I'm skeptical of IQ enhancing drugs ever coming about. Intelligence is so complex even the actual definition is a controversial topic. So far we can show that intelligent enhancement can be predicated on exercise, outside of that there are temporary drugs (e.g. coffee) that "boost" intelligence but in actuality boost attention.
"In the first test, conducted in Northern California in the late 1960s, a researcher named Calvin Edlund selected 79 children between the ages of 5 and 7, all from “low-middle class and lower-class homes.” The children were randomly divided into an experimental group and a control group. First, they all took a standard version of the Stanford-Binet IQ test. Seven weeks later, they took a similar test, but this time t…
Forget the M&M's. Video games are a skinner box on steroids. Kids are going to learn fast.
Edit: I may have missed the point -- it looks like motivation improves performance, not necessarily actual "cognitive ability", if we can quantify that.