Amplification mechanisms involved in group cohesion and coordination of several individuals' activities are a major research topic in social arthropod biology. In this paper, we investigate how recruitment processes can be mediated by the use of silk draglines in the case of social spiders. Our intent is to demonstrate how a behavioural feature common to all spider species can induce positive feedback, potentially leading to collective decision-making in a social context. Dragline-mediated amplification mechanisms are investigated in a simulated "Y" choice set-up. Numerical experiments involve two distinct models: a simplified one, devoted to the exploration of the most basic amplifying properties of the system, and a more complex simulation platform, taking into account the geometrical properties of a growing network (two-dimensional web). The effect of hypothetical subpopulations, as well as variations in silk attractivity in the case of mixed populations (originating from multiple nests) are also discussed. Results fit experimental data and demonstrate that spiders' behaviour exhibits very strong amplifying properties that can play a crucial part in the organization of social life. Copyright 1999 Academic Press.