Intelligence: is your social class important when it comes to inequalities in health, and how?

Written by Nea Lulik, MSc in Psychology of Individual Differences

Virtually all indicators of health favour people of higher socio-economic status (SES). SES and health outcomes are generally consistent with time, place, disease, and health-care system and are finely graded up the SES continuum. This article argues that general intelligence (g) is the fundamental cause for health inequality.

g is a highly general ability and it plays a big role in performing a job well and getting ahead, socio-economically. g can influence individuals’ behaviour, as well as society’s social, political and economic outcomes. Because of these generalizations in various areas, g can be assessed as a predictor to explain these outcomes. The author refers to this network of generalizations and related predictions as g theory.

The main questions are:

Do the data of daily self-maintenance, health self-care, prevention of accidental injury conform to the predictions of g theory? Does g theory explain the social class differences in health better than can conventional theories of social inequality?

Conventional theories of social inequality presuppose that social class disparities in health are due to the material resources, such as access to medical care. But in the countries that made improvements in the health system and made it equal for everyone, the results show, that greater equalization of health care results in even wider social class disparities.

The argument is that g is the fundamental cause because it meets six criteria that every candidate for the cause must meet: stable distribution over time, is replicable, is a transportable form of influence, has a general effect on health, is measurable, and is falsifiable. It has been proven that g meets all but the fourth criteria – g’s general effect on heath knowledge, behaviour and outcomes. 

Income, occupation, education, health literacy (efficient learning, reasoning, problem solving) are strong correlates of health outcomes.

g is content- and content-free ability to process information of any sort. The high generality of g is also seen in the more specific skills and abilities that specify a high-g person (reasoning, conceptual thinking, problem solving, and quick and efficient learning) – all these general-purpose abilities are applicable to any task or life setting. g predicts job performance to some extent (in an indirect way), especially when the job isn’t closely supervised and it does not follow a routine, and it requires lots of novel problem solving, planning and decision making. Experience and favourable trait can compensate to a certain extent for lower levels of g, but they can never negate the disadvantages of information processing that is slow or error prone.

National Adult Literacy Survey (NALS) measures performance on simulated daily tasks involving written material, which are essential for one to participate effectively in modern society. It resembles the test for general intelligence, and all the skills that are tested, are prototypical manifestations of g. Comparing the NALS test to IQ reveals the same pattern of effects.

Not all people learn equally well when exposed to the same instructions, because higher g promotes faster, more extensive and more complete learning of what is being taught. Also, information processing is involved in all daily tasks, so higher g always provides an edge. Therefore, inadequate thinking skills can result in health problems.

Age-specific rates of illness and death are often two/three times higher in the lower class strata. Greater access to medical care has surprisingly little relation to differences in health. Equalizing the availability of health care does not equalize its use. Less educated and lower income individuals seek preventive health care less often than better educated or higher income people, even when care is free. Health depends more on private precaution and healthy lifestyle (healthy choices about our own behaviour), than on medical care. 

Rates of illness and death are progressively lower at higher social ranking. Graded relation between class and health is found regardless of whether social class is measured by level of education, occupation, or income.

The six criteria (that g is the fundamental):

· Stability: Equalizing socio-economic environments does little to nothing to reduce the dispersion in IQ (Frikowska et al., 1978, in Gottfredson, 2004). The dispersion of IQ in a society in general is more stable, than its dispersion of socio-economic advantage (Plomin et al., 2001, in Gottfredson, 2004).

· Replicability: Siblings who differ in IQ also differ in socio-economic success to about the same degree as do strangers of comparable IQ (Jencks, et al., 1979; Murray, 1997, 1998, in Gottfredson, 2004). Also, g theory predicts that if genetic g is the principal mechanism transmitting socioeconomic inequality from one generation to the next, then the maximum correlation between parent and child SES will be close to their genetic correlation for IQ, which is about .50. Intergenerational SES correlations have remained stable despite improvements in social conditions.

· Transportability: The performance and functional literacy (NALS studies) studies both illustrate how g represents a set of highly generalised reasoning and problem-solving skills. g seems to be linearly related to performance in school, jobs and achievements.

· Generality: Studies show that IQ measured at the age of 11 predicted longevity, cancers, dementia, and functional independence more than 60 years later (Deary et al., 2004, in Gottfredson, 2004).

· Measurability: g factor can be extracted from any broad set of mental tests and has provided a common, reliable ground for measuring general intelligence in any population. Among the usual indicators of class, years of education is the most g loaded because it correlates .68 with IQ, whereas occupation and income correlate .50 and .35 with IQ (Jencks et al., 1972, in Gottfredson, 2004).

· Falsifiability: g theory would conceive health self-care as a job, a set of instrumental tasks performed by the individuals, so it would predict g to influence health performance in the same way as it predicts performance in education and work.

Now, chronic illnesses are the major illnesses in developed countries today, and their major risk factors are health habits and lifestyle. The higher social strata knows the most and the lower social strata knows the least, whether class is assessed by education, occupation or income and even when the information seems to be most useful for the poorest. Education was the best predictor in this case again. Higher g promotes more learning, it increases exposure to learning opportunities and then allows for their fuller exploitation. 

Health literacy predicts health knowledge, health behaviour and health

The problem is not in the lack of access to care, but the patient’s failure to use it effectively when delivered. Some patients are unable to understand even the simple information about their disease. Low literacy has been associated with low use of preventive care, poor comprehension of one’s illness, and delay in seeking screening for cancer – even when care is free.

Health literacy reflects mostly g – TOFHLA test – similar to NALS except is for health

TOFHLA literacy is similar to functional literacy and work literacy (mostly g). Low literacy remains a significant disadvantage even when people receive instructions in what they are motivated to learn. These results are consistent with the job performance research, as in training and experience help, but do not neutralize the disadvantage of low g. 

Health self-management is important because literacy provides the ability to acquire new information and complete complex tasks and that limited problem solving abilities make low-literacy patients less likely to change their behaviour on the basis of new information. Chronic lack of good judgement and effective reasoning leads to chronically poor self-management. With the technology, the self-care is becoming more complex, and therefore high g people will benefit more than lower g patients.

Accidental injury and death: Some people tend to have more accidents than others even with the same level of exposure to the same hazards in the same environment. The risk of accidents is higher in workers with fewer years of experiences and less knowledge, and when the tasks are more complex, novel or confusing. Errors increase when tasks demand higher cognitive abilities. 

People in lower class neighbourhood are more prone to higher risks of accidents but not intended deaths. Higher mortality in higher class is only present in one category – aircraft accidents. Risk of death by lightening is also more common in lower class neighbourhood. People in the poorer neighbourhood are also more likely to be murdered than those in middle class area. The risk of death by fire is also more common in poorer than richer neighbourhood, especially for children and elderly.

There is something about life in lower social class that increases vulnerability in general.

The more personal choices we have in conducting our life as we see fit, the more our fate depends on our own knowledge, judgement and foresight – hence, g. All accidents are amenable to some control, and same as with jobs, the higher the g the better the outcome. Technological and social advance greatly increase both the complexity of our life and the choices we have. Although we welcome more choice, both choice and complexity put a big premium on g. 

Reference: 

Gottfredson, L. S. (2004). Intelligence: Is it the Epidemiologists' Elusive "Fundamental Cause" of Social Class Inequalities in Health? Journal of Personality and Social Psychology, 174-199.