Do Frontal Lobes Mediate Intelligence

1. DO FRONTAL LOBES MEDIATE
INTELLIGENCE
Dr.M.Ramya Maheswari
Asst Prof & Head
Department of Psychology
Ethiraj College For Women

2. INTRODUCTION
Since Hebb’s (1939, 1941, 1945) devastating reviews of the role of the frontal lobes in intelligence – he concluded that there
was not much of one – frontal lobe function and conventional intelligence have not been strongly associated.
Warrington et al. (1986), for example, administered the Wechsler Adult Intelligence Scale (WAIS) battery to 656 patients
with either unilateral parietal, temporal, occipital or frontal lobe damage and reported similar scores for each patient groups.
Some frontal lobe patients perform very well on standard ‘intelligence’ tests.
However, Duncan and his colleagues (Duncan, 1995; Duncan et al. 1995) propose that frontal lobe function is related to
intelligence but not to conventional, general intelligence, or g. Instead, Duncan proposes that the frontal lobes might be
involved in the execution of tests of fluid intelligence: that is, tests that do not require the subject to use prior information
explicitly.
Duncan found that three of the frontal lobe patients he studied performed well on the WAIS but were poor on the Multiple
Errands Task. However, on tests of fluid intelligence, such as Cattell’s Culture–Fair Test, the patients’ IQ scores were 22–28
points lower than their WAIS IQs.

3. TESTS OF FLUID REASONING
Furthermore, their Culture–Fair IQs were 23–60 points lower than those of normal controls. This study suggests that when
g is measured by tests of fluid intelligence, frontal lobe integrity is important for successful performance. If tests are
tapping crystallized intelligence, the frontal lobes appear to be no more or less involved than other lobes.
An early PET study indicated that individuals with high IQs had lower metabolic rates than those with low IQ during
problem solving (Haier et al. 1988).
When high- and low IQ individuals were trained on a computer game, both groups’ brain activity declined, but the decline
in the high-IQ group was more rapid, suggesting that the highly intellectually able may need to use less of their neural
machinery to think (Haier et al. 1992).
The less effort hypothesis also receives some support from EEG studies. High-IQ individuals show consistently higher
EEG alpha power (that is, less mental effort) during problem solving and preparation for problem solving than do low IQ
individuals (Jausovec 1996). The most pronounced differences between high- and low-IQ individuals during working
memory and arithmetic tasks was found across the frontal regions (Jausovec 1998).

4. DECISION MAKING
Antonio Damasio and colleagues’ studies of patients with frontal lobe damage suggesting that these individuals have great
difficulty in making correct decisions (Damasio 1995; Bechara et al. 1996, 1997).
Damasio suggests that the ability to make decisions leading to positive or potentially harmful consequences depends on the
activation of somatic (that is, bodily) states. Damasio calls this the somatic marker hypothesis, because such decisions involve
automatic, endocrine and musculo-skeletal routes. These routes mark events as important but appear to be impaired in certain
frontal lobe patients.
For example, patients with damage to a specific area of the prefrontal cortex are unable to make decisions in real life despite
having intact cognitive ability. When the decision can have a positive or negative outcome, the degree of physiological
activity commonly seen in healthy individuals when they make such decisions is absent in these patients (Bechara et al.
1997).
In one study, frontal lobe patients and healthy controls were taught to play a card game, the Iowa Gambling Task, in which
they were required to make as much money as possible . There were four decks of cards, and some had a high probability of
delivering a large immediate monetary reward or a large delayed monetary loss or a low immediate monetary reward or a low
delayed monetary loss. No participant was told which deck contained the greatest probability of obtaining these outcomes,
and they therefore had to learn from experience, turning over cards and remembering the outcomes. They had hunches.

