<P> Quorum sensing can function as a collective decision - making process in any decentralised system . A quorum response has been defined as "a steep increase in the probability of group members performing a given behaviour once a threshold minimum number of their group mates already performing that behaviour is exceeded". A recent investigation showed that small groups of fish used consensus decision - making when deciding which fish model to follow . The fish did this by a simple quorum rule such that individuals watched the decisions of others before making their own decisions . This technique generally resulted in the' correct' decision but occasionally cascaded into the' incorrect' decision . In addition, as the group size increased, the fish made more accurate decisions in following the more attractive fish model . Consensus decision - making, a form of collective intelligence, thus effectively uses information from multiple sources to generally reach the correct conclusion . Such behaviour has also been demonstrated in the shoaling behaviour of threespine sticklebacks . </P> <P> Other open questions of shoaling behaviour include identifying which individuals are responsible for the direction of shoal movement . In the case of migratory movement, most members of a shoal seem to know where they are going . Observations on the foraging behaviour of captive golden shiner (a kind of minnow) found they formed shoals which were led by a small number of experienced individuals who knew when and where food was available . If all golden shiners in a shoal have similar knowledge of food availability, there are a few individuals that still emerge as natural leaders (being at the front more often) and behavioural tests suggest they are naturally bolder . Smaller golden shiners appear more willing than larger ones to be near the front of the shoal, perhaps because they are hungrier . Observations on the common roach have shown that food - deprived individuals tend to be at the front of a shoal, where they obtain more food but where they may also be more vulnerable to ambush predators . Individuals that are wary of predation tend to seek more central positions within shoals . </P> <P> Experimental studies of shoal preference are relatively easy to perform . An aquarium containing a choosing fish is sandwiched between two aquaria containing different shoals, and the choosing fish is assumed to spend more time next to the shoal it prefers . Studies of this kind have identified several factors important for shoal preference . </P> <P> Fish generally prefer larger shoals . This makes sense, as larger shoal usually provide better protection against predators . Indeed, the preference for larger shoals seems stronger when predators are nearby, or in species that rely more on shoaling than body armour against predation . Larger shoals may also find food faster, though that food would have to be shared amongst more individuals . Competition may mean that hungry individuals might prefer smaller shoals or exhibit a lesser preference for very large shoals, as shown in sticklebacks . </P>

Why is it important to determine the location of shoaling areas