Study Reveals ‘Baby Illusion’ Where Parents See Youngest Child Smaller than Older Children

Bringing a newborn baby home is surreal. Everything looks so alarmingly large – the crib, the car seat, even the clothes that they’ll wear in just a matter of weeks or months. But there’s probably nothing that looks bigger in comparison to a newborn than their older sibling.

tiny newborn

According to Jordy Kaufman, a senior research fellow at the Brain & Psychological Sciences Research Center at Swinburne University of Technology in Australia, many moms having a subsequent children report the very same thing. He and his colleagues initially surveyed 747 mothers. More than 70 percent of them reported that their previously youngest child suddenly seemed larger when compared to the family’s newest addition.

“A lot of parents had expressed the feeling that they almost lost a baby when they got another one,” Kaufman told Today.

To see if this was an honest misconception held within the brain, or simply that ‘everything looks big compared to a newborn,’ Kaufman then asked 77 of the moms to estimate the height of one of their children between the ages of 2 and 6. That estimation was then compared to the actual height.

On average, when the mother estimated their youngest child’s height, they were off by almost three inches. This was true, even if the child did not have any older siblings. However, when asked to estimate the height of their oldest child, moms tended to guess accurately.

Published Monday in the journal of Current Biology, Kaufman called the study-confirmed phenomenon the ‘baby illusion.’ This illusion causes parents to perceive their youngest child as smaller than they really are. The result is surprise at how much bigger the older child appears to be.

Interestingly enough, Kaufman believes there is actually a purpose behind this misconception. He says that it’s possible that the ‘baby illusion’ leads to better caregiving. He says that the perception of smaller size and baby-like features could actually help parents prioritize care for the child that most needs it. This may even explain why the ‘baby of the family’ is always seen as the baby, even long after they’ve grown up.

What do you think? Did your older children seem larger when you brought your baby home? We’d like to hear about your experience.

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About the author


Kate Givans is a wife and a mother of five—four sons (one with autism) and a daughter. She’s an advocate for breastfeeding, women’s rights, against domestic violence, and equality for all. When not writing—be it creating her next romance novel or here on Growing Your Baby—Kate can be found discussing humanitarian issues, animal rights, eco-awareness, food, parenting, and her favorite books and shows on Twitter or Facebook. Laundry is the bane of her existence, but armed with a cup of coffee, she sometimes she gets it done.

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