Longer Breastfeeding Predicted Better Self-Control at Age 3.5 in Quebec Longitudinal Cohort

TL;DR: A 2026 longitudinal study in Appetite following 491 Quebec children found that infants breastfed for at least three to six months showed better inhibitory control — the ability to suppress an automatic response — at age three and a half than infants who were never breastfed, with the largest behavioral benefits in those breastfed for more than six months.

Source: Appetite (2026) | Jacques et al.

Inhibitory control is the executive-function component that lets a child suppress an automatic or impulsive response and choose a more appropriate one.

It develops most rapidly between ages three and five, and stronger inhibitory control in childhood predicts better health and financial outcomes in adulthood.

This study tested whether one specific early-life experience — direct-from-the-breast feeding — provided repeated practice that might strengthen this skill.

Why Direct Breastfeeding May Train Stop-on-Internal-Cues Behavior

The authors’ hypothesis builds on existing appetite-regulation work showing that breastfed infants have lower obesity risk, possibly because nursing trains the infant to stop eating based on internal fullness cues rather than external ones.

The mechanism turns on a structural difference between feeding methods:

• Bottle feeding: Parents can see exactly how much milk remains and may, intentionally or not, encourage the infant to finish — pulling the regulation cue from internal fullness to “the bottle is empty.”
• Direct breastfeeding: Parents cannot see the volume consumed, so the infant’s stopping decision is anchored on internal fullness signals.

The team extended this mechanism beyond appetite. If breastfed infants get repeated practice at acting on internal cues to stop a strongly motivated behavior, that practice may transfer to inhibitory control more generally.

491 Children From the Quebec Longitudinal Cohort Tested at Age 3.5

The analysis used data from the Québec Longitudinal Study of Child Development.

• Initial sample: 572 infants enrolled.
• Final sample: 491 children completed the cognitive testing at age 3.5.
• Breastfeeding measurement: Mothers reported breastfeeding status and duration at infant ages 5 months and 17 months.
• Duration groups: never breastfed; less than 3 months; 3 to 6 months; 6+ months.
• Pre-pump era: Children were born before breast pumps were widely available in Quebec, so reported breastfeeding mostly reflected direct-at-the-breast feeding rather than expressed-milk bottle feeding.

At age 3.5, researchers visited each child’s home for direct cognitive testing and collected mother-reported behavioral data.

Two Direct Tests of Inhibitory Control Were Used

Researchers used two structured tasks designed to measure inhibitory control directly:

• Luria’s Hand Game: An adult shows the child a hand gesture (closed fist, flat hand) and the child must do the opposite. The child has to suppress the automatic urge to copy.
• Sun-Moon Stroop-style task: Children see a sun and must say “night”; they see a moon and must say “day.” This requires overriding the automatic visual-to-verbal mapping.

Mothers also completed questionnaires rating each child’s hyperactivity and inattention over the previous six months.

That mix of direct task performance plus parent-reported behavior allowed the team to test whether breastfeeding duration was associated with both controlled-task performance and real-world self-regulation.

Breastfeeding Duration Predicted Better Inhibitory Control at 3.5 Years

Children breastfed for at least three to six months performed better on Luria’s Hand Game than children who were never breastfed.

The pattern continued in the everyday-behavior data:

• Less fidgeting: Mothers of breastfed children less often described their child as fidgety.
• Less impulsivity: Reported impulsive behavior was lower with longer breastfeeding duration.
• Better concentration: Reported concentration was stronger.

The effect was strongest for the more-than-six-months group, consistent with a dose-response pattern where more practice corresponded to stronger inhibitory-control outcomes.

The Effect Was Specific to Inhibitory Control

One of the more useful findings is what breastfeeding duration did not predict.

The team measured three executive-function domains:

• Inhibitory control: Suppressing an automatic response (the focus of the study).
• Working memory: Holding and updating information in mind to solve a problem.
• Cognitive flexibility: Shifting perspective or switching task rules.

Breastfeeding duration predicted inhibitory control. It did not predict working memory or cognitive flexibility.

That specificity supports the self-restraint-training hypothesis. If breastmilk simply boosted general brain development, all three executive-function domains should have shifted together.

The fact that only the inhibitory-control measure moved is consistent with the authors’ “on-the-job training” framing rather than a generic neurodevelopmental effect.

Reverse Causality and Nutritional Mechanism Could Not Be Separated

• No causal claim: The design is correlational. The authors explicitly state that the data cannot show that breastfeeding caused the inhibitory-control improvements.
• Reverse direction is plausible: Mothers may stop breastfeeding earlier when their infants show early self-regulation difficulties — making the cause-effect arrow run from infant temperament to feeding duration rather than the other way.
• Nutritional vs behavioral mechanism is not separated: Breastmilk contains specific trace nutrients that may support neurological development. Disentangling chemical contribution from behavioral practice would require designs this study did not run.
• Pre-pump cohort limits generalization: The “breastfeeding usually means at-the-breast” assumption is true for this older Quebec cohort but does not transfer cleanly to current populations where expressed-milk bottle feeding is common.
• Mother-reported behavior is subjective: Half the inhibitory-control evidence comes from maternal questionnaires, which can be biased by maternal beliefs about feeding choice.

Bottle Feeding Does Not Block Self-Regulation Training If Parents Read Infant Cues

The authors are notably cautious about how the results are framed:

• Breastfeeding is not always feasible: The team explicitly states that medical, practical, and personal reasons may make breastfeeding impossible or undesirable for many families, and they do not want the findings used to assign blame.
• Bottle feeding does not block self-regulation training: Parents who feed from a bottle can still pay close attention to infant fullness signals rather than focusing on emptying the bottle.
• Other infant routines may serve the same purpose: Self-soothing, sleep routines, toilet training, and other developmental challenges all give children practice acting on internal cues. Breastfeeding is one route, not the only one.
• Practice is the underlying claim: The broader takeaway is that opportunities to exercise self-control during infancy and early childhood — across many domains — may matter more than any single feeding choice.

For researchers, the cleanest next step would be a study that holds breastmilk-nutrient exposure constant while varying the behavioral feeding style — direct-at-breast versus expressed-milk bottle — to separate the chemical from the behavioral component the authors hypothesize.