Reading has required an ability to concentrate ever since writing was invented five thousand years ago. As such, reading on e-book devices can currently be classed as pseudo-reading, flitting or surfing from one page to the next. The reader's attention span is shortened, as reflected, for example, in the use of hypertext links. Digital reading has also changed our relationship with time, making it easier to access information, but not necessarily to memorise it. For the moment, most e-book devices also cause a certain degree of eye-strain. However, screen quality is constantly improving, suggesting that e-book devices may make print media obsolete in the near future.