part 1
Nereid said:
Indeed, all parts of the brain would seem to be related to biology, which is partly why I'm quite puzzled that there is, AFAIS, no biological theory of intelligence.
Mandrake: I don't understand your observation. What do you think would constitute a biological theory of intelligence? How does that differ from existing models?
Nereid: If you're referring to the nice stamp collection of 'biological correlates', then that hardly constitutes a 'biological theory.'
If you think a stamp collection is a fair analog to the information known in the field of psychometrics, you might want to reconsider. Stamps in a collection do not tell us anything about other stamps. They do not fit together to show an overall picture. Psychometrics is a science and the knowledge base that it has produced over 100 years is extensive. Just as in any other science, the big picture continues to clarify as investigational tools improve. Consider what has been found in astronomy in the past 50 years. Things progressed slowly until deep space probes and Hubble suddenly provided mountains of new information. Psychometrics is now benefiting from sophisticated laboratory instrumentation and techniques. A better (but still low quality) analogy would be that the individual pieces of information in any science are somewhat like the pieces of a jigsaw puzzle. The shape of one gives us a hint about the shape of another. When joined, the image from several pieces is additive.
Perhaps this succinct statement is closer? "Jensen (1993), as well as others, synthesized these facts and conjectured that "the most obvious hypothesis is that speed of information processing is the essential basis if _g_, and one possible neurological basis of speed of processing is the speed of transmission through nerve pathways" (p. 54).
I happen to be familiar with the source of this comment, but it does not appear on page 54 of the paper that I know in which he presented his hypothetical model. What is the source you have in mind? Why did you give the year, but nothing else? Jensen published several things in 1993. Will you please give the full reference?
The speed of information transmission can be reasonably well measured or extrapolated from reaction time scores. Therefore, if an individual has faster neural processing speed, then he or she have a better reaction time. In turn, given that reaction time is highly correlated with IQ, then those individuals with faster neural processing speeds have higher IQ's. Consequently, neural processing speed determines the level of intelligence of the individual; this intelligence is the one general intelligence, _g_." If so, then where are the studies which show that estimates of _g_ correlate with well known factors affecting reaction time (e.g. drowsiness, illness, drunkeness)?
What? Do you think that scientific research in psychometrics is conducted by idiots? Do you really think that they include subjects who are impaired by obvious factors? I am amazed by this comment. What is your reason for this? Have you ever read papers on chronometric measurements? I am absolutely in disbelief that you cannot separate mental impairment with the foregoing comments.
There may be some special interest in RT as it pertains to impaired people, but most examples I can think of would include MT.
Similarly, one would expect that those who are good at pingpong, or fencing, would have elevated _g_ (reaction time is a key factor in excellence in these sports); and that southpaws smarter than normal folk.
You are badly confused.
RT measurements are typically based on a simple laboratory apparatus, which consists of a home button and multiple response buttons.[1] The device used by Jensen consists of a home button and 8 response buttons, arranged at equal distanced from the home button in an arc of 180 degrees.[2] Each response button has a light directly above it (or, in later devices incorporated lighted buttons). The person being tested holds the home button down and then must press the button closest to the light that is illuminated as the “external stimulus.” The measurement device records the time the stimulus lights goes on; the time the home button is released; and the time the response button is pressed:
T1 ………. T2 ………. T3
The time interval from T1 to T2 is the reaction time, RT. The time from T2 to T3 is the movement time (MT).[3] This simple test is an example of an Elementary Cognitive Task (ECT) and can be completed by any adult (even with IQs as low as 15 to 20), usually in less than 1 second. Individuals with IQs below 40 require some acclimation to the test. Jensen’s tests covered individuals from IQ 15 to 150. There is essentially no correlation between MT and intelligence.
[1] Multiple response buttons are used for reaction time testing known as choice reaction time. There is an IQ correlation to even the most elementary RT testing, known as simple reaction time. Simple reaction time is measured by having the test subject release a button when he is presented with an external stimulus. Discrimination reaction time is a variant of simple reaction time which also uses one button, but requires the test subject to release the button only when the stimulus matches a predefined condition.
[2] Other researchers have used the same measurement devices. The topic of RT testing is discussed at length in numerous places. Bias in Mental Testing is now nearly a quarter of a century old, but has a good discussion. For a more recent reference, see The g Factor.
[3] Some psychometricians define RT as the total time from the start of the test to the end and divide that time into two components, designated “decision time”(DT) and MT. In this case, RT = DT + MT. Jensen designates RT as the first component and does not bother to discuss the sum.
The thing you are describing is MT.
However, a biological theory of intelligence should do more than just conjecture;
A theory resides (among scientists) between a hypothesis and a natural law. An example is the Theory of Relativity. An example of a law is Ohm's Law. It is, in my opinion, scientifically incorrect to imply that a hypothesis is a theory. At present, we have good understandings of various components of intelligence, such as the fact that the variance in the speed of information intake is fundamental to the variance in intelligence. Your quote ignores that we also know that the standard deviation of RT correlates negatively to _g_ and that this correlation is independent of the mean RT correlation. I have never seen a single explanation as to why both happen. It is apparent that there are two factors at work (working memory efficiency and neural noise).
If you are interested in another model of information processing (besides the one Jensen reported in 1993), please see Figure 3 in Chapter 4 of Brand, C. (1996). The _g_ Factor: General Intelligence and Its Implications. Chichester, England: Wiley.
