It’s kissing. Saved you a click.

Five seconds or less is a huge smallest bucket for kiss duration! At the five-second threshold you're already entering make-out territory.

Plus, people whose kisses average one second are having a very different experience than those who average around four seconds.

Seems like a poorly-designed statistic to me. I wonder if they felt they needed such coarse granularity because the data is collected by survey and people struggle to bucket themselves well.

I think it's not any one stand-alone thing, but the sum total. Is kissing important? Probably, but also not much value without deep, meaningful conversation. Conversely, deep, meaningful conversation without physical connection also starts to ring hollow.