A challenge for psychologists researching the influence of poverty on development is that poverty comprises so many independent and interacting variables: such as stress, malnutrition, lack of adequate housing or adequate schooling. Any and all of these can have an effect on childhood development, and so it is difficult to isolate any one of them. This essay will evaluate the research used by psychologists to investigate the influence of poverty on children’s cognitive and social development.  

Introduction and focus on the question: a brief mapping of the planned essay and explains the issue - why the evaluation of empirical evidence is important in psychology.

In one of the earliest studies to link malnutrition and cognitive development, Pollitt et al. conducted a longitudinal case study between 1969 and 1977, with a quasi-experimental design, in order to investigate the role of nutritional supplements in improving cognitive development.  The 2000+ participants lived in four poor villages in Guatemala. Inhabitants of two villages received a high-protein mineral and vitamin supplement called Atole, while those in the other two villages received a supplement (Fresco) which contained minerals and vitamins, but no protein and fewer calories. Data was gathered on pregnant women and children under the age of 7, who comprised the target population of this research.

Knowledge and understanding shown of research into the influence of poverty on social and cognitive development.

At the end of the research, infant mortality was found to have dropped by 69% amongst those who took Atole and by 24% in those who took Fresco. Children on Fresco showed lower achievement on cognitive tests compared to children on Atole. A follow-up study 11 years later showed the same developmental gap between those who had Atole in early childhood and those who had Fresco, showing the long-lasting benefits of protein supplements pre-birth and in early life.

However, there are some limitations to the study. Given the cultural differences in the diet of people in poverty, we cannot be sure that these findings are generalisable to all communities, though they may well apply to other Guatemalans in poverty.  Moreover, all of the children showed delayed development compared to middle-class children in a richer area of Guatemala, suggesting environmental influences that are separate from diet alone. Pollitt et al. point out that the housing, sanitation and schooling were all severely sub-standard and this is bound to have an additional effect. As the supplements improved the diet of all the mothers and children, the research can be seen as ethical, though once the superior benefits of Atole became clear, it should have been offered to all, rather than (as probably happened at the end of the research) being withdrawn once the study was completed.

The internal validity of the study is high, as there were no significant differences between the villagers at the beginning of the study, and all variables apart from the supplements remained the same, so a positive correlation between nutritional supplements in early childhood and improved cognition was demonstrated. Moreover, the difference between the two groups was maintained 11 years later, even when the children no longer took the supplements.  This is enough to develop a testable theory that can be used in research outside of this narrow demographic.

Use of research to support answer: further evaluation of Pollitt et al. showing the strengths.

Noble et al. (2005) moved away from the effects of malnutrition alone to look at the correlation between lower socio-economic status (SES) and cognitive functioning. SES is a measure of a person’s position in life, based on income, education and occupation, so it is a broader measure than mere poverty. This was a quasi-experimental design, using 30 middle-SES and 30 low-SES urban African-American children from a Philadelphia kindergarten. The children were given a battery of standardised cognitive tests and researchers identified a correlation between SES and individual differences in language ability and executive functions such as working memory and self-control, with the low-SES children scoring significantly less than the middle-SES children on tests of language and executive function.  Because language and behaviour like self-control are social as well as cognitive, this is a particularly important discovery, as it shows the overlap between cognitive and social development.

Clarity and organization throughout; each paragraph makes a logical connection with the one before it.

Use of research to support answer: description of Noble et al.’s research.

Knowledge and understanding of the research method shown.

One strength of Noble et al.’s study is its internal validity.  SES was operationalised by parental education, occupation and income-to-needs ratio. Although this makes those factors hard to separate, it gives the construct high validity.  The cognitive testing was conducted using many standardised tests that had been developed to measure the particular neurocognitive functions, and so the correlation found should be valid. However, the extensive testing under artificial conditions would reduce the ecological validity of the findings.  For example, it may be that children from a low-SES would show more varied vocabulary use under non-test conditions.  Another limitation of the study is the small sample size. The study would need to be replicated outside of this narrow urban African-American population to ensure the reliability of the results. Moreover, if this had been a longitudinal study, the researchers could have assessed the long-term validity of their findings.

Use of research to support answer: strengths and limitations of the study.

In a natural experiment, Mani et al. (2013) investigated cognitive load as influenced by poverty. This was part of a series of experiments conducted by the researchers, in which they found that the poor did worse on cognitive tests because the reasoning they needed to use gave a cognitive overload when they had financial worries. Having gained this result in lab experiments, Mani et al. tested their hypothesis with 464 sugar cane farmers in India whose main source of income was from their cane. Before the harvest, they were at their poorest and performed quite badly on an IQ test and the Stroop test.  However, after the harvest, they were at their richest and performed significantly better.  Mani et al. argue that this is because poverty had an effect on the farmers’ ability to manage the cognitive load associated with the tasks. They conclude that poverty itself overloads cognitive functioning and this incapacity can, in turn, lead to more poverty.

Use of research to support answer: description of Mani et al.’s research

The fact that this is a natural experiment gives it ecological validity in that the farmers are in their usual habitat.  However, the cognitive tasks themselves, an IQ test and the Stroop test are irrelevant to the farmers’ daily lives, and so it may have been lack of motivation when worried, rather than cognitive load, that gave the low pre-harvest results. The main problem is Mani et al.’s generalization of the findings as demonstrating an incapacity for reasoning amongst the poor that contributes to their poverty.  The study merely showed a reduced capacity on irrelevant tasks and it may be that their financial management is unimpaired during the pre-harvest period. Replication is needed using more relevant cognitive tasks, such as budgeting and management of resources, in order to confirm the role of cognitive load in the perpetuation of poverty.

Use of research to support answer: evaluation of Mani et al.’s research – limitations and strengths identified and explained.

To conclude, these three different studies each contributed significantly to the body of knowledge regarding the impact of poverty on cognitive and social development. It is now generally accepted that a deficient diet, low-SES and stress are all risks associated with poverty that contribute to delayed cognitive, and in some cases social, development.