5. DECISION MAKING
For example, when a decision involved a high degree of risk (such as losing a large amount of
money), a healthy individual would show a characteristic increase in physiological arousal but the
frontal lobe patients would not. The patients would show a characteristic response after they had
lost or gained, as would controls, and all patients were aware that they had lost money.
In imaging studies, performance on the gambling task is associated with increases in blood flow to
the ventro-medial region of the frontal cortex (Elliott et al. 1997; Grant et al. 2000). Bechara et al.
(2000) were interested in determining whether these patients behaved in the way that they did
because they were hypersensitive to reward, were insensitive to punishment or were insensitive to
future consequences.
It was found that the group found that the VM patients failed to be sensitive to future
consequences. Instead, they seemed to be guided by immediate reward.The researchers call this
‘myopia for the future’.The researchers call this ‘myopia for the future’. Even when the future
consequences of behaving in a particular way are undesirable, these patients continue to behave in an
inappropriate way.

6. DECISION MAKING
Manes et al. (2002) argue that although studies have ostensibly shown deficits in the gambling task in patients with
frontal lobe damage, this damage is not restricted to the frontal cortex but extends beyond it. In Bechara et al.’s (1996,
1997) studies, for example, lesions were found in the medial orbito-frontal region but extended to the dorso-lateral cortex
and other neighbouring regions.
Manes et al. (2002) studied the effects of restricted orbito-frontal cortex, dorso-lateral, dorso-medial and large frontal
lesions on a variety of neuropsychological measures, including the Iowa Gambling Task and a version of this designed to
increase the sense of risk. They found that dorso-lateral lesions were associated with working memory, set shifting and
Iowa Gambling Task impairments; dorso-medial lesions were associated with planning and Iowa Gambling Task
impairments; and orbito-frontal lesions were associated with performance at control level, but patients showed prolonged
deliberation on the Tower of London task, a task that required forward planning. However, the group with large frontal
lesions showed great impairment and was the only group to show risky decision making. According to Manes et al.’s
criteria, patients in the Bechara studies would be classified as having large frontal lesions.
Fellows and Farah (2005) have also reported that ventro-medial and dorso-lateral cortex damage can cause impairment
on the Iowa Gambling Task. These results suggest that the size of the lesion may be the critical predictor of risky
decision making: both the dorsal and ventral parts of the prefrontal cortex need to be damaged before impairments are
observed.

7. REASONING
If the frontal lobes are important for reasoning, then we could predict activation in these areas when
healthy individuals perform a reasoning task during neuroimaging.
Goel et al. (1997, 1998) reported two experiments in which they sought to test this hypothesis. In one
experiment, they asked ten participants to undertake inductive and deductive reasoning tasks. These
involved syllogistic reasoning tasks such as deciding whether the following logic was correct:
All carpenters are young.
All woodworkers are carpenters.
All woodworkers are young.
and
George was a woolly mammoth.
George ate pine cones.
All woolly mammoths ate pine cones.
The experimenters found that the frontal lobes were involved: significant increases in activation were
reported in the left inferior and middle frontal gyri.

8. REASONING
But reasoning appears to be dissociable in that the type of content in a reasoning task
affects how well people reason. When given a task where the content is familiar (e.g. all
apples are red fruit; all red fruit are sweet; therefore, all apples are sweet), people perform
such syllogisms better than if the content is not familiar and more formal (e.g. all A are B;
all B are C; therefore, all A are C).
The former example seems to be associated with increased left frontal activity, whereas
the latter is associated with increased bilateral parietal activity with some evidence of
prefrontal activation. Based on this evidence, Goel et al. (2004) reasoned that focal lesions
in the left frontal cortex would have a more detrimental effect on a reasoning task that
involved familiar content than one where the content was more formal. They appear to be
more involved in reasoning that requires people to understand socially pertinent
information.

9. REASONING
As inductive and deductive reasoning are distinct psychological processes, we might expect
different regions of the brain to be recruited when people perform the two types of reasoning
task.
One fMRI study found that both tasks activated the left prefrontal area but also bilateral regions
of the frontal, parietal and occipital cortices (Goel and Dolan 2004). There was some evidence
of a dissociation, however. The deductive task was associated with greater activity in a region
called the left inferior frontal gyrus, whereas the inductive task was associated with more
activity in the left dorsolateral prefrontal gyrus.
Broca’s area, in addition to its traditional function, is also involved in working memory and in
processing syntax – two activities involved in deduction. Inductive reasoning relies on less
logical forms of thinking and relies on the person’s background knowledge. The authors point to
studies showing how dorso-lateral lesions in patients result in deficits in everyday reason