Nature, nurture, and evolution:

A discussion of the significance of genetics and evolution for understanding human behavior

Senior Seminar in Neural and Behavioral Sciences
Bryn Mawr and Haverford Colleges, Spring, 2002

Session 3: The Genetics of Intelligence
(Readings and Web Links)

Name:  Rebecca Roth
Subject:  intelligence
Date:  2002-02-19 19:16:52
Message Id:  1083

What is intelligence? Is our intelligence determined when we are born or is it the result of interactions between our heredity and our environment? Is intelligence really one thing or is it a variety of things? There are many different conceptions of intelligence. Intelligence could be defined as the capacity to learn from experience. It could also be an adaptation to one's environment. Various psychologists have/had strong views on intelligence (e.g. Piaget). If you take a cognitive psychology class you would learn that there are two types of intelligence: fluid and crystallized intelligence. Gardner developed a multiple intelligence theory (Linquistic, musical, logical-mathematical reasoning, spatial, bodily-kinesthetic, interpersonal; and intrapersonal). This is thereby showing that there are many different factors that can account for intelligence. It is obvious that no one can excel in all areas. Afterall, no one is perfect. The definition of intelligence, genetic influences, and validity and reliability of intelligence tests should be analyzed further. Intelligence to me is being a well-rounded individual. Intelligence is not just having 'book smarts', but also having social skills.

A problem with looking at what influences intelligence, whether it is genetics or the environment, is that generally people related to one another live together. Therefore, it is sometimes hard to differentiate if it is really genetics or if it is in fact the environment. Intelligence is not all genes. I would say that genes influence intelligence, but certainly cannot determine intelligence. Both genes and the environment interact with one another. This is what leads us to be unique individuals. Genetics and the environment both are factors in intelligence. There has to be a genetic component of intelligence, according to twin studies. Some adoption studies show that environment plays a factor in intelligence.

The exploration of the genetics of ‘intelligence’ is useful. Genetics could be used to show the connection between different traits and behaviors. Learning and memory are at different stages. Does Ginko really improve our intelligence? There will always be a search for drugs that can help us improve our memory and make us more intelligent. It was interesting to read that the “gray matter in the frontal lobes turned out to be correlated with intelligence.”

There is variability which cannot be accounted for. More studies and observations need to be done to develop a greater understanding of what 'intelligence' actually is. More people need to be looked at who live in the same environment (household), but are not genetically related to each other (adoption). Even though environmental factors could lead family members to be different. We act differently in school, than we do when we are at home with our parents. Many variables need to be looked at such as the relation between IQ and academic achievement.

Why is it that people say first born children are smarter? Is this really true? If intelligence was strictly genes, all the parent's children should be about the same 'intelligence'. Stressful events, parental perspectives, health, family size, socio-economic factors, social multiplier effect, all can influence ‘intelligence’.

Performances on IQ tests are malleable. It is one test given on one day, that in some cases (standardized tests) can affect where you go to school. I think the environment definitely affects ones performance. The environment in which you take tests does make a difference. That is why some people recommend studying in the same room that you are going to be taking the exam in. For instance, I took countless number of LSAT exams, some were in my room, and some were at the Kaplan center. I consistently did extremely well on all the practice exams and when it came to the actual exam, being in the exam room, knowing that this was the test that really counted, my score changed and I no longer got the score I was getting on the practice tests. If it was strictly genes, I should have gotten a 99 percentile on the LSAT exam, or somewhere around there. But I didn't. Or should I have not gotten the same range? What exactly are prep tests teaching? They never helped improve my score--are they really teaching you how to take the exam, or are they teaching you “how to beat the test”? I agree with Professor Grobstein in that “failure to perform well on standardized tests indicates failure to perform well on standardized tests. Period.” I think it is unfortunate that so many colleges and grad schools look so much at standardized tests. Granted standardized tests are standard, so that it is the only way to judge everyone, since different schools grade differently and people take various courses. But there is such a strong emphasis on standardized tests. I know that the LSATS count for about 70%. One of my friends scored phenomenally on the LSAT and had a 'low' G.P.A. However, he got into a top law school, and did terrible in law school. He is a good lawyer, though. He is still one of the smartest people I know, regardless of his G.P.A. in undergrad and in law school. Are the standardized tests really showing that he really is intelligent? What about his grades in school? And what about him not applying himself in school, is that considered ‘intelligent’m not using your full potential (according to the test) ? What about people on the other end of the spectrum—scoring terrible on standardized tests but having a 'top' G.P.A. in college and in grad school? As far as tests in general go, I think it matters how well you can perform under pressure. What kind of day you are having can affect your perfomance. If new tests come about, there needs to be tests which assess a broader range of intellectual abilities. Is it that IQ/standardized tests are really instruments of political and social control?

