. "Use it poorly and it can wither; work it well and it grows."
Teachers should also target working memory. As Dr Joni Holmes from the Cognition and Brain Sciences Unit in Cambridge explains: "We work with children with attention problems, and what we know is that they have really poor working memory skills. They find it hard to remember what the goal of the activity is. They forget what they're doing and appear as though they're distractible."
It is thought that we can hold up to seven things in our working memory at any one time, although a child of 4 may be able to manage only two or three. Our working memory capacity may be up to 50 per cent inherited, but the good news is that we can all improve it, Holmes says. She has been testing computerised memory training - also known as brain training - with children completing working memory tasks every day. Feedback from teachers so far is that attention has improved as a result.
For those students with poor working memories, Holmes stresses the importance of reiterating the task in hand and fostering an environment where children feel it is OK to put up their hand and ask what they are meant to be doing, even if it's for the 10th time.
Hill says another area to review is the make-up of your lessons. Creating interesting, enjoyable tasks is an obvious way to maintain students' attention, but it is about more than just subject matter. The important thing is to use "as many different cognitive modalities as possible", Hill explains. This means visual prompts as well as verbal information, concrete aids to enhance abstract ideas and constant questioning of students.
"When you're doing a verbal introduction you really have to make sure that you've got the attention of all the children in the group," she advises.
Children with poor working memories can also benefit from props - a spelling sheet or Numicon blocks, for example - but beware, as too much stimulation can have a detrimental effect. For older learners dealing with essays and revision, Hill has a simple tip to pass on. "If you get to the bottom of the page and you can't remember what you've just read, you've tried to concentrate for too long. Look around, take your eye off the ball for a few minutes, then go back in," she suggests.
Holmes agrees: "Sometimes it's good to just stop and clear out your working memory and start again."
You could also reboot your students with a burst of physical exercise. In a 2010 study, children who took part in moderately intensive exercise for 15 minutes a day performed better in tests of concentration than those who didn't. The study's authors suggest it could be children's increasingly sedentary lifestyles, rather than advances in technology, that are to blame for shrinking attention spans (bit.lyExerciseStudy).
Hill also extols the virtues of making children aware of their thinking. "I would ask them: `How do you concentrate best? What are the things that make it more difficult for you?' " She has found that one of the key qualities of successful learners at primary school is that they will talk about the importance of listening and have strategies that help them to do so. With young children, Hill often works with an egg timer, rewarding those who can stay on task until the sand runs out and steadily increasing the time as the weeks go by.
So although concrete evidence about how attention spans are determined - and how long they should be - is absent, there are practical steps that teachers can take to assist students when attention begins to wane. The next time James' mind starts to wander, a short working memory exercise may be more appropriate than an hour's detention after school. Use the latter approach and after a few minutes he will probably forget why he's there.
Develop students' thinking skills with these matchstick puzzles.
Stimulate discussion with this PowerPoint full of intriguing questions.
Encourage pupils to make mental leaps with these thinking cards.