In contrast, a genetic model of left-handedness needs to consider that it is polygenic; many genes play a role (Ocklenburg and co-workers, 2025). An important recent development in left-handedness research is the publication of the liability-threshold polygenic model of left-handedness by scientist Silvia Paracchini, a genetics researcher from the School of Medicine at the University of St Andrews in Scotland (Paracchini, 2024; Ocklenburg and co-workers, 2025, for an overview). The liability-threshold polygenic model of left-handedness now assumes that it is not one specific gene that determines handedness. If a person has enough of these left-handedness variants in their genome, they pass a developmental threshold that puts their brain on a developmental trajectory towards left-handedness. If a person has only a few or none of the left-handedness variants, they become right-handed.