Developing Intelligence

What neural mechanisms underlie “fluid intelligence,” the ability to reason and solve novel problems? This is the question addressed by Gray et al. in Nature Neuroscience. The authors begin by suggesting that fluid intelligence (aka, gF) is related to both attentional control and active maintenance of information in the face of ongoing processing (i.e., working memory). Each of these concepts, in turn, has been associated with the functioning of the lateral prefrontal cortex – a region that has been massively expanded in humans compared to even our closest evolutionary relatives.

To confirm that individual differences in gF are related to prefrontal functioning, Gray et al. measured performance both on a standard gF task (Raven’s matrices) as well as on a standard test of prefrontal function from cognitive neuroscience: the 3-back task. In Raven’s matrices, subjects are required to pick which of several stimuli “fits” as the final item in a matrix of abstract patterns (see an example.) In contrast, the 3-back task provides subjects with a series of stimuli, presented sequentially, and requires that they respond if the current stimulus matches the one presented 3 items previously (i.e., to respond yes to the second “B” in a sequence like “A X B Y X B X A”). This task is performed in an ongoing fashion, such that subjects must constantly displace the third item in memory with the second, and update memory with the current item. (If you can’t tell from my description, this is an extremely difficult task).

Intuitively, one might not expect a strong relationship between these tasks: 3-back relies heavily on memory, whereas all the relevant stimuli are simultaneously present in Raven’s. Conversely, Raven’s requires abstract and somewhat “analogical” reasoning, but 3-back requires only rote memorization. So these tasks seem to require very different computations – an individual’s performance might be expected vary substantially between them.

On the other hand, there’s the concept of the “positive manifold”: performance on any two reliably-measured tasks is positively correlated (indeed, this is part of the basis for the concept of “general intelligence”). Surprisingly, the positive manifold may apply to neuroscience data as well: despite the possibility that different neural regions would underlie performance on these two very different tasks, certain regions in prefrontal cortex reliably mediate the behavioral correlations between these tasks.

To demonstrate this surprising fact, the authors distinguished between 3-back performance on lure trials (where the target item had occurred on perhaps the 2nd or 4th previous trial, but not the 3rd back) and those on non-lure trials (where target items occured on 1 trial ago, or more than 5 trials ago). Lure trials actually seemed more sensitive to performance than target trials (in which an item was actually presented 3 trials ago) insofar as accuracy was just as bad as target trials, but RTs were even longer.

Estimates of gF were positively correlated with accuracy on all trials types, but was most strongly related with lure trial performance: taking into account accuracy on non-lure trials or accuracy on target trials, gF still showed a significant relationship with lure trials. Activity in lateral PFC, anterior cingulate, and lateral cerebellum all predicted accuracy, and activity in these regions during lure trials overlapped with up to 92% of the shared variance between gF and 3-back performance. In contrast, this pattern was much more subtle on both target and non-lure trials.

Interestingly, the magnitude of sustained activation (thought to subserve active maintenance) was correlated with 3-back accuracy but not with gF ability. This finding is somewhat at odds with accounts that put “vanilla” active maintenance at the center of intelligence and executive control – other processes (such as those recall and discrimination processes involved in lure trials) appear to more strongly manifest the variance shared with gF. This would seem to have applications to the notion of “reactive control” and “secondary memory” as discussed recently in the literature – future work will need to clarify the relationships between these constructs.

The authors note that grey matter volume in lateral prefrontal cortex is under “significant” genetic control, suggesting that perhaps gF is itself largely heritable. Word has it that a new (but still under review) publication is showing the heritability of gF as being close to 1. In contrast, the authors here suggest that gF is probably not entirely heritable, and that a better understanding of individual differences in the neural correlates of gF could contribute to future attempts at enhancing fluid intelligence.


  1. #1 Robert
    May 6, 2007

    You can’t see the wood for the
    Intelligence, intelligent, from Latin intelligere understand (INTER+legere gather, pick out).
    Clever, Adroit, dexterous, skilful, talented.
    What do you mean by intelligence? What is the difference between being intelligent and being clever? Can a person be intelligent without being clever and visa versa? Hear are some definitions of intelligence.
    the ability to comprehend; to understand and profit from experience
    Intelligence is a general mental capability that involves the ability to reason, plan, solve problems, think abstractly, comprehend ideas and language, and learn. In psychology, the study of intelligence is related to the study of personality but is not the same as creativity, personality, character, or wisdom.
    Adaptability to a new environment or to changes in the current environment
    Capacity for knowledge and the ability to acquire it
    Capacity for reason and abstract thought
    Ability to comprehend relationships
    Ability to evaluate and judge
    Capacity for original and productive thought