Name:  caroline
Subject:  intelligence: fact or fiction
Date:  2002-02-26 23:16:49
Message Id:  1236
In practical, concrete terms, use of the word "intelligence" is about as meaningful as "consciousness" (to bring us all back to last semester's conversations). In the case of both words, it is likely that there won't be many people who don't have some kind of working knowledge and understanding of the concept. However, attempting to pin down an exact description of what that word entails in realistic terms may prove more elusive. The vague definition of what intelligence means connotes a level of "smarts," most often referring to an academic context. That is regularly and intrusively quantified based on standardized tests, and applied as an all-inclusive label of how intelligent you are. This may serve to either open endless doors of opportunity, or it may be a limiting factor. There seem to be definite inequities in the current system. First of all, the knowledge needed to succeed on standardized tests is specific and biased. Second of all, they test what you know at that minute on that day, and leave no room for what you may continue to learn, or for what you tried unsuccessfully to learn in the time leading up to the test. The standardized tests are not an accurate reflection of a person's particular strengths and weaknesses. Rather, they test your ability to fit into a predetermined and culturally constrained mold. True intelligence must be recognized as having many facets. Genetic and environmental factors contribute to what strengths a person has and how they are expressed. The debate about which of those influences may take precedence, if indeed one could be definitively identified as doing so, is not one that will be easily resolved. However diffuse intelligence may be as a concept, patterns of strengths can easily be identified within families. These abilities may take any form - academic, artistic, athletic - but it cannot be denied that there tend to be distinct family resemblances in skills and interests. Having acknowledged this, it would also be reasonable to conclude that the parents' own passions leave some distinct impression on their offspring. At the same time, there are countless examples of child geniuses or virtuoso violinists coming from families with only "average" ability in those areas. This concept of the "average" seems in and of itself problematic, and is worthy of consideration. The very act of assigning a label must have some meaningful impact on the performance of the recipient of that label. Numerous studies have been done to assess the consistency of difference among different ethnic groups in terms of academic performance. Most often, it comes down to drawing distinctions among African Americans, Caucasians, and Asians. It is proposed that Asian students perform on such a high level because of the style in which they are taught. Rather than viewing information as something that can only be "gotten" if you possess a certain aptitude, these students approach their studies with the initial assumption that all are equal, and all are equally capable of academic success. This eliminates the categorization that is so rampant in American schools. The opposite argument can be made for the, in very general terms, lower level of performance observed among African Americans. They, as an ethnic group, perceive themselves to be disadvantaged. And, putting aside the truth to that claim, this likely has a deleterious impact on how they approach school. In view of all this, it seems as though intelligence is a most relative term. All this points to there being definite enviromental and psychological factors at play in how a person manifests their personal intelligence. The educational context to which a person is exposed, the support a person receives from his or her family both emotionally and financially, the social support and opportunity a person is given, all influence the trajectory of a person's so-called intelligence. But it is also important that intelligence, in the sense of ability or skill and trying to avoid a strictly academic meaning, is not so much on a continuum that a person with only mediocre natural ability might eventually excel at the highest level after being exposed to a more enriched environment. There must be natural limits on how much a person can realistically succeed at a given endeavor, as imposed by genetics. The difficulty will come in striking a balance between a person's natural aptitude for a task and the environmental influences that may alternately impede or augment that ability.
Name:  ingrid
Subject:  2 main concerns
Date:  2002-02-26 23:30:02
Message Id:  1238
I have two major problems with looking for the gentics behind intelligence. One would be that we haven't even figured out what intelligence itself is. We're not sure if it's logico-linear, visual-spatial, art or music, calculus or language. Different things are valued in different communities. This is not just concerned with the whole 'standardized testing' thing, but what has been considered advantageous or 'intelligent' in a community at large. I can very easily see aspects of advancement differ from culture to culture (or at Least coninent to continent). What is intelligence anyway? If we can't figure out what it is, then can we figure out what it is meant to do? If not the cause than the effect? I don't even think we've come that far.

