A Test of Structural features of Granove~e~s Strength of weak Ties Theory*

GrunouetterS Strength of weak ties ’ theory offers a satisfying approach to the study of integration in networks of face-to-face interaction consisting of ~~~~tip~e subgroups. The present paper tests five hypotheses of this t~~eor,v in the setting of a n~~~t~dis~ip~inary social network of bioIogica1 scientists. Considerable support for the theory is indicated: the local bridges and inter-group ties in the network are disproportionately weak ties. Granovetter (1973) proposes a basis of inte~ation of a type of social structure whose integration previously has appeared problematical. The theory has received widespread attention’. However, the propositions for-warded by the theory still await systematic tests. Killworth and Bernard (1974~346) suggest that their evidence does not support the theory. Since Granovetter himself supports his propositions on the basis of ex post facto interpretations of previously published results, the present empirical status of the theory is uncertain, even as it has become increasingly entrenched in the sociological imagination. The theory most directly pertains to networks of face-to-face interaction. These networks often manifest a pattern of ties consisting of tight-knit clusters which are loosely coupled to each other; it is a pattern suggestive of local (intragroup) integration in combination with an anomy of the whole. Figure 1 illustrates the pattern. Granovetter’s theory rests on the idea that bridges (or local bridges) between cohesive clusters are important channels of information flow and bases of intergroup cohesion. In the graph analytic perspective, a bridge is a tie between two persons that is the sole path by means of which the two persons (and their direct contacts) are joined in a network (the definition of a local bridge is somewhat different and will be taken up later in the text}. The importance of bridges, of course, is that they represent the only possi-bility of a flow of information between two sets of persons. Granovette