Among the section of the right that regards IQ as the only explanatory variable in society aside from money, the relationship between poverty and IQ is used to defend the huge inequities in ours society as an outcome of a functioning meritocracy. It does not require much deep inspection of how modern capitalist societies work to see that they are neither functioning well not are they meritocracies.
The opposite view is that difference in performance on IQ is more caused by poverty than vice-versa. There are multiple reasons for believing this from access to education, motivation and attitudes towards the role of test taking in a person’s life (e.g. how much effort do you put into something that you expect to do poorly in?) However, specific causes are hard to demonstrate empirically. Hard to demonstrate, perhaps, but maybe a clever experimental design can shed more light on that.
I was just reading a 2013 paper that looked at the impact of poverty on cognition in an interesting way: Poverty Impedes Cognitive Function Anandi Mani, Sendhil Mullainathan, Eldar Shafir, Jiaying Zhao (Abstract http://science.sciencemag.org/content/341/6149/976 )
“The poor often behave in less capable ways, which can further perpetuate poverty. We hypothesize that poverty directly impedes cognitive function and present two studies that test this hypothesis. First, we experimentally induced thoughts about finances and found that this reduces cognitive performance among poor but not in well-off participants. Second, we examined the cognitive function of farmers over the planting cycle. We found that the same farmer shows diminished cognitive performance before harvest, when poor, as compared with after harvest, when rich. This cannot be explained by differences in time available, nutrition, or work effort. Nor can it be explained with stress: Although farmers do show more stress before harvest, that does not account for diminished cognitive performance. Instead, it appears that poverty itself reduces cognitive capacity. We suggest that this is because poverty-related concerns consume mental resources, leaving less for other tasks. These data provide a previously unexamined perspective and help explain a spectrum of behaviors among the poor. We discuss some implications for poverty policy.”Poverty Impedes Cognitive Function Anandi Mani et al. Science 341, 976 (2013); DOI: 10.1126/science.1238041
First some caveats. It’s two fairly narrow experiments both of which have some contrived circumstances (for good reasons). I don’t know if these results have been reproduced.
Having said that it is interesting to look at the two experiments and what the results were.
The basic hypothesis was this:
“We propose a different kind of explanation, which focuses on the mental processes required by poverty. The poor must manage sporadic in- come, juggle expenses, and make difficult trade- offs. Even when not actually making a financial decision, these preoccupations can be present and distracting. The human cognitive system has lim- ited capacity (12–15). Preoccupations with pressing budgetary concerns leave fewer cognitive resources available to guide choice and action.Poverty Impedes Cognitive Function Anandi Mani et al. Science 341, 976 (2013); DOI: 10.1126/science.1238041
To test this they compared individual performance on cognitive test both with and without some degree of financial stress. The first was a ‘laboratory study’ that demonstrates the impact as a kind of proof of concept. The financial stress here is artificial but if anything that makes the results more interesting.
In the first study the researchers went to a New Jersey shopping mall and recruited shoppers (who got paid) to take part in four related experiments. The basic principle of each experiment was two tasks. One task asked people to consider a realistic but hypothetical financial problem. For example, they might be asked about their car having to get some urgent repairs. Participants randomly were given a ‘hard’ situation were the costs would be high or an ‘easy’ situation were the costs were low but both easy & hard situations were cognitively similar. The second task was a more classic IQ style test (Raven’s Progressive Matrices) and a spatial compatibility task.
The four versions were designed to control for cognitive impacts of the first activity. The first two versions changed the amount of maths needed in the financial scenario. The third version added incentives to correct answers. The fourth version separated the two activities so that the first was completely finished before the person sat the IQ style test.
The group being studied also provided information on their income and the the data was analysed by looking at the participants as either rich or poor. The point being to see not if the ‘rich’ participants performed better on the IQ test but rather how much impact did the first activity (i.e. having to engage with a potentially financial stressful situation) have on the cognitive scores
The graph is for experiment 1 but the results were similar for all four. The impact of ‘hard’ versus ‘easy’ of the first activity on the second activity was much bigger for people with less money. For the wealthier participants, the ‘hard’ scenario had less impact, almost certainly because they were faced with a situation that would have less of an impact on their own finances. In short having to worry about money and how you will pay for things that you need has a genuine and measurable impact on your ability to perform some cognitive tasks… At least within this experimental scenario but that a PRETEND bit of financial stress had a measurable impact is itself notable.
The second study was quite different and looked at some real financial stress.
“Our second study examined 464 sugarcane farmers living in 54 villages in the sugarcane- growing areas around the districts of Villupuram and Tiruvannamalai in Tamil Nadu, India. These were a random sample of small farmers (with land plots of between 1.5 and 3 acres) who earned at least 60% of their income from sugarcane and were interviewed twice—before and after harvest—over a 4-month period in 2010. There were occasional nonresponses, but all of our pre- post comparisons include only farmers we surveyed twice. “Poverty Impedes Cognitive Function Anandi Mani et al. Science 341, 976 (2013); DOI: 10.1126/science.1238041
The work of the sugarcane farmers created a set of natural controls. An individual farmer has only one harvest a year and hence essentially only one pay-day a year. However, the timing of harvests are staggered over several months. So at a particular time of year it maybe post-harvest for one farmer but pre-harvest for another. The farmers naturally face greater financial pressure the longer it has been since their last harvest.
The results showed a similar but slightly smaller impact than the laboratory study. Farmers performed better on an IQ style test (Raven’s Progressive Matrices) after* they had been paid than before and the difference was large.
How large are these effects? Sleep researchers have examined the cognitive impact (on Raven’s) of losing a full night of sleep through experi- mental manipulations (38). In standard deviation terms, the laboratory study findings are of the same size, and the field findings are three quarters that size. Put simply, evoking financial concerns has a cognitive impact comparable with losing a full night of sleep. In addition, similar effect sizes have been observed in the performance on Raven’s matrices of chronic alcoholics versus normal adults (39) and of 60- versus 45-year-olds (40). By way of calibration, according to a common approximation used by intelligence researchers, with a mean of 100 and a standard deviation of 15 the effects we observed correspond to ~13 IQ points. These sizable magnitudes suggest the cognitive impact of poverty could have large real consequences.Poverty Impedes Cognitive Function Anandi Mani et al. Science 341, 976 (2013); DOI: 10.1126/science.1238041
Put another way: we don’t think in isolation (even if you aren’t neurotypical). Background concerns and worries all have an impact on how you think and your capacity to problem solve. They definitely have an impact on your thinking in the artificial conditions of an IQ test.
*[There were also controls on the order they did the tests. Some of the participants took the test first after they had been paid and then were tested later in the year when their money had run low.]