It also should be remembered that brain-damaged patients taking standard IQ tests may have higher intelligence than the test score suggests. A standard IQ test requires visual perception skill (to read the test book) and finger coordination (to fill in the right answers using a pencil). Brain damage might cause reduced finger coordination and reduced visual perception unrelated to intelligence; and such things might cause a subject to do below-average on a standard IQ test even if his intelligence is normal.
The 1966 study here states, "Taken as a whole, the mean I.Q. of 95.55 for the 31 patients with lateralized frontal tumors suggests that neoplasms in either the right or left frontal lobe result in only slight impairment of intellectual functions as measured by the Wechsler Bellevue test." In this paper (page 276), scientist Karl Lashley noted that you can remove 50% of the cortex of an animal without having any effect on the retention of mazes learned by the animal. Lashley noted on page 270 of this paper something astonishing, that the smartest animal he had tested was one in which the fibers of the cortex had been severed:
Cognitive levels in many children do not appear to be altered significantly by hemispherectomy. Several researchers have also noted increases in the intellectual functioning of some children following this procedure....Explanations for the lack of decline in intellectual function following hemispherectomy have not been well elucidated.
Referring to a study by Gilliam, the paper states that of 21 children who had parts of their brains removed to treat epilepsy, including 10 who had surgery to the frontal lobe, none of the 10 patients with frontal lobe surgery had a decline in IQ post-operatively, and that two of the children with frontal lobe resections had "an increase in IQ greater than 10 points following surgery."
- Patients with local orbitofrontal lesions performed normally (at control levels) on three-decision making tasks.
- There was no statistically significant difference among the four frontal subgroups and controls on letter fluency or category fluency.
- Pattern recognition performance (percentage correct) was not significantly impaired in either the combined frontal group or the five subgroups.
- On spatial recognition (percentage correct), the combined frontal group were unimpaired relative to controls.
- On a gambling test to determine decision making, “The combined frontal group did not show poorer decision making than controls... and there were no significant differences among the five subgroups.”
There are, however, many new connections formed between brain cells. But an article at Neurosciencenews.com tells us the following:
|Prediction of theory that intelligence comes from brain, specifically the frontal lobe or prefrontal cortex||Reality|
|Injury to prefrontal cortex or frontal lobes should cause sharp drop in intelligence, as should hemispherectomy||This does not generally occur|
intelligence should not have increased since 1900, because there
has been no change in brain size or
|Since about 1930, IQ scores have risen by about 3 percent per decade (the Flynn Effect).|
|People about 70 should be much less intelligent than 20-year-olds, because of 5% volume decline in prefrontal cortex per decade.||Adjusting for Flynn Effect, no such drop in intelligence occurs.|
|Humans today should be much more stupid than humans 20,000 years ago, because our brains are smaller by about the size of a tennis ball.||Most people today would guess that humans are smarter, or at least as smart, as humans 20,000 years ago.|
|Elephants should be much smarter than humans, because their brains are three or four times heavier.||Humans are actually smarter than elephants.|
|Crows should be very stupid, because their brains are tiny, and have no neocortex.||Crows are astonishingly smart.|
|Greater number of connections in the brain should increase effective intelligence.||"The more intelligent a person, the fewer connections there are between the neurons in his cerebral cortex." -- neuroscience news cited above.|
|Men should be about nine percent smarter than women, because their brains are about nine percent bigger.||It is generally recognized that on average men are not significantly smarter than women.|
|Adults should not be much smarter than babies or toddlers, because they have no more brain cells than babies or toddlers.||Adults seem to be much smarter than babies and toddlers.|
Postscript: In 1930 a patient listed as Joe A. in the medical literature underwent a bilateral frontal lobectomy performed by Dr. Walter Dandy, who removed almost all of his frontal lobes. An autopsy in 1949 confirmed that "both frontal lobes had been removed." The paper describing the autopsy said that from 1930 to 1944 Joe A.'s behavior was "virtually unchanged." On page 236 of this source, we read that Dandy said this of three patients including Joe A.: "These three patients with the extirpation of such vast areas of brain tissue without the disclosure of any resulting defect is most disappointing." I could see how it would be disappointing for someone hoping to prove a connection between some brain area and intellectual function. Page 237 of the same source tells us that on casual meeting Joe A. appeared to be mentally normal. Page 239 of this source states this about Joe A, summarizing the findings of Brickner.:
Nor was intellectual disturbance primary. The frontal lobes played no essential role in intellectual function; they merely added to intellectual intricacy, and "were not intellectual centers in any sense except, perhaps, a quantitative one."
A 1939 paper you can read here was entitled "A Study of the Effect of Right Frontal Lobectomy on Intelligence and Temperament." A patient C.J was tested for IQ before and after an operation removing his right frontal lobe. He had the same IQ of 139 before and after the operation. Page 9 says the lobectomy "produced no modification of intellectual or personality functions." On page 10 we are told this about patients having one of their frontal lobes removed:
If the frontal cortex is some kind of "seat of reason," we might expect the human frontal cortex to be unusually large for a primate. But the paper here states, "The consistency of our results across independent data sets supports the view...that human frontal cortex, and regions and tissue subtypes within it, are no larger than expected for a nonhuman primate of our overall cortex or brain size."
