I've done the googling that Annoyance considers so vital to our moral development. Here are the results, for those who wish to remain slothful and debased. For the truly pious, youtube has a video of the so-called icepick psychosurgery from a PBS documentary.

1. Googling "effect of lobotomy on IQ" returns a Google Books excerpt from a Neuroscience textbook. The author is professor of Neuroscience at MIT. The text claims that "...lobotomy can be performed with little decrease in IQ..." It also says that in the most popular lobotomy technique, it was impossible for the doctor to see what sections of the frontal lobe he was "treating."

2. An online psychology textbook here describes the behavior of lobotomy patients as "stimulus-bound," and reports that they were easily distracted by their immediate surroundings and had little ability to plan or set goals.

3. This site and this book (see p. 20) have more information on the general effects of damage to the frontal lobe.