No single thing is a "true sign of intelligence", that is to ignore the mutual interdependence of things. You can't have imagination without any knowledge.
http://en.wikipedia.org/wiki/Jeff_Hawkins#Neuroscience
to make sure you were referring to the author whose book I have perused before. I will note for the record that Hawkins has not won wide acceptance for his view of intelligence among other researchers to date.
http://lesswrong.com/lw/va/measuring_optimization_power/
Eliezer Yudkowsky described this pretty well.