Some people, including journalists and scientists, think that the Flynn effect-- the finding that IQ rose steadily during the 20th century--proves that genes play little to no role in explaining differences in IQ. But how can this be? Twin studies show that genetic differences explain an awful lot of the variation in IQ. The key to this puzzle is understanding what will happen when breakdancers take over the world.

What psychology experiment would you love to carry out if neither ethics nor practical reality stood in your way? For the August issue of Psychology Today, I asked several PT bloggers this question and printed four responses. Here's a more complete roundup of their insights.

Cases of mistaken identity often reveal an unknown twin.

Fraternal twins are there--but you may not see them.

Quads come in all shapes and sizes

Unusual sibships emerge in families with twins!

How do we explain great athletic skill?

Many twins get their twin type wrong

Identical twins are intriguing, but most people cannot tell you why this is so. I think I have an answer . . .