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Oct. 25, 2012 Volume 34, No. 10

Infants unable to differentiate object size in some cases, MU study finds


Study could help develop child education programs

Human brains process large and small numbers of objects using two different mechanisms, but infants have not yet developed the ability to make those two processes work together, according to a study from the University of Missouri.

“This research was the first to show the inability of infants in a single age group to discriminate large and small sets in a single task,” said Kristy vanMarle, assistant professor of psychological sciences in the College of Arts and Science. “Understanding how infants develop the ability to represent and compare numbers could be used to improve early education programs.”

In vanMarle’s study, 10- to 12-month-old infants were presented with two opaque cups. Different numbers of breakfast cereal pieces were hidden in each cup while the infants watched. The infants were allowed to choose a cup. Four comparisons were tested between different combinations of large and small sets. 

Infants consistently chose two food items over one and eight items over four, but chose randomly when asked to compare two versus four and two versus eight.

“Being unable to determine that eight is larger than two would put an organism at a serious disadvantage,” vanMarle said. “However, ongoing studies in my lab suggest that the capacity to compare small and large sets seems to develop before age two.”

The ability to make judgments about the relative number of objects in a group has evolutionary roots. 

Dozens of species — including some fish, monkeys and birds — have shown the ability to recognize numerical differences in laboratory studies. 

VanMarle speculated that being unable to compare large and small sets early in infancy might not have been problematic during human evolution because young children probably received most of their food and protection from caregivers.