A small child stands, mesmerised by a poster. A lime green glow emerges from, what IS that? an egg? Silhouetted against the depths of space. Below it, eight words; In space, no one can hear you scream.
Why is this memory still so vivid decades (gulp) later? Why that poster and not the other 20+ on the platform that day?
I didn't see the groundbreaking x-rated sci-fi classic until many years later. I couldn't tell you who composed the score or whether it was being shown at the Odeon Gant's Hill. But I can remember the excitement, fear and trepidation that a particular combination of words and pictures had on me.
In any communication, how you make your audience feel is everything.
Above reason or logic. Above cold, hard facts. Although these are essential too.
Consider an awareness poster presenting the fact that one in three people develop some kind of cancer. It certainly makes a very persuasive rational argument. But it is the fear and concern felt by the reader that will really resonate and linger in the memory. It is the emotional response that will inspire them to live more healthily, or make that donation to the cancer charity.