"Compared to people getting seven hours of sleep, those who reported sleeping for nine hours made the same number of errors as people sleeping five or less."
This article does not mention when the attempted memorization occurred (before or after sleep).Nevertheless, short- vs. long-term memory is an important variable:
Re: https://science.howstuffworks.com/life/ ... emory2.htm
"Important information is gradually transferred from short-term memory into long-term memory. The more the information is repeated or used, the more likely it is to eventually end up in long-term memory. ... People tend to more easily store material on subjects that they already know something about, since the information has more meaning to them and can be mentally connected to related information that is already stored in their long-term memory."
Also, a person's sleep cycles may affect short-term memory such that the brain is not fully memory-able immediately after fewer or more hours of sleep (than the theorized seven). And as the second article mentions, what is being memorized affects test results* (some people may remember the test material better than others ... regardless of sleep excess or deprivation). 
* This suggests that EACH person tested should be tested days apart for memorization both with sleep deprivation and with sleep excess.
Rod
"individual users won’t be identified in the research" 
More like media twisting of fact, creating a "naughty nerdy moment". 
But still a good memory ...
(pointless if smartphone does the counting) 
