Is the size of your brain an indicator of your mental capacity? Are human brain

Question

Is the size of your brain an indicator of your mental capacity? Are human brain size and intelligence related to each other? The relationship between brain size and intelligence has been a topic of a scientific debate since at least 1830s. The first researchers in this area often used external skull measurements or waited until a person died to estimate brain size. The most recent advances in technology, in particular Magnetic Resonance Imaging (MRI) allowed to create very accurate brain size measurements. In 1991, Willerman et al. used the technology to examine the relationship between brain size and intelligence for a random sample of university students. Brain size of the subjects selected for the study was determined by MRI scans and intelligence was measured with several standardized intelligence tests. For detailed information about the study, refer to the paper by Willerman, L., Schultz, R., Rutledge, J. N., and Bigler, E. "In Vivo Brain Size and Intelligence", Intelligence, 1991, 15, 223-228. For your convenience, we summarize below all the most essential information required to answer the lab assignment questions.

The study was conducted at a large southwestern university in the U.S. Researchers randomly selected a sample of 40 students from a larger pool of right-handed Anglo introductory psychology students, who had indicated no history of alcoholism, unconsciousness, brain damage, epilepsy, or heart disease and had volunteered to participate in the study. MRI was used to determine the brain size of the subjects. The MRI scans were performed at the same facility for all 40 subjects. Each person had 18 horizontal MRI scans of their brains taken. The computer counted all pixels with non-zero gray scale (indicating the presence of gray matter) in each of the 18 scans and the total count served as an index for brain size. Information about gender and body weight is also included. All 40 students studied took an IQ test.

What is the purpose of the study? What is the response variable? What are the explanatory variables? Can you explain why body weight was included among the explanatory variables?

Column Variable Name Description of Variable GENDER PIQ 0-Female, 1=Male; Performance IQ scores based on the four Wechsler (1981) subtests (Vocabulary, Similarities, Block Design, and Picture Completion) Total pixel count from the 18 MRI scans, Body weight in pounds. MRI WEIGHT 4

Explanation / Answer

Purpose:

To find if brain size has an effect on intelligence of a person.

Response Variable :

PIQ

Explanatory variables:

GENDER, MRI, WEIGHT.

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