The following excerpt from a scientific paper tells us of additional cases of people who did not seem to suffer much mind damage after massive damage to the frontal lobes or prefrontal cortex. Resection is defined as "the process of cutting out tissue or part of an organ."
Several well-documented patients have been described with a normal level of consciousness after extensive frontal damage. For example, Patient A (Brickner, 1952) (Fig. 2), after extensive surgical removal of the frontal lobes bilaterally, including Brodmann areas 8–12, 16, 24, 32, 33, and 45–47, sparing only area 6 and Broca's area (Brickner, 1936), “toured the Neurological Institute in a party of five, two of whom were distinguished neurologists, and none of them noticed anything unusual until their attention was especially called to A after the passage of more than an hour.” Patient KM (Hebb and Penfield, 1940) had a near-complete bilateral prefrontal resection for epilepsy surgery (including bilateral Brodmann areas 9–12, 32, and 45–47), after which his IQ improved. Patients undergoing bilateral resection of prefrontal cortical areas for psychosurgery (Mettler et al., 1949), including Brodmann areas 10, 11, 45, 46, 47, or 8, 9, 10, or 44, 45, 46, 10, or area 24 (ventral anterior cingulate), remained fully conscious (see also Penfield and Jasper, 1954; Kozuch, 2014; Tononi et al., 2016b). A young man who had fallen on an iron spike that completely penetrated both frontal lobes, affecting bilateral Brodmann areas 10, 11, 24, 25, 32, and 45–47, and areas 44 and 6 on the right side, went on to marry, raise two children, have a professional life, and never complained of perceptual or other deficits (Mataró et al., 2001).
Apparently patient KM got smarter after they took out most of his prefrontal cortex. That's a case helping to show that brains don't make minds. The book here discusses intelligence tests done on patients who underwent surgery on the frontal lobes:
"It was natural that the effect of an injury on the frontal lobes, said to be concerned with the higher functions of men, should be measured by these tests of intelligence. The absence of marked effects on mental ability, as measured by these intelligence tests, was, not surprisingly, felt to be puzzling."
This paper here describes a case of a "modern Phineas Gage": a patient C.D. who suffered massive prefrontal damage after a penetrating head injury. But C.D's IQ after the injury was measured at 113, well above average. His verbal IQ after the injury was 119, in the 90th percentile. We read:
C.D. reported that he did not have any cognitive or emotional problems following the accident. In describing how his thinking skills were completely unaffected, C.D. stated that, "all the shattered bone was caught in the gray matter in front of the brain."
The paper also tells us, "C.D.’s performances on memory tests were all in the average to above-average ranges in terms of the traditional measure of level of correct responses."
Using the term "decorticate" to refer to animals that had their cortex surgically removed, the scientific paper here tells us that rats and cats seem to show relatively little behavioral effects when you remove their cortex:
"All of the behaviors just mentioned are also exhibited by experimental animals after their cerebral cortex is removed surgically, either in adulthood or neonatally. Best studied in this regard are rodents (Woods 1964; Wishaw 1990). After recovery, decorticate rats show no gross abnormalities in behavior that would allow a casual observer to identify them as impaired in an ordinary captive housing situation, though an experienced observer would be able to do so on the basis of cues in posture, movement and appearance (Whishaw 1990, on which what follows relies, supplemented by additional sources as indicated). They stand, rear, climb, hang from bars and sleep with normal postures (Vanderwolf et al. 1978). They groom, play (Pellis et al. 1992; Panksepp et al. 1994), swim, eat, and defend themselves (Vanderwolf et al. 1978) in ways that differ in some details from those of intact animals, but not in outline. Either sex is capable of mating successfully when paired with normal cage mates (Carter et al. 1982; Whishaw & Kolb 1985), though some behavioral components of normal mating are missing and some are abnormally executed. Neonatally decorticated rats as adults show the essentials of maternal behavior which, though deficient in some respects, allows them to raise pups to maturity. Some, but not all, aspects of skilled movements survive decortication (Whishaw and Kolb 1988), and decorticate rats perform as readily as controls on a number of learning tests (Oakley 1983). Much of what is observed in rats (including mating and maternal behavior) is also true of cats with cortical removal in infancy: they move purposefully, orient themselves to their surroundings by vision and touch (as do the rodents), and are capable of solving a visual discrimination task in a T-maze (Bjursten et al. 1976; see also Bard & Rioch 1937)."
"Forty-eight percent of the sample did not show decline on any of the 16 cognitive measures examined in this study. Forty-two showed decline on measures in 1 or 2 cognitive domains. In contrast, 10% of the sample showed declines in 3 or more cognitive domains."
Elsewhere the paper states, "The vast majority of patients who undergo frontal lobectomy for treatment of pharmacoresistant epilepsy demonstrate good cognitive and motor outcomes." Using the term "frontal lobectomy" for the removal of the front part of the brain, the paper also states, "Interestingly, there was a subset of patients who demonstrated clinically meaningful improvements in confrontation naming (15% of sample), verbal intellectual function (11%), or memory (10%–17%) following frontal lobectomy." The paper says, "Existing studies that have examined change in intellectual functioning following frontal lobe surgery have had mixed results, with some studies reporting no change on intelligence measures and others reporting apparent improvements.""