more: A number who started off close to the bottom of the class ended up near the top.

''It was a massive effect,'' said Dr Alloway, who today gave a talk on working memory at the start of the British Science Festival at the University of Surrey in Guildford.

Video games that involve planning and strategy, such as those from the Total War series, may also train working memory, Dr Alloway believes.

''I'm not saying they're good for your socialisation skills, but they do make you use your working memory,'' she said.

''You're keeping track of past actions and mapping the actions you're going to take.''

cont: Sudoku also stretched the working memory, as did keeping up with friends on Facebook, she said.

But the ''instant'' nature of texting, Twitter and YouTube was not healthy for working memory.

''On Twitter you receive an endless stream of information, but it's also very succinct,'' said Dr Alloway. ''You don't have to process that information.

''Your attention span is being reduced and you're not engaging your brain and improving nerve connections.''

She said there was evidence linking TV viewing with Attention Deficit Hyperactivity Disorder (ADHD) while extensive texting was associated with lower IQ scores.

good clip cakebelly.

Good clip indeed, I'm beginning to think that twitter was designed for those who perhaps have the attention span of lint

"attention span of lint"

LINT: Little Intelligence Now Texting