Second is that, without this definition, we're not even sure what we're looking for in the brain. What lights up on a brain scan during a task may be decieferable. But what task do we give the individual? And is that applicable to what his 'intelligence' will be used for in all real life situations? How about the difference between intelligence and street-smart wisdom? I find people who are socially inept, wity, sarcastic, and have a good sense of direction to be more 'intelligent' than someone who can recide shakespeare's plays in a time of crisis. Can we measure all these factors at once? We've barely mapped out the regions in the brain, and certainly what we Have done isn't so specific as 'intelligence' (whatever that may be).

Heritibility in brain differences in general is actually very interesting. And may lead us somewhere. But were we expecting anything different? If any of our behavior at all is somewhat heritble then I believe that our question has already been answered: yes, then things in our brain are heritible too.

One thing I did find fascinating is the method behind the mouse genetics. The fact that they can snip out a piece of DNA (including the 'on' tag), put it in the nucleous of a forming cell, and have it used.... i just find that absolutely incredible. Am I correct in predicting that this can be done in humans as well? Because mice aren't 'so much' of a 'lower animal' in the kingdom.

And though this question implies that I may think that humans are alterable, I don't necessarily believe that we will be able to change anything in our behavior so easily through gene therapy. My main concern with this is that the same chemicals do different things through different parts of our brain. To use just an easy example, we can't just modify or remove dopamine protein synthesis in cells and expect to fix something like schizophrenia. However, We would have to be able to express (genetically) that dopamine receptors in certain regions specifically need to be adapted or changed. And probably even more specific than that. But all in all, if 'we' can come out of the codes in a single cell, then I'm betting that how ever many codes are needed in order to specify one little operation, the codes Are in there. or maybe modifiable?

Name:  hiro :)
Date:  2002-02-26 23:44:50
Message Id:  1239
I totally agree that IQ tests do not measure one's "intelligence" accurately. i actually took the sample IQ test in Carey (2000), and as he has hypothesized about non-Americans, I could not come up with the sentence, "a stitch in time saves nine" because I have never heard of the aphorism before. And, i strongly agree that this situation shouldn't mean that i lack "intelligence" because it was such a cultural question.

the same ideas can be applied to the academic grades. i was born and raised in japan, and when i was 15, i was thrown into a high school in california that had no ESL (english as second language) programs. of course, my first trimester grades were very low because i couldn't even understand what my teachers were saying or what the tests were asking me to do! (gosh, that was hard!!!) and it didn't mean that i was dumb. if i took the same subjects taught in japanese, my grades would have been a lot higher (of course, it might have depended on how much my teachers liked a trouble maker like me, too...).

Plomin & DeFries (1998) has mentioned dyslexia as if reading disability is a lack of intelligence, but i disagree. it is true that students with dyslexia have a very hard time academically. however, they show their "intelligence" in different fields. for example, i have a dyslexic friend who is a phenomenal basketball player. he has the most number of assists in his league because he can learn quickly about the playing styles of his teammates and opponents. and he gives different kinds of passes to different players, considering where his teammates are, who is playing well that day, where the opponent players are, what kind of rhythm the team needs at that time, etc, and makes the best decision in a very limited amount of time. although he may not be "smart" in the classrooms, i believe that his ability to succeed in basketball in such a way makes him an "intelligent" person, too.

