(FORTUNE Magazine) – We dedicate this item to a highly agitated chap observed on a recent Donahue show about IQ, a subject we have trouble staying away from even while browsing on the tube. As almost invariably happens in any public forum where the subject gets addressed, the ''hereditarians'' were on the defensive. Hereditarians, represented in this case by J. Philippe Rushton of the University of Western Ontario, are folks who state that IQ differences between individuals mainly reflect differences in their genes. Relentlessly egged on by Phil Donahue, the audience turned into a howling mob committed to an egalitarian and more lovable view: that differences in mental ability have only environmental origins. Or as the agitated party put it all too succinctly, ''Everything is environmental. You know, this crap ((Rushton's)) talking up here is just a bunch of garbage.'' By an eerie coincidence, we caught the Donahue show on the very day we received the latest quarterly issue of Intelligence. For readers of this scholarly publication, the issue of IQ heritability has long been settled: There is an overwhelming case that genetic factors account for the bulk of IQ differences. Unfortunately, a good part of this case remains inaccessible to laypersons of the type who show up in Phil Donahue's studio, as it has been developed via regression equations that are tough to grasp if you never got beyond elementary algebra. Far more graspable at an intuitive level was the case presented in Intelligence. The article is by professor Philip Vernon, also based -- another eerie one -- at the University of Western Ontario. It summarizes the latest findings linking IQ scores to activity in the physical brain, an organ indisputably acquired via hereditary processes. The link has been established in three kinds of research: (1) Studies done over many years, on groups ranging in size from a few individuals to hundreds, have measured the brain's ''average evoked potentials'' (AEP). The AEP studies measure electrical activity in the cortex and typically show significant correlations between the activity being measured and IQ scores. (2) Another promising, but expensive, line of research involves the use of positron emission tomography (PET) scans to measure the rate at which the brain metabolizes glucose while performing mental tasks. Because PET scans cost so much, the groups studied have generally been small. Still, the results are spectacular. They show that individuals who test high consume less cerebral glucose. In Vernon's words: ''Persons of higher intelligence can solve more (and more complex) problems during a given period of time . . . and expend less energy in the process.'' (3) Finally, there are tests of nerve conduction velocity (NCV), a field in which Vernon himself has been active. The NCV studies measure the speed with which electrical impulses are transmitted by the nervous system. Vernon mentions two studies, each involving around 85 university students, in which IQ scores correlated around 0.45 -- a quite substantial level -- with nerve conduction velocity. Like the glucose studies, the NCV data powerfully suggest that some people just have more efficient neural systems than do others. Might these data pacify the mob on Donahue? One wonders, does not one?