We expected that if these two abilities were connected, only children who improved in text comprehension would improve in idiom comprehension as well.
A positive value of d indicates the presence of higher ability among the only children, and a negative value the reverse.
The number of only children in the samples ranged from eight to 78,053.
First, when compared to other birth orders, only children were consistently different from middle-born, and less consistently different from last-born children.
Only children also compared favourably with all those with sibs.
Importantly, only children with at least average-for-age reading accuracy were included in our studies.
Nor is it only children who are misdiagnosed in this way.
However, only children who met the above explicit criteria were retained.
