Question is whether they controlled for low end outliers. If the smaller caudate sample included cases where the caudate was abnormally small because of some pathology, this would make the result artifactual.
On Jan 3, 2016, at 10:27 AM, Jim Clark <[email protected]> wrote: > > 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 > > 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 Paul Brandon Emeritus Professor of Psychology Minnesota State University, Mankato [email protected] --- You are currently subscribed to tips as: [email protected]. To unsubscribe click here: http://fsulist.frostburg.edu/u?id=13090.68da6e6e5325aa33287ff385b70df5d5&n=T&l=tips&o=47732 or send a blank email to leave-47732-13090.68da6e6e5325aa33287ff385b70df...@fsulist.frostburg.edu
