“That’s the difference in IQ between a person who is a normal adult versus a chronic alcoholic,” Mani said. “In terms of age, it’s like an average 45-year-old as opposed to an average 60-year-old. In terms of sleep loss, [the immediate impact of the mall study] is like losing a full night of sleep.”
For the Indian farmers, there was a similar but smaller effect.
“What we did is look at the same people the month before and the month after the harvest, and what we see is that IQ goes up, cognitive control, or errors, goes way down, and response times go way down,” professor of economics at Harvard University and co-author of the study Sendhil Mullainathan said. “The effect here is about two-thirds of the size of the effect found in the mall study — it’s at least nine or 10 IQ points, just between these months.”
In their study, the researchers controlled for possible mitigating factors such as stress, quality of nutrition, available time and also the fact that people can sometimes get better at cognitive tests once they have tried them out a few times.
Mullainathan added that “the results are not suggesting that the poor as people have less cognitive capacity, but that anyone experiencing poverty would have less capacity. I realize this is basic, but it is such an easy mistake to make in interpreting the conclusion.”
Joanna Wild, a clinical psychologist at the University of Oxford, who was not involved in the study, said the latest results were novel because, previously, researchers “may have thought that environmental conditions, such as lower levels of education, explained the link between poverty and poorer performance on some tasks of intelligence compared to the rich.”
She added that a limitation of the study was that the researchers had not studied how the financial questions in the shopping mall scenario had affected the emotional states of the participants. The US$1,500 amount in the “hard” scenario may have failed to influence the cognitive processing of participants with higher incomes because it might have been too low to be meaningful to them, she said.
“The figure of US$1,500 may have led to anxiety in low income participants, which could have influenced their performance. The study failed to look at affective state. How much anxiety did the imagined scenarios create and were their differences in how anxious high and low income participants felt, which could explain there differences in performance?” she said.
Mani said that the results of the study had implications for policymakers.
“When we think of poor people and design policies and programs to help them, we are only particularly cognizant of the fact that they have less material resources,” she said. “I think that programs don’t often appreciate that they’re also, precisely because of poverty, a bit challenged in terms of the mental resources and attention that they have. To the extent that we want to make anti-poverty programs effective, we want to design them in a way that is mindful of that.”
This could mean helping poorer high-school students fill in application forms for financial aid rather than leaving them to do it by themselves. Rather than assuming that many of the poor are not taking advantage of beneficial schemes through lack of motivation or interest, Mani said, help with “small nudges at the right time and limiting the amount of cognitive load that become barriers to them enrolling in the program could make a big difference.”