if "intelligence" is realted to learning and memory as suggested in Tsien (2000), the amount of gray matter will not necessarily reflect one's intelligence. i agree that having more neurons increases the possible cell-to-cell connections. however, in order for the memory/learning to take place, the synaptic connections must strengthen. so, even if a child inherits some genes coded for producing a bigger gray matter, if he does not have an efficient amount of NMDA receptors or calcium transporters (which probably are also genetically determined), he will not be able learn or memorize quickly. on the other hand, if a person has a small gray matter but still has a very efficient NMDA system, he will be able to memorize and learn fast and be "intelligent".

people show "intelligence" in different areas, such as language, math, sports, music, art, etc. i believe that this phenomenon results from individual difference in brain structures. i think that one's brain has a highly developed memory/learning system in a certain area (like a part related to music or art abilities), causing the person to show "intelligence" in that particular field. and genes play an important role in determining which brain part(s) become highly developed.

Name:  Huma
Subject:  g
Date:  2002-02-27 00:25:10
Message Id:  1240
In our everyday encounters, intelligence matters. I’m not sure of the usefulness of the term general intelligence (g) or IQ tests, but the concept itself is undeniably important. Intelligence affects how one communicates, thinks, problem solves, and lives.

There are multiple factors that affect one’s intelligence; genetics is one of these factors. If we want to know what intelligence is, then it is necessary to determine how much influence each factor has on it. The most frequent statistic regarding the heritibility of intelligence is that genetics account for 50% of intelligence. The Wade article suggests a link between intelligence and the size of some regions of the brain that are under tight genetic control. However, it does not address what came first the size of the gray matter or the intelligence? This article leaves me unconvinced and seems reminiscent of phrenology. Though I found the Thompson article on the genetic influences on brain structure to be more convincing, it brought to mind the discussion on height that we had during the last class. Again, it seems that great variations can occur within families. This supports the idea that genes determine a range and where one falls within that range is under the influence of environmental factors. An important point that Plomin and DeFries make is that the collaborative genes that affect cognition do so in a probabilistic rather than deterministic manner. This parallels the idea of “the range” as well as Carey’s “indolent gatekeeper” analogy. I agree with Carey that IQ has the potential to open many doors, however, this not guaranteed, and the other factors such as motivation and interest have a great deal of influence on one’s success in life. I really like this quote by psychologist Robert Sternberg in response to The Bell Cure, “How strange that we have become a society that values what someone might do more than what he has done."

The study of the genetics of intelligence is not always desirable as it has the potential to lead to unfair assumptions and discriminatory behavior. Therefore, it is important to question the research that is being done. Hernstein and Murray, authors of The Bell Curve, led many to believe that immigrants would bring down the average IQ of our society and that measures should be taken to stop this. This differs from Tsien’s work on the NMDA receptors in Doogie mice that led to greater memory and long-term potentiation. Tsien’s work may have useful practical applications such as preventing cognitive decline while Hernstein and Murray’s work is based on numerous correlations and has questionable applications.

I have several uncertainties about the intelligence issue. Although I feel that there may be some beneficial results of research such as Tsien’s, I’m also weary of its potential use in genetic engineering. Inevitably,many will view this line of research as a means to increasing the general intellect of society. However, there is a need for people of varying IQs, each person serves a role in society appropriate to their intellect. In other words, how many rocket scientists does a society need?

