Research by a top human behaviour psychologist found A3 prints were really more impactful than A4. But it wasn't just by a whisker – the results of the study found images were up to 66 per cent more memorable.

Professor Richard Wiseman, from the University of Hertfordshire, undertook controlled experiments to find out if print size has an impact on how people respond to adverts and material such as charts and spreadsheets – and says he suspects A3 is probably the "sweet spot" size for prints.

The findings showed that people find products and services 43% more likeable and 30% better value for money when viewing them in A3. Adverts become 66% more memorable and 47% more impactful if they were printed in A3 rather than A4. Data was rather less at 22 per cent, but data rarely looks fantastic at any size, after all.

Psychological knock-on effects

Professor Wiseman commented that "you would perhaps expect an advert to have more impact in A3 over A4, but the psychological knock-on effects are really interesting, and they are not trivial. What struck me most was the size of the effects.

Wiseman was asked about even bigger sizes - would there still be the same results for A2 versus A3 for example? "I expect if you went to really large sizes the benefit may not be there. My gut feeling is that A3 would be a sweet spot, but I have no data for that."

Pressed if it was just because A3 prints basically looked better, he added "it's certainly more persuasive. Is it generally the case where you have bigger images? We don't know – there hasn't been much research so this is one of the key pieces of work out there.

"What's interesting is that visual impact translates to a psychological impact. The relatively small difference in size has a huge impact."