Are distracting smartphones making us more stupid? New research suggests that could be the case: When Carnegie Mellon researchers interrupted college students with text messages while they were taking a test, the students had average test scores that were 20 percent lower than the scores of those who took the exam with their phones turned off.

Another study found that students, when left to their own devices, are unable to focus on homework for more than two minutes without turning to Web surfing or e-mail. Adults in the workforce can make it to about 11 minutes.

Jennifer Roberts, a professor of the history of art and architecture at Harvard, thinks she has a fairly simple solution to help her American art history students appreciate the act of focusing: They must pick any painting, sculpture, or object made by an American artist and stare at it — for three hours.

“They’re usually skeptical at first,” she told me, “but afterward, they tell me the process was really astonishing, enabling them to see things, make observations, and develop original ideas about the work that never would have occurred otherwise.”

What a wonderful idea!

I'd probably only manage two and a half hours of Bosch's Last Judgement…before being classified as insane….maybe a wee bit longer on a Rothko! 

I suppose it changes with my mood, but right now I'd love to be spending three hours looking at Turner's Norham Castle with Sunrise. Just calm.

Paintings can also be responsible for changing your mood, after looking at them you can feel better or sometimes worse.

Indeed yes, a great idea!   Can't say I have done that, either -- unless staring at a fresco cycle in one chapel counts!!??  If so, surely I am not the only one: Pieros' frescoes in the chapel in San Francesco, Arezzo, the Masaccio and Masolino frescoes in the Carmine in Florence, or of course Giotto's Scrovegni chapel in Padua, for instance  (when they had no restrictions on time spent, which tells you this was a long time ago!!).  Or the Sistine chapel, but that really must count as a cheat!   However, does sculpture count for lists of the artworks to spend three hours staring at?  If so, I vote for Donatello's 'cantoria' from the cathedral, in the Museo di Santa maria del Fiore in Florence, and the same museum's Maria Magdalena also by Donatello.  Or if tapestry counts, would it be cheating to cite the huge "Maximilian" tapestry series in the Louvre and the even huger "Apocalypse" cycle in Angers?   Probably so, alas...

Just about your post on looking at a painting for three hours.  You might recall that in one of his books ('Looking at pictures' I think), Kenneth Clark says that the optimum period of time you can look at a picture is the time it would take you to peel and eat an orange.  I tend to agree.

I like the orange quotation - that's generally my view.  I've never spent three hours looking at a painting, but I've sometimes spent much longer than orange-time.  I think it takes the combination of a great picture and good viewing conditions.  I don't think your Rubens would work - that corridor in the NG is just not conducive to long looking.  Its pendant in the Wallace might be better.  I've spent a long time with some of the Poussins in the aptly named Orange Wing, and the great Rembrandt portraits of Jacob Trip and Margarethe de Geer.  And Piero della Francesca's Baptism.  Others that have engaged me for a long time are the awesome Velazquez Pope Innocent X in the Doria Pamphilj, the late Cezannes in Washington, Weyden's Deposition in the Prado, Bruegel's Hunters in the Snow.  Oddly some of my very favourite artists, like Raphael and Rubens, haven't inspired me to look for a very long time in a single sitting.