We office workers may have lost hours of our lives listening to tedious, two-hour PowerPoint presentations by over-zealous management - and an Australian professor apparently agrees. He's dubbed Microsoft's presentation software a "disaster."

The reason, says Professor John Sweller at the University of New South Wales , is that the human brain is very good at absorbing information from a single source - from a written document, or by someone telling us something. Sweller's findings show that there are limits on the brain's capacity to process and retain information in short-term memory.

"It is effective to speak to a diagram, because it presents information in a different form. But it is not effective to speak the same words that are written, because it is putting too much load on the mind and decreases your ability to understand what is being presented," Sweller told Australian newspaper The Age .

Apple CEO Steve Jobs is famously good at giving presentations - his keynotes are strong on simple images, and simple, repeated phrases. You can see how effective this is by comparing Jobs' presentation style with that of Microsoft's Bill Gates.