Name:  jimmy
Subject:  Intelligence
Date:  2002-02-27 00:26:58
Message Id:  1241
Intelligence is a meaningful term provided that we don’t look into it too much. What I’m trying to say is that we all have a general understanding of the word and as long as we leave it at that we can more or less have decent conversations about it. The usefulness of this type of definition, however, is very limiting because perhaps we don’t know what each other is specifically referring to when we say “intelligence.” Carey speaks to this type of concept when he talks about ideas like multiple intelligences.
I like to talk about intelligence often in terms of memory and learning simply because you can failry consistently study those concepts quantitatively especially in mice. I loved the idea of targeting the NMDA receptor subunit molecule NR2B. It seems like a reasonable target for improving memory in people as they get older.
It also makes me wonder about the molecules underlying the amazing memory of Luria’s patient S. who was a remarkable mnemonist. S. had such a memory that he could remember a list of a hundred years literally 15 years after being presented the series even if he wasn’t told that he would be tested on it years later. The way his mind worked however, was vastly different than the normal person. When he heard a word or saw a number in a list, he would see an image of the word. So if he saw a “2” on the chalkboard he might see a red design in his mind and it would pop out at him. This is known as synesthesia. Ramachandran and Hubbard (2001) in their review of the subject proposed that these connections were due to to polymodal cross wiring, such that when hearing or seeing a word other modalities would also be stimulated so that he would experience the sight, taste, and feel of a spoken word instead of just the sound of it. This explanation they say is comparable to the experiences of phantom limb. But I think more must be going on for patient S. than just these cross-wirings. For just because he has such rich imagery ability, it doesn’t follow that he would be able to completely remember everything. In addition to his brain associating everything as visual cues he would also have to have photographic memory to be able to recall these lists. So my question is what else is going on? Could it be related to the NMDA receptors? Or does this patient just have more connections than the normal person?
Name:  Elizabeth Olson
Subject:  intelligence shmintelligence
Date:  2002-02-27 00:52:59
Message Id:  1242
The biggest problem I have with the concept of "intelligence" is that I feel that I have not yet encountered enough evidence to convince me that "intelligence," as a generalized phenomenon, exists. In fact, I think there are two reasons for which I doubt that intelligence as a generalized ability does exist: one theoretical, and one experiential. The theoretical reason that I am distrustful of the idea of generalized intelligence is that this concept does not make a whole lot of sense to me from the standpoint of evolutionary psychology. Evolutionary psychologists (exemplified by our old friends Toobey and Cosmides) contend that the brain consists of a large number of highly specific problem-solving mechanisms. Each evolutionary problem poses specific demands which are solved by specific mechanisms; the genes encoding for the most effective mechanisms are the genes that are most likely to be passed on. It seems to be that the concept of generalized intelligence confounds a number of evolutionary problems that as far as I can see have no logical reason to be related. For example, why would the mechanism that handles number processing (e.g. Meck and Church's accumulator mechanism) be confounded with areas that handle verbal processing (e.g. Broca and Wernicke's areas), etc.? It seems to me that these systems developed to handle very different types of problems and that they therefore probably have some degree of genetic distinction from each other.
The experiential argument I have against the concept of generalized intelligence relates back to a point I made during the discussion on Williams Syndrome in class the other week. I see Williams Syndrome as the extreme end of a spectrum that I think occurs in some so-called 'normal' individuals: On one end there are people who are extremely good at verbal skills, music, and social interaction, while at the other there are people who are extremely good at spatial skills, mathematics, etc. Of course, there are obviously people who are good at everything (good ol' Doogie Howser syndrome) and people who are bad at everything. I simply would need to see a lot more correlational evidence to be convinced that all of these aspects of intelligence can be bunched together into one unified whole. (To give a personal example, one of the researchers lumped motor reaction time in with other cognitive traits that constitute intelligence. If this is the case, man, am I in trouble. If my motor reaction time is supposed to serve as a good predictor of my verbal and math skills... well, suffice it to say, I would never have made it to Haverford, as anyone who has had the misfortune of seeing me attempt to kick a ball can attest).
Which takes us to the question of the 'smart,' NMDA-altered mice... It seems fairly obvious to me that there ought to be a number of manipulations that will speed up/ improve cognitive processing as a whole, and a number of manipulations that will slow it down as a whole (the 'smart' mice falling into the first category). I do not see this as compelling evidence that intelligence consists of one unified trait, however. I think there is too much compelling evidence to the contrary (see above). I think the functioning of the autonomic nervous system might serve as a useful analogy... If you give a person something that speeds up the autonomic nervous system (e.g., well, speed), you will see an increase in their heart rate, respiration rate, perspiration rate, etc. etc. etc. This does not necessarily mean that the heart, lungs, and sweat glands are part of one unifiable and undifferentiable system. Similarly, increasing NMDA activity in mice increases cognitive speed, planning, object recognition, etc. But I am not convinced that this means that the systems that control motor activity, planning, and recognition are undifferentiable from each other, as those who advocate for a unified 'g' would seem to purport.
I seem to have strayed somewhat far from the original questions... I am not convinced that a genetic explanation of intelligence is useful or desirable, mostly since I am not convinced that the traits that are currently lumped into the category of 'intelligence' are one unified force. Based on current observations, there seems to be a genetic influence on 'intelligence,' if you want to believe in the concept of generalized 'intelligence,' which I'm not sure that I do.
Name:  Mary Schlimme
Username:  Anonymous
Subject:  Intelligence and genetics
Date:  2002-02-27 01:55:06
Message Id:  1245
I think that intelligence is a useful concept, depending on how one wants to use it. I agree with Caroline who said that studying intelligence is similar to studying consciousness – and I think that we have to actually define what we mean by intelligence rather than assuming we all are referring to the same concept. For me intelligence isn’t measured by some IQ test or score on a standardized test – I think that intelligence refers to how one performs in the world in general, not just in academic settings. However, because researchers are required to define the variables they are measuring, I can understand why so many studies have used measures on IQ tests as a measure of a person’s intelligence.

