Given the results of this study, why can’t the researchers draw a causal connection

between type of food and later intelligence? What might be an alternative

explanation for the results of this study? What could the researchers

do in order to make a causal connection between the dependent and independent

variables?

Chapter 1 LAB
Critical Thinking Activity: Breast-Feeding and Intelligence
Now that you have read and reviewed Chapter 1, take your learning a step further
by testing your critical thinking skills on this scientific reasoning exercise.
Several studies suggest that breast-fed babies become more intelligent children
than formula-fed babies. One such study (Mortensen, Michaelsen, Sanders,
& Reinisch, 2002*) involved a sample of over 3,000 women and men born in
Copenhagen, Denmark, between October 1959 and December 1961. The samples
were divided into five categories based on duration of breast-feeding, as assessed
by physician interview with mothers at a one-year examination. The child’s intelligence
was assessed using the Wechsler Adult Intelligence Scale (WAIS) at a
mean age of 27.2 years.
The results showed that duration of breast-feeding was associated with significantly
higher scores on the verbal, performance, and full scale WAIS IAs. This
difference was observed even after the researchers adjusted for differences in the
social class and maternal education of the two groups. (This adjustment allowed
the researchers to rule out any preexisting differences in the groups that might
have independently contributed to IQ differences in their children.)
The authors acknowledged that other differences between the groups, such
as the children’s genetic potential or their parents’ caregiving skills or motivation
to nurture, could explain the results. However, they believe that human milk
contains various hormones and other factors that enhance brain growth and
maturation. 1. State the research hypothesis in your own words. Identify the independent
and dependent variables, and define all important concepts and terms as they
are used in this study. 2. What evidence do the researchers offer as a test of their hypothesis? Is this
evidence empirical (observable)? Is it valid? 3. What explanation do the researchers offer for their findings? Does this explanation
make sense based on the evidence? 4. Given the results of this study, why can’t the researchers draw a causal connection
between type of food and later intelligence? What might be an alternative
explanation for the results of this study? What could the researchers
do in order to make a causal connection between the dependent and independent
variables? 5. Are there any practical implications for this research? *Mortensen, E. L., Michaelsen, K. F., Sanders, S. A., & Reinish, J. M. (2002).
The relationship between duration of breastfeeding and adult intelligence.
Journal of the American Medical Association, 287, 2365–2371.

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