Mothers see their youngest as shorter than they are

December 16, 2013
Image: Wikimedia Commons

Many parents say when their second child is born that their first child suddenly appears to have grown overnight. Now, researchers reporting in the Cell Press journal Current Biology on December 16 have an explanation: until the birth of the new child, those parents were subject to a "baby illusion," routinely misperceiving their youngest child as smaller (and younger) than he or she really was.

"Contrary to what many may think, this isn't happening just because the older just looks so big compared to a baby," says Jordy Kaufman of Swinburne University of Technology in Australia. "It actually happens because all along the were under an illusion that their first child was smaller than he or she really was. When the new baby is born, the spell is broken and parents now see their older child as he or she really is."

Kaufman and his colleagues made the discovery first by asking 747 mothers if they remembered experiencing a sudden shift in their first child's size after the of a new infant. The researchers found that 70% of the mothers did.

To further explore that perceptual shift, the researchers asked mothers to estimate the of one of their young children (aged 2 to 6) by marking a blank wall. When the researchers compared those height estimations to the child's real height, they found something very interesting: mothers significantly underestimated the height of their youngest child by 7.5 cm on average. In contrast, height estimates for the eldest child were almost accurate.

"The key implication is that we may treat our youngest children as if they are actually younger than they really are," Kaufman says. "In other words, our research potentially explains why the 'baby of the family' never outgrows that label. To the parents, the baby of the family may always be 'the baby.'"

The findings are a useful reminder of just how filtered our own perceptions of the world around us can be.

"We cannot trust the accuracy of our perceptions," Kaufman says. "In this case, it shows that our feelings and knowledge of our children affect how we actually perceive them. But it's important to consider that this misperception may actually make it easier to quickly distinguish one's youngest child from the other ."

Explore further: Birth of a first baby can trigger anxiety

More information: Current Biology, Kaufman et al.: "Parental misperception of youngest child size"

Related Stories

China: Birth limits still needed despite easing

November 19, 2013

China has no intention of abandoning family planning controls soon despite announcing it would ease the one-child policy, a government spokesman said Tuesday, adding that the policy could be loosened further in the future.

Recommended for you

Serious research into what makes us laugh

November 24, 2015

More complex jokes tend to be funnier but only up to a point, Oxford researchers have found. Jokes that are too complicated tend to lose the audience.

Psychologists dispute continuum theory of sexual orientation

November 19, 2015

Washington State University researchers have established a categorical distinction between people who are heterosexual and those who are not. By analyzing the reported sexual behavior, identity and attraction of more than ...

Babies have logical reasoning before age one, study finds

November 18, 2015

Human infants are capable of deductive problem solving as early as 10 months of age, a new study by psychologists at Emory University and Bucknell finds. The journal Developmental Science is publishing the research, showing ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.