A new study published in Current Biology finds that mothers underestimate the height of their youngest child; no matter how many children they have (Kaufman et al., 2013).
The study found that mothers underestimated their youngest child’s height by an average of 3 inches (7.5cm). This finding held even for only children.
This is set against the fact that mothers were pretty accurate when asked to indicate the height of their other children, and of everyday objects.
The lead author Jordy Kaufman, explained:
“Contrary to what many may think, this isn’t happening just because the older child just looks so big compared to a baby. It actually happens because all along the parents 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.”
To reach this conclusion, 70 mothers were asked to place a mark on the wall estimating the height of each child. Across the mothers, the youngest child’s height was consistently underestimated.
The authors argue that this is an evolutionary adaptive mechanism that encourages mothers to nurture the youngest child.
The researcher’s interest was piqued when they surveyed 747 mothers, asking if they had noticed a spurt in the height of their ‘erstwhile-youngest’ child, when their next was born.
More than 70% of mothers said they had noticed this growth spurt and many agreed that it seemed to happen overnight.
Whether or not an evolutionary explanation is valid, this study certainly shows the effect of our knowledge and feelings on our perceptions. Kaufman continued:
[Note: children whose height was estimated were between 2 and 6 years of age–the findings may not hold for older age-groups.]
“The key implication is that we may treat our youngest children as if they are actually younger than they really are. 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.'”
About the author
Psychologist, Jeremy Dean, PhD is the founder and author of PsyBlog. He holds a doctorate in psychology from University College London and two other advanced degrees in psychology.
He has been writing about scientific research on PsyBlog since 2004. He is also the author of the book “Making Habits, Breaking Habits” (Da Capo, 2003) and several ebooks:
- Accept Yourself: How to feel a profound sense of warmth and self-compassion
- The Anxiety Plan: 42 Strategies For Worry, Phobias, OCD and Panic
- Spark: 17 Steps That Will Boost Your Motivation For Anything
- Activate: How To Find Joy Again By Changing What You Do
Image credit: Sergiu Bacioiu