (with those breastfeeding longer being more likely to show DoG).  These held above and beyond the inclusion of the other variables and the inclusion of child intelligence.  Furthermore, an attempt to find mediating variables (from the one’s assessed) to explain the breastfeeding link failed to yield any significant mediators or moderators (no further mediations on age were looked at because it quite simply makes the most sense of any variable to predict DoG).  The full effect for breastfeeding is that every month of breastfeeding increased the odds of displaying DoG by 11%.  So a child who is breastfed for a year would be 66% more likely to show DoG than a child breastfed for only six months, a child breastfed for 18 months would be 198% more likely to show DoG than a child never breastfed.

So how do we explain the results?  First let’s remember that these results are odds-ratios or relative risk factors.  This means they are not conclusive and there will be children who breastfeed for three years who don’t show DoG and those who didn’t breastfeed at all who do.  I feel that has to be a reminder because people something take these types of results as being guarantees of what will happen instead of just talking about relative risk.  That said, what might be the mechanism behind the relationship?

The authors of the study offer up four hypotheses, all quite interesting and plausible.  First, breastfeeding is really just a proxy for a mother’s investment of time, energy, and interest in the child.  Now this will likely get some people’s back’s raised, but it shouldn’t because again, we know that there are wonderful mothers who never breastfed and shitty mothers who did.  Proxies are not perfect, but by and large there may be enough of a relationship between the two to create the third variable problem in which it’s not breastfeeding per se but the relationship to investment that has resulted in the findings.

Second, the mechanism is via attachment and security.  There was evidence in this cohort that breastfeeding mothers showed greater sensitivity to their children in infancy and as we know from other research, this sensitivity relates to attachment status (e.g., [9]).  In line with this, there is other research that has found that early attachment and responsive mother-child interactions contributes to a child’s development of self-regulation[10].

Third, these results reflect self-regulation differences between breastfed and formula-fed (or bottle-fed) infants, findings that would replicate similar findings on self-regulation of energy intake[11].  It’s unclear if this is a formula v breast or bottle v breast or simply a cue feeding v scheduled feeding issue; however, the issue of self-regulation of energy intake influencing later DoG is something quite plausible and worthy of discussion.  Of course, further discussion of why (i.e., is it the food itself, the way it’s given, or the type of feeding) is something that would deserve quite a bit of research as well.

Finally, the results may reflect neurological differences that are influenced by the fatty acids found in breastmilk that are not present to the same degree in formula.  In this scenario, the duration of breastfeeding would influence the amount of fatty acids that would have made their way to the developing brain which would influence frontal lobe development which is where DoG processes have been found[12].

Of course, it is also possible that all of these are influencing the findings in different degrees or that none of them explain the reasons for the effect.  For moms who didn’t breastfeed or who didn’t breastfeed for a long time, is there cause to worry?  No.  No one is saying you’re going to have a child with no sense of self-regulation because of that one act.  Remember this is simply information and relative risk information at that and that there are many other variables that will influence DoG.  Although some mothers find themselves feeling guilty or judged upon reading this, I want to remind everyone that this research doesn’t speak to anyone’s specific situation and indeed this type of information can only serve to better things for everyone.  If we learn the mechanism behind this finding (as well as replicate it) then we can find ways to change things.  In the interim, it’s just one more piece of information for parents to weigh when making decisions about how they plan to feed their baby.

[1] Mischel W, Shoda Y, Rodriguez ML.  Delay of gratification in children.  Science 1989; 244: 933-8.

[2] Shoda Y, Mischel W, Peake PK.  Predicting adolescent cognitive and self-regulatory competencies from preschool delay of gratification: identifying diagnostic conditions.  Developmental Psychology 1990; 26: 978-86.

[3] Mischel W, Shoda Y, Peake PK.  The nature of adolescent competencies predicted by preschool delay of gratification.  Journal of Personality and Social Psychology 1988; 54: 687-96.

[4] Romer D, Duckworth AL, Sznitman S, Park S.  Can adolescents learn self-control? Delay of gratification in the development of control over risk taking.  Prevention Science 2010; 11: 319-30.

[5] Schlam TR, Wilson NL, Shoda Y, Mischel W, Ayduk O.  Preschoolers’ delay of gratification predicts their body mass 30 years later.  Journal of Pediatrics 2013; 162: 90-3.

[6] Casey BJ, Somerville LH, Gotlib IH, Ayduk O, Franklin NT, et al.  Behavioral and neural correlates of delay of gratification 40 years later.  PNAS 2011; 108: 14998-15003.

[7] Duckworth AL, Tsukayama E, Kirby TA.  Is it really self-control?  Examining the predictive power of the delay of gratification task.  Personality and Social Psychology Bulletin 2013; 39: 843-55.

[8] Drobetz R, Maercker A, Spiess KC, Wagner GG, Forstmeier S.  A household study of self-regulation in children: Intergenerational links and maternal antecedents.  Swiss Journal of Psychology 2012; 71: 215-26.

[9] Britton JR, Britton HL, Gronwaldt V.  Breastfeeding, sensitivity, and attachment.  Pediatrics 2006; 118: 1436-43.

[10] Winsler A, Diaz RM, McCarthy EM, Atencio DJ, Chabay LA.  Mother-child interaction, private speech, and task performance in preschool children with behavior problems.  Journal of Child Psychology and Psychiatry, and Allied Disciplines 1999; 40: 891-904.

[11] Dewey KG, Lonnerdal B. Infant self-regulation of breast milk intake.  Acta Paediatrica 1986; 75: 893-8.

[12] Zelazo PD, Muller U.  Executive function in typical and atypical development.  In U Goswami (Ed) Handbook of childhood cognitive development (pp. 445-69).  Oxford, UK: Blackwell, 2002.