    Of the preceding, the first definition with some addition comes closest to a good definition. That is the continuous desire and ability to comprehend and understand by observation and logical reasoning. Who is intelligent by this definition? The current IQ test has been used (with modifications) for over 100 years. The average IQ score is 100. An IQ score of 160 places you into the genius category and a score of >200 is categorised as unmeasurable genius. Computers are becoming ever more powerful and sophisticated. Is a computer intelligent? No, it will never be able to comprehend and understand. It might appear to do so but that will be an illusion. It will only ever be a programmed machine. Even if it is programmed to generate its own coding it will do so as an uncomprehending programmed manner. It will never think (I think, therefore I am). It will only appear to be as clever as the men or women that programmed it. If you do not comprehend and understand this then you are not intelligent (having understanding). There are young children (seven to ten years old) who have genius IQs of 160-170. They have above normal learning abilities and talents. However, like an autistic savant they are clever not intelligent. They see the world in a simplistic child like way. One of them may write music and play the violin to a professional standard. Another might be able to do complex mathematical problems. However, they do not have understanding. You would not expect complex philosophical insight and understanding from any one of them. The IQ test should be called the CQ test (cleverness quotient) for it has everything to do with measuring cleverness and nothing to do with measuring intelligence.
    We live on the thin crust of a sphere of molten rock and iron, which is nearly 8,000 miles in diameter. It moves at 18 miles each second through the black vacuum of space circling a star (the sun) which is 93 million miles away. The sphere has a thin layer of breathable atmosphere (less than 7 miles) and if it were not for the magnetic field generated by its iron core the radiation from the sun would be lethal to life. Only an intelligent person will comprehend and understand how strange, grotesque and bizarre this is.
    Many people use homeopathic medicine. Substances are diluted down to such an extreme level that nothing of the original remains. It is obvious that if nothing of the original source remains its only action on the body can be that of a placebo. An intelligent person will understand this fact but a clever person with the IQ of a genius might not. It is more than a 50% certainty that your death will not be pleasant. The percentage chance of you dieing peacefully in a bed surrounded by loved ones is not good. The reality is fear of dying, cancer, Alzheimer�s disease, painful infirmity, and all the indignities that come with old age. What intelligent person would want to bring another into this world with the near certainty of that happening?
    You cannot be mad and intelligent but you can be mad and clever.
    Many millions of people have a religious belief. That is the belief that there is an unseen intelligent all knowing, all understanding, all powerful, perfect in love entity who is the originator of everything here. It is obvious to an intelligent person that this is not true. The facts are not hidden. This world is extremely violent, dangerous and ugly and always has been. If there is a hidden unseen entity, it is obvious that it is malicious, evil and not intelligent. If you had a young child, you would not say �see how intelligent I am, I can do thousand of things that you cannot, love me, bow down, worship and adore me�. If you did so, you would be both mad and unintelligent. Yet that is how religious people view there God.
    An intelligent person would not think that a person who supposedly lived two thousand years ago could be his/her saviour by giving his life for them. The intelligent person would know that sin is subjective and that he/she does not need saving. An intelligent person would not believe that by blowing himself to pieces with the men, women and children in his vicinity he will be transported to paradise (by a just and loving God) and have beautiful serving females granting him his every sexual desire.
    By the same measure, it is unintelligent to accept a theory called evolution. The theory proposes that all mammals (including humans) evolved from a small mouse/shrew like creature that lived at the time the dinosaurs became extinct 65 million years ago. An intelligent person would want to know how and why he was here and would examine the theory, looking at all the evidence and paying particular attention to the time lines involved in that short period of 65 million years. The person who did not could not call himself intelligent. That person might be very clever and accomplished in many ways but would not be intelligent. If you are one of those you are not alone, you are legion.
    It is estimated that the human brain has approximately 100 billion neurons (100,000,000,000). You might think that this a very large number? If a neuron was equated to a computer byte that would be equivalent to 100 gigabytes. My PC has a storage area of 150 gigabytes. I take photos with my digital camera, which are 7 megapixels (7,000,000) in size. If you equated one neuron to one pixel, the total capacity of 7 megapixel photos my brain could hold would be 14,000 to 15,000. A neuron is only an organic non-thinking unaware cell that connects with many other neurons via chemical and electrical changes in its synapses. As you can see, 100 billion is not a lot for the equivalent of a simple on-off switch. How do these unthinking cells combine and make us sentient, conscious beings? And why is it that although there are no difference in everyone�s neurons some people are very clever and others are not? And why is there so little intelligence (understanding)?
    Imagine an intelligent visitor to this planet for the first time. What would he think after looking at its history and current situation? Elected governing representatives from different factions shout at each other like children. Countries ruled by unstable aggressive people. Millions dieing of starvation while billions are spent on unimportant pursuits. Men woman and children killed for reasons of race or religion in wars and internal conflicts. Countless women becoming pregnant and having abortions. A divide between a minority that are wealthy and the majority who are not. Pollution of the seas and exploitation of the land. The list would go on and on and on. The only correct conclusion possible is that the human race per se has no intelligence.
    Probably the most profound words in any language are �I think, therefore I am�. The man who said that also said �If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things�. The truly intelligent person examines himself/herself first. He then has the benchmark to question and examine others.

  2. #2 James Findlay
    October 2, 2009

    Fascinating the possibility of fluid intelligence. I prefer to call this fluid intelligence, play intelligence I view play intelligence as the core meta intelligence used in all human beings. That human beings learn best through play and that the brain is designed to play and is playing in a fluid state. My work is drawing interest from eminent Professors working with Intelligence such as Howard Gardner and Robert J.Sternberg. If you are interested I look forward to corresponding with you Chris on your work and share ideas.

New comments have been disabled.