In the years immediately following the end of the Second World War, the world was swept by a wave of paranoia. The first rumblings of Cold War espionage were heard with suspicion falling on anyone wearing a long raincoat after dark. Alarmed citizens read of a new phenomenon called UFOs, and even something as seemingly harmless as the burgeoning new gadget, television, was cause for alarm.

Rumours had started to suggest that the television companies were allowing advertisers to flash 'buy our product' messages on the screen for a fraction of a second - not long enough for the viewer to see it, but just long enough for it to register in the brain. This led to an outcry with terms such as 'brainwashing' and 'mind control' being prominent. As a result, many states in the USA banned subliminal advertising on television. But subliminal messaging does have a harmless side, and one such way of using it is in a PowerPoint presentation.

I should make clear from the start, however, that this effect is best used as a light-hearted addition to a slide show, and therefore should not be used in a more serious presentation.

Here is a scenario of how a subliminal message could be used in a presentation.

After introducing himself to the audience, the presenter opens his slide show with a bit of fun. He says that you are supposed to be able to tell a man's status by the car he drives, and so invites the audience to guess which of the following three slides is a photograph of his own car.

Car A is an ordinary saloon, car B is a hatchback, and car C is a clapped out banger. As the slides are shown, the caption 'this one' appears for a split second on the slide of car B. After all three have been shown, the presenter asks for a show of hands for each car.

If there is a majority of raised hands for car B, then the presenter can explain how the audience was duped into making their selection because the instruction to choose that car had been flashed on the screen. If, on the other hand, car B does not perform very well in the vote, then this could be put down to the ineffectiveness of subliminal messaging. Either way, the use of a subliminal message has broken the ice and got the audience interacting with the presenter.

To include a subliminal message in your presentation, choose the slide on which you wish the message to appear and type your message into a text box. Adjust the size, colour and font and place the text where you want it to appear. Right click the text box and choose Custom Animation and then click on Entrance. Select Flash Once from the menu and click OK.

This new information will appear in the Custom Animation box on the right of the screen. Go to it and click the down arrow, then select Timing. This will open up the Custom Animation dialog box, and you can set the timing for when you want your message to appear and how long it will be visible for.

In the scenario above, the presenter might have selected the following settings from the Custom Animation dialog box:

Start: After Previous
Delay: 1 Second
Speed 0.5 seconds (Very Fast)
Repeat: (none)

This selection means that the message will flash once when the slide featuring car B is current. It will appear one second after the slide has been opened, and it will be displayed on the screen for half a second.

This is a novel way of injecting a little fun into a PowerPoint slide show. If the presentation is suitably light-hearted, fun aspects such as this can break the ice in putting the presenter at ease and making the audience more attentive. With features such as animations and sounds at your disposal, there is no limit to the amount of fun you can put into a presentation - but only if the situation warrants it.