Exploration of the genetics of intelligence is useful because it can help us understand how to better educate our children (since the tests of intelligence seem to be measuring academic ability or even on a more basic level test taking ability) – if we understand what role genetics play then we can presumably also determine the role of the environment in the development of intelligence. However, I think that this exploration needs to proceed with caution, especially if certain genes are found to determine intelligence. This brings up the ethical issues that we discussed the first week of class about whether it is acceptable for people to screen for certain traits and to genetically determine their children. By exploring the genetics of intelligence, we open the door to numerous debates on this issue.

Based on the readings for this week, I think that the evidence indicates that there is a genetic influence on intelligence. The article on the Doogie Mice (cleverly named) was fascinating to me, and it seemed that the methods were carried out well. The whole idea that you can make a mouse learn/remember more by making its NMDA receptors contain more NR2B subunits was remarkable. In a way though it almost seems impossible that such a seemingly simple switch led to such a dramatic effect (but this has amazing implications for how we can improve learning/memory in humans). In contract to my feelings about this article, I did not agree with the Thompson et al. article. Although these researchers found some interesting results (that “brain structure was increasingly similar in subjects with increasing genetic affinity”) I don’t think that their conclusions were very valid. First, as I understood it, the researchers did not specify whether the twins in their study were reared by their biological parents or by adoptive ones, suggesting that they did not tease apart the effects of the environment in this equation. Furthermore, one cannot draw causal links from correlational data, and I felt that the authors were pushing their ideas a little too strongly in the causal direction.

One area in which I am uncertain about my answer is how to define intelligence more appropriately. While I think that it is important to consider intelligence as a concept, I do not think that we should judge people as intelligent or unintelligent based on their scores on IQ tests. However, I am not entirely sure at this point how I would scientifically define intelligence so that I could measure it reliably.

