Task Allocation and Partitioning of Social Insects - Network Representation of Tasks and Communication

Network Representation of Tasks and Communication

Numerous scientists have used a social network approach to model communication in animals, including that related to task performance. A network is pictorially represented as a graph, but can equivalently be represented as an adjacency list or adjacency matrix. Traditionally, workers are the nodes of the graph, but Fewell prefers to make the tasks the nodes, with workers as the links. O'Donnell has coined the term "worker connectivity" to stand for "communicative interactions that link a colony's workers in a social network and affect task performance". He has pointed out that connectivity provides three adaptive advantages compared to individual direct perception of needs:

1. It increases both the physical and temporal reach of information. With connectivity, information can travel farther and faster, and additionally can persist longer, including both direct persistence (i.e. through pheromones), memory effects, and by initiating a sequence of events.
2. It can help overcome task inertia and burnout, and push workers into performing hazardous tasks. For reasons of indirect fitness, this latter stimulus should not be necessary if all workers in the colony are highly related genetically, but that is not always the case.
3. Key individuals may possess superior knowledge, or have catalytic roles. Examples, respectively, are a sentry who has detected an intruder, or the colony queen.

O'Donnell provides a comprehensive survey, with examples, of factors that have a large bearing on worker connectivity. They include:

• graph degree
• size of the interacting group, especially if the network has a modular structure
• sender distribution (i.e. a small number of controllers vs. numerous senders)
• strength of the interaction effect, which includes strength of the signal sent, recipient sensitivity, and signal persistence (i.e. pheromone signal vs. sound waves)
• recipient memory, and its decay function
• socially-transmitted inhibitory signals, as not all interactions provide positive stimulus
• specificity of both the signal and recipient response
• signal and sensory modalities, and activity and interaction rates