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Old 03-13-2016, 03:15 PM
KarlGauss KarlGauss is offline
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Another factor that may influence handedness is breastfeeding, with breastfed infants being less likely to be left-handed (alas, the full text of the article is not free).

The brief excerpt below from the above-cited paper discusses possible mechanisms to account for the relationship between breastfeeding and handedness:
Originally Posted by Denny
Possible connections between breastfeeding and laterality have been noted by other researchers. Numerous studies have investigated lateralisation in the tendency of individuals to hold infants and objects representing infants (such as dolls), finding that in general the left hand is used preferentially. This seems to be particularly true for women (for example, Van der Meer & Husby, 2006). Harris, Cárdenas, Michael, Spradlin, and Almerigi (2009) summarise much of the evidence and the possible explanations. One is that this left bias makes it easier for an infant to hear (and be soothed by) the mother's heartbeat. A second theory, the attention-emotional arousal hypothesis, is that babies cradled on the left are better able to perceive emotional signals or cues from the mother since parts of the right hemisphere are dominant in the perception of emotion and for wakefulness and arousal. While these results do not directly relate to breastfeeding, it seems very plausible that this bias may influence how mothers breastfeed.

In a separate set of findings Engstrom, Meier, Jegier, Motykowski, and Zuleger (2007) present evidence that the right breast produces about 20% more milk than the left, and discuss a number of other studies that have also found this bias. Since the mothers in that study were pump dependent throughout lactation this eliminates the influence of maternal or infant behaviour as an explanation. How this might relate to an effect of breastfeeding on handedness is far from clear.