It's the paper behind this TED talk:

http://embed.ted.com/talks/amy_cuddy_your_body_language_shapes_who_you_are.html

I was intrigued by the bold statement, and as I'm pretty skeptical about TED talk, I began reading the paper.

I stopped at this part:

They were endowed with $2 and told they could keep the money—the safe bet—or roll a die and risk losing the $2 for a payoff of $4 (a risky but rational bet; odds of winning were 50/50).

Scientists should learn what economics has known for year. 2$ payoff is not equal to 50% to get 4$ and 50% to get 0.

The average return is the SAME. But the VARIANCE is not! It's totally dumb to choose the 50/50 for the same average return. You should be rewarded for the risk taken, and if your are not, you're making a poor decision. It's common sense -people naturally choose the sure payoff- but it's also backed by economical model, and all the option trading system is based upon how to reward people taking risk.

So as "stretching-guys" tend to choose the risk option, we can conclude that stretching make you dumb.

I hope someone more dedicated than me, can more thoroughly debunk this lecture.