Every time an online user registers for a site or service, votes on an issue, or comments on a story he is demonstrating that he has understood something, not just seen it. This is the concept of cognition, which the Oxford Dictionary defines as "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses."

In the pecking order of metrics, cognition sits well above mere viewability, which does not guarantee that an ad is understood. But when an ad runs in most media, we can't know whether cognition occurred. We can know this only if a user takes a measurable action.

Marketers have been patient with us as an industry for way too long, as we have championed mindless "engagements" that will never move brand key performance indicators or satisfy lift goals. Instead, we should strive for "verified engagements," where a certified human audience comprehends a specific marketing message.

Like other agreed-upon metrics, a verified engagement (we could call it "digital cognition") must be measurable and confirmed by a third party. Whether that engagement is ultimately bucketed as awareness, recall, favorability or purchase intent is less of a concern.

Sadly, for all of today's digital tracking tools, analysis often stops at one-dimensional benchmarking. Many of the glaring questions have been removed from the equation. Was the ad message understood? Did we get what we paid for? Was the ad delivered to a human being?

Digital cognition -- if developed as a metric -- could answer these questions in combination, filling in the pieces of the brand-building process in a way that can't be achieved with a single-event measurement like the click-through rate. By demanding proof that a message was understood (that each engagement was verified and that spend was not wasted), brand marketers will be able to better control their budgets far into the future.

David Ogilvy once said, "You can't save souls in an empty church." To digital cognition, I think Ogilvy would have said, "Hallelujah."

Cognition, as a metric, is not yet in use. To be fair, it is very difficult to prove that message comprehension occurred. But could we develop a way to do it, the future of both online and mobile brand advertising would guarantee marketers and their agencies that real people are paying attention. The sooner we get there, the faster we'll see huge TV-like budgets in-play, digitally.