Name:  Julia
Subject:  week 3
Date:  2002-02-27 01:57:27
Message Id:  1246
Intelligence can be a useful concept, but probably often isn’t one because of its broadness. Everyone probably thinks of intelligence in a different way or has different interpretations of what intelligence defines about a person. Does intelligence have to do with how well one does on standardized tests? Does intelligence have to do with how well a person structures their time, raises their children or generally lives their life? Or maybe there are many different types of intelligences. For example, most people would have the vocabulary to describe someone as book smart or street smart. Is intelligence part of both of these characteristics? Calling someone book smart implies that they are studious and educated. Calling someone street smart implies that they are sensible and quick thinking. Both types of intelligence require fast learning and good memory but information is taken in from the environment and processed in different ways. Intelligence as book smarts is much more easily assessed with standardized tests than street smart type intelligence can be. As a result, book smart intelligence is more like how intelligence is measured and perceived. Assuming that intelligence really is made up of many components, standardized tests lack the specializing that would be involved in recording all types of intelligence, therefore, this score is most likely and incomplete measure.
Despite IQ tests inadequacies they still do provide some means to compare genotype to phenotype. The exploration of the genetics of intelligence is still something worth while to look into. Although it does bring up many ethical questions about manipulating intelligence, but at the same time may bring relief to those suffering with dementia. Figuring out exactly what role genetics play in intelligence is no easy task since there are so many other variables in the environment such as education and social status that may have tremendous influence on intelligence or simply on an IQ score. There does seem to be some sort of correlation between genetics and intelligence. Genetics map out the range of possible intelligences. Smarter mice can be made by simple genetic changes allowing for a longer effect of NMDA receptors, but the genes that make them mice constrain them to solving tasks that smart mice can do, not allowing them to speak or problem solve like any human can do. The relationship between the environment and genetics is complicated and will probably never be fully understood. Simple genetics can have an impact on intelligence, as long as people keep in mind that there are other factors involved, genetic exploration may be a good start to uncovering the mysteries behind intelligence.
Name:  Caitlin Costello
Date:  2002-02-27 04:31:40
Message Id:  1248
Putting aside reservations about how heritability estimates are derived, etc., I was fairly convinced after reading the Carey chapters that g is, in fact, a useful concept and that generalized intelligence has a large genetic component. If, indeed, cognitive skills in all areas are highly correlated with one another (Carey did not go into detail or give much data on this rather hard to believe phenomenon), that would seem to legitimize g as an actual "thing", meaning that intelligence isn't as subjective as many people say. Now what does it mean that generalized intelligence has a large genetic component? (As Carey kept pointing out, almost all behavioral characteristics are moderately heritable, so why do we need to be talking about this in the first place....?) Carey discussed how IQ is more heritable than social status and education, which seem to be inherited by way of IQ. I wonder, though, whether IQ is the most directly heritable thing and should be the subject of focus. To score well on an IQ test, you have to have learned some things--vocabulary, how to rotate shapes, etc. And it would seem that someone who reads a lot will have a larger vocabulary than someone who doesn't, and someone who plays a lot of Tetris will be better at mental rotations. So what if more directly heritable than IQ itself is an interest in reading or in playing Tetris? I guess if g is real then it would have to be an interest in both...maybe an interest in problem solving or a general academic curiosity...I'm just not sure we should give up on an intermediate step in the heritability of intelligence like we seem to have found in the heritability of social status.

And what of "multiple intelligences"? It's kind of a feel-good concept...everyone has intelligences, and is just as smart as everyone else, just in different areas...but does it make sense? The theory presumes that levels of each of the multiple intelligences are not strongly correlated with one another, which seems to contradict the idea of g. I kind of wonder if it was a theory established in order to take away the value judgment associated with g (that some people have more g than others, and more is better), which might be good, but if g is real, isn't really accurate. Which is not to say that talent, which is how I tend to think of factors like "musical intelligence" can't be just as important as g, just that if many of the intelligence"s" are strongly associated with one another we shouldn't ignore that.

I would also like to see more data on how g is associated with positive outcomes, other than high social status and income, which involve a lot of choice and are not necessarily all that positive. What about happiness and satisfaction? It seems to me, just anecdotally, that really high-g people are not the happiest people. Maybe there's a maximum, moderately high level of g that is associated with greatest happiness and satisfaction; but maybe it is noncognitive intelligence--practical intelligence and social intelligence--that is more important to happiness (which seems to be the ultimate measure of positive outcomes). If that is the case, why are we spending all this time on g?

