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Pollitt (1995)

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  • Pollitt (1995)

For years psychologists have argued that poverty has an effect on a child’s cognitive development. The problem with this argument, of course, is that there are many aspects of poverty that may be the “cause” of cognitive impairment. One of the variables that has been studied by psychologists is malnutrition.

The following study may be used to discuss the role of "socioeconomic factors" on cognitive and/or social development.

Procedure and results

Pollitt carried out a study in four extremely poor villages in central Guatemala for a period of eight years. Because it was thought that protein was the most important nutrient missing from the villagers’ diet, it was decided to give villagers a nutritional supplement. Participants were pregnant women and children under the age of 7. More than 2000 children and mothers participated between 1969 and 1977.

Participants in two of the villages received a high protein supplement called Atole. The inhabitants of the other two villages - who served as the control group - received Fresco, which contained no protein. Both supplements provided vitamins and minerals as well as calories, but Fresco only had one-third of the calories of Atole.

The findings showed a significant drop in infant mortality in both sets of villages, but with a 69% decrease in villages taking Atole and only a 24% decrease in the villages taking Fresco. Children on Fresco suffered a slower rate of growth and a slower rate of recovery from infection. They also learned to crawl and walk slightly later on average. Because these undernourished children remained small for their age, adults may have treated them as if they were younger than their actual age.

The follow-up study was carried out in 1988, eleven years after the completion of the first study. The participants who received Atole in early life performed significantly better on most tests of cognition compared to those who received Fresco. Children from the lowest socio-economic level of the village scored just as high as those in the higher SES of the village. With every additional year of schooling, the differences in achievement between those children who took Atole vs. Fresco increased. However, the children from the villages still performed less well than children from a middle-income household in a more prosperous area of Guatemala.

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Checking for understanding

1. What type of study is this? Describe the design.

The study is an experiment that uses an independent samples design.

2. What is meant by the statement that the inhabitants of the other two villages "served as the control group?"

It means that they did not get the treatment. In this case, it is a little confusing because they do get a treatment of sorts; they receive a dietary supplement as well. There are several reasons why the researchers may have given this supplement to the other village. Most probably, it was to avoid the placebo effect.  In addition, it could be to make sure that the other villages had a minimum daily intake of vitamins, minerals and calories. The researchers were interested in the effect of protein on cognitive development. This helps to lower, but not eliminate, the confounding variable of other deficits in the children's diet. It could have also been an ethical consideration. By giving a supplement to both groups, it lessens the ethical concerns. Finally, it could have been a way of building up trust with the other villages. By giving them the supplement, they would have probably been more willing to be studied and to give their data for research.

3. Discuss the findings of the study. To what extent can we conclude that malnutrition has an effect on cognitive development?

It appears that protein plays a significant role in cognitive development. However, it also seems that other factors seem to also play a key role in the differences in cognitive development that are seen in different SES groups. Clearly, protein is only one factor.

4. To what extent could we generalize the results of this study?

Generalization of the findings could be improved if we have other examples of similar research which reached similar conclusions. We can also talk about the "transferability" of the findings - that is, it could be generalized to other Guatemalan villages, but perhaps not to other developing countries. There may be predispositions within a given community or there could be other dietary considerations in other communities.

5. Discuss ethical considerations with regard to this study.

It is not an ethical concern that two of the villages did not get the protein supplement. The researcher did not cause harm to the other villages as the participants' health was not decreased. It is simply that they did not get the advantage of the protein supplement. In fact, the researcher ended up helping the community by giving them Fresco. The ethical concerns for this study include the confidentiality of the cognitive data as well as the question of what happened at the end of the study. Were the supplements simply discontinued at the end of the study? This is most likely the case. However, one of the goals of psychology is to improve people's lives. So, being able to apply the research and encourage governments to provide supplements for the poor (e.g. free breakfasts at poor urban schools in the US or in rural Guatemala) could be a positive outcome of this study.