Diverse populations make rational collective decisions -- ScienceDaily
The team found that individual ants had different yet consistent preferences. Some of the ants were happy to feed on either of the two solutions. Picky ants refused to feed from either. A third "middle" group consistently chose the solution with a higher concentration. These varied choices demonstrated that individual ants had individual thresholds to the sucrose concentration and made yes/no binary decisions accordingly.
The researchers then fed each colony again with the differing sucrose solutions and found that the majority of the ants in all six experimental colonies chose the 4.0% sucrose solution, without being influenced by other ants in the colony. The "collective" decision of the colony was thus for the more nourishing solution.
"Importantly, neither ants with a low threshold and high threshold contributed to the collective decision making, since the former didn't care about the concentration and the latter refused both concentrations. Thus, the decision maker was the middle group which preferred the higher concentration," says Hasegawa.
"The study demonstrates simple yes/no judgements by individuals can lead to a collective rational decision, without using quality-graded responses, when they have diverse thresholds in the population," he continued. This mechanism can be applied to various fields including brain science, behavioural science, swarm robotics and consensus decision-making in human societies, conclude the researchers.