The human brain naturally groups romantic partners together and searches for similarities, making couples appear more alike than they may objectively be. Rather than being a mystery, the phenomenon reflects how attraction, relationships, and perception interact throughout everyday life.

New global research reveals why couples who feel most alike aren't always the happiest — and what actually predicts lasting relationship satisfaction.

The human brain naturally groups romantic partners together and searches for similarities, making couples appear more alike than they may objectively be. Rather than being a…