Neo-functionalist scholarship has made one of the first systematic attempts to explain why and under what circumstances regional organizations act cohesively in global forums. Known as the externalization hypothesis, Schmitter (1969; 1971) and Nye (1967; 1971) have argued that with progressive regional integration member states of a regional grouping tend to develop an interest in becoming a cohesive actor vis-à-vis third states. The motivation to centralize policies towards the extra-regional world is largely defensive: to safe-guard the economic benefits reaped from closer regional cooperation (Haas and Rowe 1973: 4), to reduce external dependence of member states and, at the same time, protect their foreign policy autonomy (ibid. 5). In a mutually reinforcing relationship, externalization is also believed to foster regional integration insofar as developing joint positions towards outsiders creates a need for increased internal consultation, communication, coordination, harmonization and, hence, institutionalization (ibid. 6). Externalization, in other words, has a dual effect: it helps to curtail the “exogenous determination of the external conditions of regional organizations” and, vice versa, creates conducive conditions for deepening regional integration (Schmitter 1971: 244; Jorgensen-Dahl 1977: 36).

In an empirical study Haas and Rowe tested eighteen regional organizations on externalization (Haas and Rowe 1973). In their research design they posited that primarily the material institutional properties such as functional specificity, homogeneity and autonomous central authority would influence the cohesiveness of regional organizations in global forums. The more functionally specific, the more homogenous the membership and the more centralized the organizational structure, they argued, the greater the likelihood is that a regional organization will act cohesively in global forums. By contrast, regional organizations with a broad functional scope, a diverse membership and a decentralized organizational structure are expected to be less united in global institutions. As the measure for cohesiveness they used the voting behavior of regional organizations in the United Nations General Assembly (ibid.).