The previous chapter looked at how information is transferred between individuals, in particular when they are looking for food. In one sense we can talk about individuals making decisions about where to collect food. The ants decide which of two food sources to exploit. Under natural conditions, however, food is often depleted or moves. As a result the available alternatives change and it is difficult to define when or if a decision has been made, or to even usefully talk about decisions between alternatives.
There are, however, many situations when animals have to decide between two or more options, whose qualities remain stable through time. This chapter focuses on such situations, where individuals have a number of options and where we can define an end point at which all individuals have made a choice. Most of the examples I consider in this chapter concern how groups choose a new shelter or migrate to a new home. Here we can sensibly talk about decision-making: once all individuals have settled at their new home or shelter, then we can say that a collective decision has been reached. The collective decision-making investigated in this chapter is thus information transfer in a specific, albeit interesting and important, setting. A setting in which there are multiple alternative choices available to a group, and the alternatives remain stable until a point at which we can say a decision has been made.
There are a number of important benefits to an individual in using the information possessed by others in reaching decisions (Sumpter & Pratt 2008). One benefit is the maintenance of cohesion. Choosing the same destination as others, for example, can make an animal less likely to be picked out by a predator. In the search for a new home there are often benefits to consensus, simply because group members do not want to have to invest time and effort re-coalescing because of an initial split.
While information transfer often results in cohesion, the underlying reason individuals followed or copied each other was not necessarily to promote group cohesion. Information transfer can be a form of social