Name:  jess
Subject:  Intelligence
Date:  2002-02-27 13:59:02
Message Id:  1257
Intelligence is a complex topic that means something different to everyone. It is unfortunate that the majority of people use the word intelligence interchangeably with IQ for they are two very different constructs. Intelligence is what you make of it- from Spearman's g to the seven main intelligences to Galton's tests of cognitive abilities to the army alpha- intelligence is defined differently depending on the goal of the desired expertise. While some may find musical ability to be a kind of intelligence, others my see street smarts, common sense, or the ability to fix a computer as other kinds of intelligence. Certainly we all know someone who is incredibly book smart but gullible to the extreme so much that they are conned into the numerous schemes of others. What about the ability to succeed in life, those who are the most successful are often deemed intelligent, but for many different reasons, possibly they just got lucky. Is there any way to gage how successful a child will be in later life? So far, we have no diagnostic test for this- and maybe we never will, the closest we have come so far to quantifying this is EQ. Therefore, thus far intelligence is a loosely defined construct that is unable to be measured.

IQ however contains great construct validity and is reliable on almost all measures. It tests certain cognitive abilities that have been defined by test creators as measuring intelligence as related to expected school performance. This is not to say that poor standardized test takers cannot do well in school, just that it is an indicator of school performance. IQ test have been designed so that a score given at one point in life remains relatively constant over time. This is counterintuitive to what many believe which is that humans gain wisdom as they age. However IQ tests do measure what they say they measure and if a person does well on one type of test of cognitive ability they tend to do equally well on others.

When it comes to genetics, heritablity does play a large role, but it is surprising how little a role environment plays. I found it quite surprising that adopted children don?t resemble their adoptive parents on measures of verbal and spatial ability but birth mothers and these adopted children are just as similar as control children living with their birth parents, as of middle childhood. I would have hoped environment had had more effect. I find this especially worrisome because this might lead parents to downplay the effect of environment to the point where they place less of a role in educating their children.

Name:  Nirupama Kumar
Subject:  flowers for algernon?
Date:  2002-02-27 17:11:02
Message Id:  1263

"Intelligence" is at best a pretty ambiguous concept. There are of course IQ tests, standardized test scores, grades, and more subjective criteria like creativity. I suppose from a scientific/behavioral view a specific definition may be attributed to intelligence. Still the measure of it is always tricky. Because intelligence has such broad array of influences having one set definition runs into problems as well. From a cultural standpoint, different types of learning could be emphasized--making someone seem intelligent in one culture, but not intelligent in another. Ie, some cultures emphsize mathematical learning, while another highlights more linguistic aspects of learning. Even an IQ test, taken at face value may have little scientific value. The values are based on the relative scores of other people with 100 as the average. All of this makes any scientific evaluation of intelligence very muddled. We can measure how extra NMDA receptors make mice do better than their ordinary counterparts at certain tasks, but this demonstrates only one component of intelligence: memory. (I also just want to note the Flowers for Algernon feeling of that experiment...) It seems that it would be much more scientifically useful to use as specific of a term as possible when describing mental features. Intelligences implies too broad a spectrum of qualities to be useful in this way.

Given this relative uselessness of intelligence, I think that the exploration of genetic intelligence is going to be a fruitless search. One must acknowledge the multi-faceted nature of intelligence and recognize that there can be no direct genetic correlate to intelligence overall. I think that examing the many genetic factors which contribute to intelligence is much more helpful in our understanding of the mind and very desirable. By exploring the genetic components we can certainly learn more about the nervous system. There may be some perceived social impacts for the worse, but those should not even be considered here.

I think that the articles we read do point to individual components of intelligence which are genetic. I think that the twin studies conducted to measure intelligence are somewhat less useful and direct in their certainty of a correlation between intelligence and genetics because they didn't identify a specific component. I did find it interesting that they seemed to show how environment played a lesser role than genetics, but I still feel skeptical.

I am somewhat uncertain about my answers because I feel unsure about the definition of intelligence in general. I also am hesitant because I know that there are morphology differences which one can detect to compare the intelligence of two people. But, it is very hard to quantify these things into one objective standard. If such a standard where described to me I might change my stance. I think more genetic studies need to be done, not just statistical correlations between twins and adopted children.

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