It's obvious when you think about it, yet attention is often left out of media channel decisions. Professor Karen Nelson-Field says paying less for low engagement is a false economy.

Who cares if your ad appeared in front of someone if they didn't look at it?

Or, as happens more commonly, if they only glanced at it for a couple of seconds or less?

Professor Karen Nelson-Field is an attention specialist. Her work shows that the brand-building attention threshold - the point at which your advertising starts to work - is about 2.5 seconds, and that most digital video ads fail to make it.

How long your audience engages with your advertising directly relates to how long the impression lasts.

On average, each active attention second delivers around three days in memory. TV ads hold attention significantly longer, so they have a longer impact on sales than any other platform.

"I would pay more for programming with high attention, because the increase in engagement is worth paying more for," says Nelson-Field.

Procurement talks about the lowest cost media, but it's a false economy because the decrease in ROI us significantly more than the small increase in paying more for quality media."