Engaging emotions like love
Emotional engagement is easy to measure because modern society puts such a premium on not being emotional. Modern people put lots of effort into masking their emotional thoughts, and that effort is demonstrated in subtle behaviors called "psychomotor behavioral cues."
The stronger the emotional engagement the greater the masking effort and the more exaggerated these psychomotor behavioral cues become. These cues are easily measurable through different interfaces: browser, mobile, tablet, and more.
Someone may "like" your page, brand, or product, but if the accompanying cues aren't demonstrating an actual act of liking (genuine affection), then that person's click and your efforts pursuing them are worthless. (This is similar to the distinction between a "Facebook friend" and the friend you ask to be the best man at your wedding.)
But if someone both clicks "like" and demonstrates deep emotional cues (akin, for example, to a "love" relationship)? Reach out to them, and hurry!
Rewarding our predatory minds
Our minds use our predator wiring to achieve effort-based rewards in modern society.
The amount of effort can vary greatly: An endurance athlete may savor an energy drink at the end of a triathlon, while I'll savor a good cigar at the end of a long presentation.
But the effort is not nearly as important as the reward. The reward has to be psychologically commensurate (not physically commensurate) with the individual's concept of their effort (what's called a "fair-exchange"), and the reward has to be sensory in nature.
Do visitors put in lots of effort to convert on your digital property and are rewarded with a simple "Thank you?" Kiss those visitors good bye. Without a reward commensurate to effort, you'll lose them to competitors regardless of how much competitors reward them.
Is a lot of effort required, but the eventual reward is musical fanfare, dancers discoing across the screen, blinking lights, and a big, red "My God you're good!" moving from bottom left to upper right? Kiss those visitors hello.