Hi

Looks like the specific results for caudate are even weaker than Chris has 
suggested. Here’s the closing paragraph.

This study provides the first report of a positive associa-
tion between bilateral caudate volume and IQ, in three
large, independent, nonclinical adult samples. Constraining
the effect of caudate volume to be equal across all three sam-
ples produced a well-fitting model and suggested that cau-
date volume accounts for somewhere between 2.4% and
4.3% of variance in IQ. Due to the fact that the present analy-
ses are purely correlational, determining the specific mecha-
nisms that account for the association between intelligence
and caudate volume is an important goal of future research.

And of course there is that closing line, acknowledging the gap between 
correlation and mechanism.

Take care
Jim

Jim Clark
Professor & Chair of Psychology
University of Winnipeg
204-786-9757
Room 4L41 (4th Floor Lockhart)
www.uwinnipeg.ca/~clark<http://www.uwinnipeg.ca/~clark>

From: Christopher Green [mailto:[email protected]]
Sent: Sunday, January 03, 2016 10:15 AM
To: Teaching in the Psychological Sciences (TIPS)
Subject: [tips] Subcortical intelligence: caudate volume predicts IQ in healthy 
adults. - PubMed - NCBI



This article has been getting a lot media play over the past couple of days 
(which is interesting in itself, since it was published back in April). It 
strikes me, however, as a classic example of paying way too much attention to 
p-values and not enough to effect sizes. Yes, the effects are significant 
(mostly), but if you look at the full article, it appears that the R-squares 
range from  .11 downwards. Not exactly a Eureka! moment.

http://www.ncbi.nlm.nih.gov/pubmed/25491047?utm_content=buffer077fa&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Chris
.......
Christopher D Green
Department of Psychology
York University
Toronto, ON   M3J 1P3
43.773759, -79.503722

[email protected]<mailto:[email protected]>
http://www.yorku.ca/christo

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