“…However, HRG does not have predictive power (as β and γ incorporate the dependent variable, namely the change in average trait value over one generation) [29, 40, 41], and does not account for non-vertical transmission of altruism (but see [42]). Studies of altruism as a cultural trait under non-vertical transmission have commonly used the frameworks of group selection [43, 44, 45, 46, 47] or network reciprocity [48, 49, 50, 51], as opposed to kin selection (but see [28, 52]). These studies have reached opposing conclusions on whether conformity—a type of non-vertical transmission that has been defined in different ways [53] but generally refers to a tendency to adopt more common variants—facilitates [43, 44, 49, 50, 51] or hinders [45, 48] the evolution of altruism.…”