Jeff Lax pointed me to this online article by Jeanna Bryner:
Higher education tied to memory problems later, surprising study finds
Going to college is a no-brainer for those who can afford it, but higher education actually tends to speed up mental decline when it comes to fumbling for words later in life.
Participants in a new study, all more than 70 years old, were tested up to four times between 1993 and 2000 on their ability to recall 10 common words read aloud to them. Those with more education were found to have a steeper decline over the years in their ability to remember the list, according to a new study detailed in the current issue of the journal Research on Aging. . . .
As Jeff pointed out, they only consider the slope and not the intercept. Pehaps the college graduates knew more words at the start of the study?
Here’s a link to the study by Dawn Alley, Kristen Southers, and Eileen Crimmins. Looking at the article, we see “an older adult with 16 years of schooling or a college education scored about 0.4 to 0.8 points higher at baseline than a respondent with only 12 years of education.” Based on Figures 1 and 2 of the paper, it looks like higher-educated people know more words at all ages, hence the title of the news article seems misleading.
The figures represent summaries of the fitted models. I’d like to see graphs of the raw data (for individual subjects in the study and for averages). It’s actually pretty shocking to me that in a longitudinal analysis, such graphs are not shown.
Andrew, it doesn't look like they are talking about "knowing" words in the sense of a vocabulary test, just "recalling" words in a list that is read to you.
However, your main point is still valid: if the better-educated people had better recall at the start of the study, they might be as good or better than the other people at the end even if they had a steeper decline.
It's also worth pointing out that (all other things being equal) realistic models of memory predict that retrieval is harder and slower the more you know. It is easy to think of in terms of serial search (but it applies to parallel search too): if you have to find item x in a pool of N items – it'll be easier to find if N = 10 than if N = 100.
It's quite simple: Jeanna Bryner either didn't understand the study, or else purposefully extracted one result and misrepresented it.