A brief lesson in viscosity

I welcomed the article “What Black Holes Teach About Strongly Coupled Particles,” by Clifford Johnson and Peter Steinberg (Physics Today, May 2010, page 29), as I hoped to learn something about black holes and particle interactions.

But I was shocked when reading about viscosity in the first paragraph. I presumed that viscosity relates to forces between adjacent particles and that weak interactions would thus correspond to low viscosities. Imagine my surprise at reading that “low shear viscosities indicate significant interaction strength.” I would appreciate being corrected if I hold a misconception about the relation between interaction strength and viscosity.